{"id":1309,"date":"2026-04-21T04:46:12","date_gmt":"2026-04-21T04:46:12","guid":{"rendered":"https:\/\/www.vos3000.com\/blog\/?p=1309"},"modified":"2026-04-21T04:46:21","modified_gmt":"2026-04-21T04:46:21","slug":"vos3000-sip-send-unregister","status":"publish","type":"post","link":"https:\/\/www.vos3000.com\/blog\/vos3000-sip-send-unregister\/","title":{"rendered":"VOS3000 SIP Send Unregister: Essential Registration Cleanup Easy Guide"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\" id=\"vos-3000-sip-send-unregister-essential-registration-cleanup-guide\">VOS3000 SIP Send Unregister: Essential Registration Cleanup Guide<\/h1>\n\n\n\n<p>\ud83d\udd04 What happens when you restart your VOS3000 softswitch? Does the upstream SIP server still think you are registered, holding stale registration entries that could cause misrouted calls or ghost registrations? The answer depends on a single but critical parameter: <strong>SS_SIP_USER_AGENT_SEND_UNREGISTER<\/strong>, which controls the <strong>VOS3000 SIP send unregister<\/strong> behavior. When enabled (the default), VOS3000 sends a cancel register message to upstream servers during shutdown or restart \u2014 cleanly removing your registration state before the softswitch goes offline. \ud83d\udee1\ufe0f<\/p>\n\n\n\n<p>\ud83d\udce1 Whether you are performing scheduled maintenance, restarting services after configuration changes, or migrating your VOS3000 server to new hardware, the <strong>VOS3000 SIP send unregister<\/strong> parameter determines whether upstream carriers and SIP proxies receive proper notification that your registration is being withdrawn. Without this cleanup, the upstream server may continue routing calls to your softswitch for the duration of the remaining registration expiry \u2014 leading to failed calls, lost revenue, and confused SIP signaling states. This guide covers every aspect of the SS_SIP_USER_AGENT_SEND_UNREGISTER parameter, from its default On setting to related registration parameters like <strong>SS_SIP_USER_AGENT_EXPIRE<\/strong>, <strong>SS_SIP_USER_AGENT_RETRY_DELAY<\/strong>, and system-level parameters such as <strong>SS_ENDPOINT_REGISTER_REPLACE<\/strong>. \ud83c\udfaf<\/p>\n\n\n\n<p>\ud83d\udd27 All data in this guide is sourced exclusively from the official VOS3000 V2.1.9.07 Manual, Section 4.3.5.2 (Tables 4-3 and 4-4) \u2014 no fabricated values, no guesswork. For expert assistance with your VOS3000 deployment, contact us on WhatsApp at <strong>+8801911119966<\/strong>. \ud83d\udca1<\/p>\n\n\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Contents<\/h2><nav><ul><li><a href=\"#vos-3000-sip-send-unregister-essential-registration-cleanup-guide\">VOS3000 SIP Send Unregister: Essential Registration Cleanup Guide<\/a><ul><li><a href=\"#\ud83d\udd10-what-is-vos-3000-sip-send-unregister\">\ud83d\udd10 What Is VOS3000 SIP Send Unregister?<\/a><ul><li><a href=\"#\ud83c\udfaf-why-vos-3000-sip-send-unregister-matters\">\ud83c\udfaf Why VOS3000 SIP Send Unregister Matters<\/a><\/li><\/ul><\/li><li><a href=\"#\u2699\ufe0f-how-vos-3000-sip-send-unregister-works\">\u2699\ufe0f How VOS3000 SIP Send Unregister Works<\/a><ul><li><a href=\"#\ud83d\udd34-what-happens-when-ss-sip-user-agent-send-unregister-is-off\">\ud83d\udd34 What Happens When SS_SIP_USER_AGENT_SEND_UNREGISTER Is Off?<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udccb-related-sip-user-agent-registration-parameters\">\ud83d\udccb Related SIP User Agent Registration Parameters<\/a><ul><li><a href=\"#\ud83d\udd04-unregister-vs-registration-expiry-key-difference\">\ud83d\udd04 Unregister vs. Registration Expiry \u2014 Key Difference<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udd10-system-level-registration-parameters-that-affect-unregister-behavior\">\ud83d\udd10 System-Level Registration Parameters That Affect Unregister Behavior<\/a><\/li><li><a href=\"#\ud83d\udccb-registration-management-settings-in-vos-3000\">\ud83d\udccb Registration Management Settings in VOS3000<\/a><\/li><li><a href=\"#\ud83d\udd04-vos-3000-sip-send-unregister-complete-shutdown-scenario-analysis\">\ud83d\udd04 VOS3000 SIP Send Unregister \u2014 Complete Shutdown Scenario Analysis<\/a><ul><li><a href=\"#\ud83d\udce1-scenario-comparison-on-vs-off\">\ud83d\udce1 Scenario Comparison: On vs. Off<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udccb-step-by-step-vos-3000-sip-send-unregister-configuration\">\ud83d\udccb Step-by-Step VOS3000 SIP Send Unregister Configuration<\/a><ul><li><a href=\"#step-1-configure-global-ss-sip-user-agent-send-unregister-\ud83d\udccb\">Step 1: Configure Global SS_SIP_USER_AGENT_SEND_UNREGISTER \ud83d\udccb<\/a><\/li><li><a href=\"#step-2-configure-companion-registration-parameters-\ud83d\udd17\">Step 2: Configure Companion Registration Parameters \ud83d\udd17<\/a><\/li><li><a href=\"#step-3-configure-outbound-registration-in-gateway-\ud83d\udce1\">Step 3: Configure Outbound Registration in Gateway \ud83d\udce1<\/a><\/li><li><a href=\"#step-4-verify-with-sip-debug-\ud83d\udd0d\">Step 4: Verify with SIP Debug \ud83d\udd0d<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udcca-vos-3000-sip-send-unregister-best-practices-by-deployment\">\ud83d\udcca VOS3000 SIP Send Unregister Best Practices by Deployment<\/a><\/li><li><a href=\"#\ud83d\udee1\ufe0f-common-vos-3000-sip-send-unregister-problems-and-solutions\">\ud83d\udee1\ufe0f Common VOS3000 SIP Send Unregister Problems and Solutions<\/a><ul><li><a href=\"#\u274c-problem-1-cancel-register-message-not-received-by-upstream-server\">\u274c Problem 1: Cancel Register Message Not Received by Upstream Server<\/a><\/li><li><a href=\"#\u274c-problem-2-cancel-register-authentication-fails\">\u274c Problem 2: Cancel Register Authentication Fails<\/a><\/li><li><a href=\"#\u274c-problem-3-stale-registration-persists-after-abrupt-crash\">\u274c Problem 3: Stale Registration Persists After Abrupt Crash<\/a><\/li><li><a href=\"#\u274c-problem-4-multiple-vos-3000-instances-competing-for-same-registration\">\u274c Problem 4: Multiple VOS3000 Instances Competing for Same Registration<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udcde-complete-registration-parameter-quick-reference\">\ud83d\udcde Complete Registration Parameter Quick Reference<\/a><\/li><li><a href=\"#\ud83d\udca1-vos-3000-sip-send-unregister-configuration-checklist\">\ud83d\udca1 VOS3000 SIP Send Unregister Configuration Checklist<\/a><\/li><li><a href=\"#\u2753-frequently-asked-questions\">\u2753 Frequently Asked Questions<\/a><ul><li><a href=\"#\u2753-what-is-the-default-setting-for-vos-3000-sip-send-unregister\">\u2753 What is the default setting for VOS3000 SIP send unregister?<\/a><\/li><li><a href=\"#\u2753-when-should-i-set-ss-sip-user-agent-send-unregister-to-off\">\u2753 When should I set SS_SIP_USER_AGENT_SEND_UNREGISTER to Off?<\/a><\/li><li><a href=\"#\u2753-what-happens-to-the-cancel-register-if-vos-3000-crashes\">\u2753 What happens to the cancel register if VOS3000 crashes?<\/a><\/li><li><a href=\"#\u2753-does-the-cancel-register-message-require-authentication\">\u2753 Does the cancel register message require authentication?<\/a><\/li><li><a href=\"#\u2753-how-does-ss-sip-user-agent-expire-affect-the-unregister-behavior\">\u2753 How does SS_SIP_USER_AGENT_EXPIRE affect the unregister behavior?<\/a><\/li><li><a href=\"#\u2753-can-the-cancel-register-message-get-lost-in-transit\">\u2753 Can the cancel register message get lost in transit?<\/a><\/li><li><a href=\"#\u2753-what-is-the-sip-message-format-for-a-cancel-register\">\u2753 What is the SIP message format for a cancel register?<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udcda-related-resources\">\ud83d\udcda Related Resources<\/a><\/li><li><a href=\"#\ud83d\udcde-need-call-center-setup-support\">\ud83d\udcde Need Professional VOS3000 Setup Support?<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd10-what-is-vos-3000-sip-send-unregister\">\ud83d\udd10 What Is VOS3000 SIP Send Unregister?<\/h2>\n\n\n\n<p>\ud83d\udd04 The <strong>VOS3000 SIP send unregister<\/strong> feature controls whether VOS3000 sends a SIP REGISTER request with an expiration of zero (0) to upstream servers when the softswitch is stopping or restarting. This is commonly known as a &#8220;cancel register message&#8221; or &#8220;de-registration.&#8221; The parameter is governed by <strong>SS_SIP_USER_AGENT_SEND_UNREGISTER<\/strong> with a default value of <strong>On<\/strong> and two possible options: <strong>On<\/strong> or <strong>Off<\/strong>. \ud83d\udccb<\/p>\n\n\n\n<p>\ud83d\udccc According to the official VOS3000 V2.1.9.07 Manual, Table 4-3:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Attribute<\/th><th class=\"has-text-align-left\" data-align=\"left\">Value<\/th><\/tr><tr><td>\ud83d\udccc Parameter Name<\/td><td>SS_SIP_USER_AGENT_SEND_UNREGISTER<\/td><\/tr><tr><td>\ud83d\udd22 Default Value<\/td><td>On<\/td><\/tr><tr><td>\ud83d\udcd0 Options<\/td><td>On \/ Off<\/td><\/tr><tr><td>\ud83d\udcdd Description<\/td><td>Send Cancel Register Message<\/td><\/tr><tr><td>\ud83d\udccd Navigation<\/td><td>Operation management \u2192 Softswitch management \u2192 Additional settings \u2192 SIP parameter<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Key insight:<\/strong> This parameter applies specifically to VOS3000&#8217;s <em>outbound<\/em> SIP registration \u2014 when VOS3000 acts as a SIP User Agent registering <em>to<\/em> another server (such as an upstream carrier or SIP trunk provider). It does <em>not<\/em> control how VOS3000 handles inbound de-registrations from your own endpoints. For inbound registration handling, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-registration\/\" target=\"_blank\" rel=\"noopener\">VOS3000 SIP registration<\/a> configuration guide. \ud83d\udce1<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83c\udfaf-why-vos-3000-sip-send-unregister-matters\">\ud83c\udfaf Why VOS3000 SIP Send Unregister Matters<\/h3>\n\n\n\n<p>\u26a0\ufe0f Without proper unregister behavior, several critical problems can arise:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udcde <strong>Ghost registrations:<\/strong> Upstream servers retain stale registration entries, routing calls to a softswitch that is offline<\/li>\n\n\n\n<li>\ud83d\udd04 <strong>Misrouted incoming calls:<\/strong> Calls arrive at the upstream server, which forwards them to your old (now-offline) registration contact, resulting in call failures<\/li>\n\n\n\n<li>\ud83d\udee1\ufe0f <strong>Security stale state:<\/strong> Abandoned registration entries may linger for the full expiry duration, potentially exposing routing data<\/li>\n\n\n\n<li>\ud83d\udcca <strong>Billing discrepancies:<\/strong> Calls that fail due to stale registrations may still be billed by the upstream carrier if they consider the registration valid<\/li>\n\n\n\n<li>\u23f1\ufe0f <strong>Extended recovery time:<\/strong> After restart, VOS3000 must compete with its own stale registration on the upstream server before it can register cleanly<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u2699\ufe0f-how-vos-3000-sip-send-unregister-works\">\u2699\ufe0f How VOS3000 SIP Send Unregister Works<\/h2>\n\n\n\n<p>\ud83d\udd04 Understanding the unregister mechanism requires knowing how SIP registration and de-registration work at the protocol level. When SS_SIP_USER_AGENT_SEND_UNREGISTER is set to On, VOS3000 sends a REGISTER request with the Contact header Expires parameter set to 0 \u2014 this is the standard SIP mechanism for canceling a registration. \ud83d\udce1<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">\ud83d\udd04 VOS3000 SIP Send Unregister \u2014 Clean Shutdown Flow:\n\nVOS3000 \u2500\u2500\u2500\u2500 REGISTER (Expires: 3600) \u2500\u2500\u2500\u2500\u25ba Upstream SIP Server\n    \u2502                                           \u2502\n    \u2502\u25c4\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502 \u2705 Registered\n    \u2502                                           \u2502\n    \u2502   ... softswitch running normally ...     \u2502\n    \u2502                                           \u2502\n    \u2502   \u26d4 VOS3000 shutdown\/restart initiated   \u2502\n    \u2502                                           \u2502\nVOS3000 \u2500\u2500\u2500\u2500 REGISTER (Expires: 0) \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba Upstream SIP Server\n    \u2502       (Cancel Register Message)           \u2502\n    \u2502                                           \u2502\n    \u2502\u25c4\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502 \u2705 Registration removed\n    \u2502                                           \u2502\n    \u2502   \ud83c\udf89 Clean shutdown \u2014 no stale entries!   \u2502\n    \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n<\/pre>\n\n\n\n<p>\ud83d\udcca <strong>Key behavior:<\/strong> The cancel register message is sent <em>before<\/em> VOS3000 fully stops its SIP stack. This means the softswitch must still have network connectivity when the shutdown process begins. If VOS3000 is killed abruptly (power loss, kill -9), the unregister message may not be sent, regardless of the parameter setting. \u26a1<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udd34-what-happens-when-ss-sip-user-agent-send-unregister-is-off\">\ud83d\udd34 What Happens When SS_SIP_USER_AGENT_SEND_UNREGISTER Is Off?<\/h3>\n\n\n\n<p>\u26a0\ufe0f When this parameter is set to Off, VOS3000 simply stops without sending any cancel register message. The upstream server retains the registration entry until it naturally expires based on the <strong>SS_SIP_USER_AGENT_EXPIRE<\/strong> value. Here is the problematic scenario: \ud83d\udd27<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">\u26a0\ufe0f VOS3000 SIP Send Unregister OFF \u2014 Stale Registration Problem:\n\nVOS3000 \u2500\u2500\u2500\u2500 REGISTER (Expires: 3600) \u2500\u2500\u2500\u2500\u25ba Upstream SIP Server\n    \u2502                                           \u2502\n    \u2502\u25c4\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502 \u2705 Registered\n    \u2502                                           \u2502\n    \u2502   \u26d4 VOS3000 shutdown \u2014 NO unregister sent \u2502\n    \u2502                                           \u2502\n    \u2502   \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510 \u2502\n    \u2502   \u2502 Upstream server still has:          \u2502 \u2502\n    \u2502   \u2502 \ud83d\udccc Registration: VOS3000 \u2192 Active  \u2502 \u2502\n    \u2502   \u2502 \u23f1\ufe0f Expires in: ~3600 seconds        \u2502 \u2502\n    \u2502   \u2502 \ud83d\udcde Routing: Calls \u2192 VOS3000 IP      \u2502 \u2502\n    \u2502   \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518 \u2502\n    \u2502                                           \u2502\n    \u2502   Incoming call arrives \u2500\u2500\u25ba Routed to     \u2502\n    \u2502   offline VOS3000 \u2500\u2500\u25ba \u274c Call fails!      \u2502\n    \u2502                                           \u2502\n    \u2502   ... waiting for expiry (up to 3600s) ...\u2502\n    \u2502                                           \u2502\n    \u2502   \ud83d\udd04 VOS3000 restarts, sends new REGISTER \u2502\n    \u2502   \u2705 Registration restored (replaces old) \u2502\n    \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n<\/pre>\n\n\n\n<p>\ud83d\udca1 <strong>Critical observation:<\/strong> The duration of the stale registration depends on <strong>SS_SIP_USER_AGENT_EXPIRE<\/strong>. If the expiry is set to 3600 seconds (1 hour) and VOS3000 shuts down without sending unregister, the upstream server will consider the registration valid for up to 1 hour \u2014 during which all incoming calls to that registration will fail. For more on registration expiry, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-outbound-registration-sip\/\" target=\"_blank\" rel=\"noopener\">outbound registration SIP<\/a> guide. \ud83d\udce1<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udccb-related-sip-user-agent-registration-parameters\">\ud83d\udccb Related SIP User Agent Registration Parameters<\/h2>\n\n\n\n<p>\ud83d\udd17 The VOS3000 SIP send unregister parameter does not operate in isolation. It is part of a family of User Agent parameters that control outbound registration behavior. Understanding their interactions is essential for proper configuration. \ud83d\udee0\ufe0f<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Parameter<\/th><th class=\"has-text-align-left\" data-align=\"left\">Default<\/th><th class=\"has-text-align-left\" data-align=\"left\">Range \/ Options<\/th><th class=\"has-text-align-left\" data-align=\"left\">Description<\/th><\/tr><tr><td><strong>SS_SIP_USER_AGENT_SEND_UNREGISTER<\/strong><\/td><td><strong>On<\/strong><\/td><td><strong>On \/ Off<\/strong><\/td><td><strong>Send cancel register message on shutdown\/restart<\/strong><\/td><\/tr><tr><td>SS_SIP_USER_AGENT_EXPIRE<\/td><td>Auto Negotiation<\/td><td>20\u20137200s<\/td><td>SIP registration expiration time to other server<\/td><\/tr><tr><td>SS_SIP_USER_AGENT_RETRY_DELAY<\/td><td>60<\/td><td>30\u2013600s<\/td><td>Resend interval for SIP registration when failed<\/td><\/tr><tr><td>SS_SIP_USER_AGENT_PRIVACY<\/td><td>Ignore<\/td><td>Ignore \/ Id \/ None<\/td><td>Privacy setting for register user<\/td><\/tr><tr><td>SS_SIP_USER_AGENT_STOP_SWITCH_AFTER_INVITE_TIMEOUT<\/td><td>Off<\/td><td>On \/ Off<\/td><td>Stop switch gateway after INVITE timeout<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udccd All parameters are located at: <strong>Operation management \u2192 Softswitch management \u2192 Additional settings \u2192 SIP parameter<\/strong>. For the complete parameter reference, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-parameter-description\/\" target=\"_blank\" rel=\"noopener\">VOS3000 parameter description<\/a> guide. \ud83d\udcd6<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udd04-unregister-vs-registration-expiry-key-difference\">\ud83d\udd04 Unregister vs. Registration Expiry \u2014 Key Difference<\/h3>\n\n\n\n<p>\u26a0\ufe0f A common source of confusion is the difference between sending an unregister and letting a registration expire naturally. Here is the critical distinction: \ud83c\udfaf<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Aspect<\/th><th class=\"has-text-align-left\" data-align=\"left\">SIP Send Unregister (Expires: 0)<\/th><th class=\"has-text-align-left\" data-align=\"left\">Registration Natural Expiry<\/th><\/tr><tr><td>\ud83d\udccc Mechanism<\/td><td>Explicit REGISTER with Expires=0<\/td><td>No refresh sent; server times out<\/td><\/tr><tr><td>\u23f1\ufe0f Effectiveness<\/td><td>Immediate \u2014 server removes registration instantly<\/td><td>Delayed \u2014 server waits until expiry timer completes<\/td><\/tr><tr><td>\ud83d\udce1 Control<\/td><td>VOS3000 actively signals intent to unregister<\/td><td>VOS3000 passively allows registration to lapse<\/td><\/tr><tr><td>\ud83d\udee1\ufe0f Stale State Risk<\/td><td>None \u2014 registration removed on 200 OK<\/td><td>High \u2014 registration lingers until Expiry timer ends<\/td><\/tr><tr><td>\ud83d\udd27 Trigger<\/td><td>VOS3000 shutdown or restart (if parameter is On)<\/td><td>VOS3000 stops sending refresh REGISTER<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Simple rule:<\/strong> Sending unregister is an <em>active, immediate<\/em> cleanup. Letting registration expire is a <em>passive, delayed<\/em> cleanup. Always prefer active unregister for clean server state management. For more details on registration expiry, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-system-parameters\/\" target=\"_blank\" rel=\"noopener\">VOS3000 system parameters<\/a> reference. \ud83d\udce1<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd10-system-level-registration-parameters-that-affect-unregister-behavior\">\ud83d\udd10 System-Level Registration Parameters That Affect Unregister Behavior<\/h2>\n\n\n\n<p>\ud83d\udcca While SS_SIP_USER_AGENT_SEND_UNREGISTER controls the timing of VOS3000&#8217;s outbound de-registration, VOS3000 also provides system-level parameters that govern how inbound terminal registrations are handled. These are documented in Table 4-4 of the VOS3000 manual: \ud83d\udccb<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Parameter<\/th><th class=\"has-text-align-left\" data-align=\"left\">Default<\/th><th class=\"has-text-align-left\" data-align=\"left\">Description<\/th><\/tr><tr><td>SS_ENDPOINT_REGISTER_REPLACE<\/td><td>On<\/td><td>Allow replace current registered users when terminal registration<\/td><\/tr><tr><td>SS_ENDPOINT_REGISTER_RETRY<\/td><td>6<\/td><td>Max retry times when terminal registration<\/td><\/tr><tr><td>SS_ENDPOINT_REGISTER_SUSPEND<\/td><td>180<\/td><td>Disable duration after exceeding retry times<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udd27 <strong>How these relate to unregister:<\/strong> When VOS3000 restarts after a clean shutdown with unregister sent, and then sends a new REGISTER to the upstream server, <strong>SS_ENDPOINT_REGISTER_REPLACE<\/strong> (default: On) on the upstream side allows the new registration to replace any remaining stale entry. This is important because even with unregister sent, network conditions may cause the cancel register message to be lost. If SS_ENDPOINT_REGISTER_REPLACE is On on the receiving server, the new registration cleanly overrides the old one. \ud83d\udd11<\/p>\n\n\n\n<p>\ud83d\udcde For detailed configuration of endpoint registration behavior and suspension, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-authentication-suspend\/\" target=\"_blank\" rel=\"noopener\">VOS3000 authentication suspend<\/a> guide. For registration flood protection, refer to our <a href=\"https:\/\/multahost.com\/blog\/vos3000-registration-flood\/\" target=\"_blank\" rel=\"noopener\">VOS3000 registration flood<\/a> article. \ud83d\udcd6<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udccb-registration-management-settings-in-vos-3000\">\ud83d\udccb Registration Management Settings in VOS3000<\/h2>\n\n\n\n<p>\ud83d\udda5\ufe0f Beyond the SIP parameters, VOS3000 provides specific registration management settings for each outbound registration configured on the softswitch. These settings are documented on pages 106-107 of the VOS3000 manual and directly interact with the SS_SIP_USER_AGENT_SEND_UNREGISTER behavior: \ud83d\udce1<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Setting<\/th><th class=\"has-text-align-left\" data-align=\"left\">Options<\/th><th class=\"has-text-align-left\" data-align=\"left\">Relevance to Unregister<\/th><\/tr><tr><td>\ud83d\udce1 Signaling port<\/td><td>Configurable port number<\/td><td>Cancel register message uses the same signaling port<\/td><\/tr><tr><td>\ud83d\udda5\ufe0f Host name<\/td><td>FQDN or IP address<\/td><td>Identifies VOS3000 in the unregister Contact header<\/td><\/tr><tr><td>\ud83c\udf10 Sip proxy<\/td><td>Address of the SIP route<\/td><td>Cancel register is sent to the same SIP proxy<\/td><\/tr><tr><td>\ud83d\udccb Register period<\/td><td>Default or Auto negotiation<\/td><td>Determines how long stale registration persists if unregister fails<\/td><\/tr><tr><td>\ud83d\udd11 Authentication user<\/td><td>Username for SIP auth<\/td><td>Cancel register uses same credentials (401\/407 challenge-response)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Important note:<\/strong> The cancel register message must pass through the same SIP proxy and authenticate with the same credentials as the original registration. If authentication fails for the cancel register, the upstream server will not remove the registration entry, leaving a stale state. For more on SIP authentication, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-authentication\/\" target=\"_blank\" rel=\"noopener\">VOS3000 SIP authentication<\/a> guide. \ud83d\udd11<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd04-vos-3000-sip-send-unregister-complete-shutdown-scenario-analysis\">\ud83d\udd04 VOS3000 SIP Send Unregister \u2014 Complete Shutdown Scenario Analysis<\/h2>\n\n\n\n<p>\ud83d\udda5\ufe0f The behavior of VOS3000 during shutdown varies significantly based on how the softswitch is stopped and the state of SS_SIP_USER_AGENT_SEND_UNREGISTER. Here is a comprehensive analysis: \ud83c\udf10<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udce1-scenario-comparison-on-vs-off\">\ud83d\udce1 Scenario Comparison: On vs. Off<\/h3>\n\n\n\n<p>\ud83d\udcca Understanding the practical difference between the two settings requires examining what happens in various shutdown and restart scenarios: \ud83d\udccb<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Scenario<\/th><th class=\"has-text-align-left\" data-align=\"left\">SS_SIP_USER_AGENT_SEND_UNREGISTER = On<\/th><th class=\"has-text-align-left\" data-align=\"left\">SS_SIP_USER_AGENT_SEND_UNREGISTER = Off<\/th><\/tr><tr><td>\ud83d\udd27 Planned restart<\/td><td>\u2705 Cancel REGISTER sent \u2192 Clean removal<\/td><td>\u274c No cancel sent \u2192 Stale entry remains<\/td><\/tr><tr><td>\u26a1 Service crash<\/td><td>\u26a0\ufe0f Cancel may not be sent (no graceful shutdown)<\/td><td>\u26a0\ufe0f No cancel sent (same as On, since crash is ungraceful)<\/td><\/tr><tr><td>\ud83d\udd0c Power loss<\/td><td>\u274c Cancel cannot be sent<\/td><td>\u274c Cancel cannot be sent<\/td><\/tr><tr><td>\ud83d\udee1\ufe0f Network outage before shutdown<\/td><td>\u26a0\ufe0f Cancel sent but may not reach server<\/td><td>\u274c No cancel sent<\/td><\/tr><tr><td>\ud83d\udd04 Rapid restart (within seconds)<\/td><td>\u2705 Old registration removed, new one sent<\/td><td>\u26a0\ufe0f New REGISTER may conflict with stale entry<\/td><\/tr><tr><td>\ud83d\udccb Configuration change and restart<\/td><td>\u2705 Clean state for new configuration<\/td><td>\u274c Old registration may interfere with new settings<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83c\udfaf <strong>Conclusion:<\/strong> Keeping SS_SIP_USER_AGENT_SEND_UNREGISTER set to <strong>On<\/strong> (the default) is strongly recommended for all deployments. The only scenario where it provides no benefit is an abrupt crash or power loss \u2014 which is the same outcome as having it Off. In all planned shutdown and restart scenarios, On provides clean registration cleanup. For a complete SIP call flow reference, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-call-flow\/\" target=\"_blank\" rel=\"noopener\">VOS3000 SIP call flow<\/a> guide. \ud83d\udce1<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udccb-step-by-step-vos-3000-sip-send-unregister-configuration\">\ud83d\udccb Step-by-Step VOS3000 SIP Send Unregister Configuration<\/h2>\n\n\n\n<p>\u2699\ufe0f Follow these steps to configure the VOS3000 SIP send unregister parameter on your system:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-1-configure-global-ss-sip-user-agent-send-unregister-\ud83d\udccb\">Step 1: Configure Global SS_SIP_USER_AGENT_SEND_UNREGISTER \ud83d\udccb<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\ud83d\udd10 Log in to VOS3000 Client with administrator credentials<\/li>\n\n\n\n<li>\ud83d\udccc Navigate: <strong>Operation management \u2192 Softswitch management \u2192 Additional settings \u2192 SIP parameter<\/strong><\/li>\n\n\n\n<li>\ud83d\udd0d Locate <strong>SS_SIP_USER_AGENT_SEND_UNREGISTER<\/strong> in the parameter list<\/li>\n\n\n\n<li>\u270f\ufe0f Verify it is set to <strong>On<\/strong> (default) \u2014 this is the recommended setting<\/li>\n\n\n\n<li>\ud83d\udcbe Save and apply the changes<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-2-configure-companion-registration-parameters-\ud83d\udd17\">Step 2: Configure Companion Registration Parameters \ud83d\udd17<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\ud83d\udd0d Verify <strong>SS_SIP_USER_AGENT_EXPIRE<\/strong> \u2014 set registration expiry (default: Auto Negotiation, range: 20\u20137200s)<\/li>\n\n\n\n<li>\ud83d\udd0d Verify <strong>SS_SIP_USER_AGENT_RETRY_DELAY<\/strong> \u2014 set retry interval (default: 60, range: 30\u2013600s)<\/li>\n\n\n\n<li>\ud83d\udd0d Verify <strong>SS_SIP_USER_AGENT_PRIVACY<\/strong> \u2014 set privacy for register user (default: Ignore)<\/li>\n\n\n\n<li>\ud83d\udd0d Verify <strong>SS_SIP_USER_AGENT_STOP_SWITCH_AFTER_INVITE_TIMEOUT<\/strong> \u2014 gateway failover behavior (default: Off)<\/li>\n\n\n\n<li>\ud83d\udcbe Save all changes<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-3-configure-outbound-registration-in-gateway-\ud83d\udce1\">Step 3: Configure Outbound Registration in Gateway \ud83d\udce1<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\ud83d\udccc Navigate: <strong>Operation management \u2192 Softswitch management \u2192 Routing gateway<\/strong><\/li>\n\n\n\n<li>\ud83d\udd0d Select the gateway that requires outbound registration<\/li>\n\n\n\n<li>\ud83d\udd27 In gateway settings, configure:\n<ul class=\"wp-block-list\">\n<li>\ud83d\udce1 <strong>Sip proxy:<\/strong> Address of the SIP route (upstream server)<\/li>\n\n\n\n<li>\ud83d\udd11 <strong>Authentication user:<\/strong> Username for 401\/407 authentication<\/li>\n\n\n\n<li>\ud83d\udccb <strong>Register period:<\/strong> Default or Auto negotiation<\/li>\n\n\n\n<li>\ud83d\udda5\ufe0f <strong>Host name:<\/strong> FQDN or IP address of VOS3000<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\ud83d\udcbe Save gateway settings<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-4-verify-with-sip-debug-\ud83d\udd0d\">Step 4: Verify with SIP Debug \ud83d\udd0d<\/h3>\n\n\n\n<p>\ud83d\udcdd After configuration, verify the unregister behavior is working correctly by monitoring the SIP registration flow during a controlled restart. For comprehensive debugging techniques, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-troubleshooting-guide-2026\/\" target=\"_blank\" rel=\"noopener\">VOS3000 troubleshooting guide<\/a>. \ud83d\udd27<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">\ud83d\udcde Verifying VOS3000 SIP Send Unregister During Shutdown:\n\nVOS3000 \u2500\u2500\u2500\u2500 REGISTER (Expires: 3600) \u2500\u2500\u2500\u2500\u25ba Upstream Server\n    \u2502                                           \u2502\n    \u2502\u25c4\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502 \u2705 Active registration\n    \u2502                                           \u2502\n    \u2502   \u26d4 Administrator initiates VOS3000 stop \u2502\n    \u2502                                           \u2502\nVOS3000 \u2500\u2500\u2500\u2500 REGISTER (Expires: 0) \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba Upstream Server\n    \u2502       Contact: sip:user@vos3000-ip:5060   \u2502\n    \u2502       (Cancel Register Message)           \u2502\n    \u2502                                           \u2502\n    \u2502\u25c4\u2500\u2500\u2500\u2500 401 Unauthorized \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502 (auth challenge)\n    \u2502                                           \u2502\nVOS3000 \u2500\u2500\u2500\u2500 REGISTER (Expires: 0) \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba Upstream Server\n    \u2502       Authorization: Digest username=...  \u2502\n    \u2502       (Cancel with credentials)           \u2502\n    \u2502                                           \u2502\n    \u2502\u25c4\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502 \u2705 Registration removed!\n    \u2502                                           \u2502\n    \u2514\u2500\u2500 \ud83c\udf89 Clean shutdown confirmed \u2014 no stale entries\n<\/pre>\n\n\n\n<p>\ud83d\udca1 <strong>Verification tip:<\/strong> The cancel register message goes through the same authentication challenge (401\/407) as the original registration. This is standard SIP behavior \u2014 even de-registration requires proper authentication. If you see the REGISTER with Expires: 0 followed by a 200 OK in your SIP trace, the unregister is working correctly. \ud83d\udce1<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcca-vos-3000-sip-send-unregister-best-practices-by-deployment\">\ud83d\udcca VOS3000 SIP Send Unregister Best Practices by Deployment<\/h2>\n\n\n\n<p>\ud83c\udfaf Different VoIP deployment scenarios may have different requirements for unregister behavior. Here are our recommendations based on real-world deployment experience and VOS3000 manual specifications: \ud83d\udca1<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Deployment Type<\/th><th class=\"has-text-align-left\" data-align=\"left\">Recommended Setting<\/th><th class=\"has-text-align-left\" data-align=\"left\">Rationale<\/th><\/tr><tr><td>\ud83d\udcde Primary SIP trunk (carrier)<\/td><td>\u2705 On (default)<\/td><td>Essential \u2014 stale registrations cause incoming call failures during maintenance<\/td><\/tr><tr><td>\ud83c\udfe2 Enterprise SIP trunk<\/td><td>\u2705 On (default)<\/td><td>Clean state management prevents call routing confusion during restarts<\/td><\/tr><tr><td>\ud83c\udf0d Wholesale VoIP (multi-vendor)<\/td><td>\u2705 On (default)<\/td><td>Multiple upstream carriers must all receive clean unregister to avoid ghost routes<\/td><\/tr><tr><td>\ud83d\udce1 Backup\/secondary trunk<\/td><td>\u2705 On (default)<\/td><td>Even backup trunks should clean up registration to prevent call misrouting<\/td><\/tr><tr><td>\ud83d\udd04 High-availability cluster<\/td><td>\u2705 On (default)<\/td><td>Critical \u2014 failover depends on clean registration state transitions<\/td><\/tr><tr><td>\ud83e\uddea Test\/lab environment<\/td><td>\u26a0\ufe0f Off (optional)<\/td><td>May be disabled for testing registration expiry behavior and stale state scenarios<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\u26a0\ufe0f <strong>Strong recommendation:<\/strong> Keep SS_SIP_USER_AGENT_SEND_UNREGISTER set to <strong>On<\/strong> in all production deployments. The default setting is correct for virtually every scenario. Disabling it should only be done intentionally for testing purposes. For more on call routing strategies, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-call-routing\/\" target=\"_blank\" rel=\"noopener\">VOS3000 call routing<\/a> guide. \ud83d\udee1\ufe0f<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udee1\ufe0f-common-vos-3000-sip-send-unregister-problems-and-solutions\">\ud83d\udee1\ufe0f Common VOS3000 SIP Send Unregister Problems and Solutions<\/h2>\n\n\n\n<p>\u26a0\ufe0f Even with SS_SIP_USER_AGENT_SEND_UNREGISTER enabled, several issues can arise. Here are the most common problems and their solutions:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-1-cancel-register-message-not-received-by-upstream-server\">\u274c Problem 1: Cancel Register Message Not Received by Upstream Server<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> VOS3000 sends the unregister, but the upstream server still has the registration entry after VOS3000 restarts. Incoming calls may be routed to the old contact.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> Network conditions or firewall rules may prevent the cancel register message from reaching the upstream server. The unregister REGISTER with Expires: 0 may be lost due to UDP unreliability or blocked by a firewall during the shutdown sequence.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd27 Use TCP transport for SIP signaling if possible \u2014 ensures reliable delivery of the cancel register<\/li>\n\n\n\n<li>\ud83d\udce1 Check firewall rules to confirm that outbound SIP traffic is not blocked during the shutdown process<\/li>\n\n\n\n<li>\ud83d\udcca Verify that the cancel register reaches the upstream server using SIP debug traces<\/li>\n\n\n\n<li>\ud83d\udd04 After restart, the new REGISTER will replace the stale entry (if SS_ENDPOINT_REGISTER_REPLACE is On on the upstream server)<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-2-cancel-register-authentication-fails\">\u274c Problem 2: Cancel Register Authentication Fails<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> VOS3000 sends the cancel register, but receives a 403 Forbidden or repeated 401\/407 challenges that cannot be completed before shutdown finishes.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> The authentication credentials stored in VOS3000 may not match the upstream server&#8217;s current requirements, or the shutdown process does not allow enough time for the full authentication handshake.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd11 Verify the <strong>Authentication user<\/strong> credentials in the gateway configuration match the upstream server<\/li>\n\n\n\n<li>\ud83d\udcde Test registration manually before shutdown to confirm credentials are valid<\/li>\n\n\n\n<li>\ud83d\udccb Check that the SIP proxy address is correct and reachable<\/li>\n\n\n\n<li>\u23f1\ufe0f Ensure VOS3000 has enough time during shutdown to complete the authentication exchange<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-3-stale-registration-persists-after-abrupt-crash\">\u274c Problem 3: Stale Registration Persists After Abrupt Crash<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> VOS3000 crashes (process killed, power loss) and the upstream server retains the registration entry for the full expiry duration.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> An abrupt crash prevents VOS3000 from sending the cancel register message, regardless of the SS_SIP_USER_AGENT_SEND_UNREGISTER setting. This is an inherent limitation of the SIP protocol \u2014 there is no way to send an unregister after a crash.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u26a1 Use shorter <strong>SS_SIP_USER_AGENT_EXPIRE<\/strong> values (e.g., 300 seconds instead of 3600) to limit the maximum stale registration duration<\/li>\n\n\n\n<li>\ud83d\udd04 Configure <strong>SS_ENDPOINT_REGISTER_REPLACE<\/strong> (default: On) on the upstream server to allow new registration to override stale entries<\/li>\n\n\n\n<li>\ud83d\udee1\ufe0f Implement UPS (uninterruptible power supply) and process monitoring to prevent abrupt shutdowns<\/li>\n\n\n\n<li>\ud83d\udce1 Use <a href=\"https:\/\/multahost.com\/blog\/vos3000-call-routing\/\" target=\"_blank\" rel=\"noopener\">backup vendor gateways<\/a> so that calls continue through alternative paths while the stale entry expires<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-4-multiple-vos-3000-instances-competing-for-same-registration\">\u274c Problem 4: Multiple VOS3000 Instances Competing for Same Registration<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> Two VOS3000 instances register to the same upstream server with the same credentials. When one shuts down with unregister, it cancels the other instance&#8217;s registration.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> Both instances use the same SIP user credentials and register to the same SIP proxy. The cancel register from one instance removes the registration that the other instance depends on. \ud83d\udcca<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd11 Use different <strong>Authentication user<\/strong> credentials for each VOS3000 instance<\/li>\n\n\n\n<li>\ud83d\udda5\ufe0f Configure different <strong>Host name<\/strong> values to distinguish registrations<\/li>\n\n\n\n<li>\ud83d\udccb Use separate SIP proxy entries if the upstream server supports multiple registrations per account<\/li>\n\n\n\n<li>\ud83d\udee0\ufe0f For HA failover scenarios, disable unregister on the standby server to prevent accidental de-registration<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcde-complete-registration-parameter-quick-reference\">\ud83d\udcde Complete Registration Parameter Quick Reference<\/h2>\n\n\n\n<p>\ud83d\udcca Here is the complete reference for all parameters that govern SIP registration behavior in VOS3000 \u2014 both outbound (User Agent) and inbound (Endpoint): \ud83d\udccb<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Parameter<\/th><th class=\"has-text-align-left\" data-align=\"left\">Default<\/th><th class=\"has-text-align-left\" data-align=\"left\">Direction<\/th><th class=\"has-text-align-left\" data-align=\"left\">Function<\/th><\/tr><tr><td><strong>SS_SIP_USER_AGENT_SEND_UNREGISTER<\/strong><\/td><td><strong>On<\/strong><\/td><td><strong>Outbound<\/strong><\/td><td><strong>Send cancel register on shutdown\/restart<\/strong><\/td><\/tr><tr><td>SS_SIP_USER_AGENT_EXPIRE<\/td><td>Auto (20\u20137200s)<\/td><td>Outbound<\/td><td>Registration validity period<\/td><\/tr><tr><td>SS_SIP_USER_AGENT_RETRY_DELAY<\/td><td>60s<\/td><td>Outbound<\/td><td>Wait time before re-registering after failure<\/td><\/tr><tr><td>SS_SIP_USER_AGENT_PRIVACY<\/td><td>Ignore<\/td><td>Outbound<\/td><td>Privacy setting for register user<\/td><\/tr><tr><td>SS_SIP_USER_AGENT_STOP_SWITCH_AFTER_INVITE_TIMEOUT<\/td><td>Off<\/td><td>Outbound<\/td><td>Stop switch gateway after INVITE timeout<\/td><\/tr><tr><td>SS_ENDPOINT_REGISTER_REPLACE<\/td><td>On<\/td><td>Inbound<\/td><td>Allow replace current registered users<\/td><\/tr><tr><td>SS_ENDPOINT_REGISTER_RETRY<\/td><td>6<\/td><td>Inbound<\/td><td>Max retry times for terminal registration<\/td><\/tr><tr><td>SS_ENDPOINT_REGISTER_SUSPEND<\/td><td>180s<\/td><td>Inbound<\/td><td>Disable duration after exceeding retries<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udd27 For complete documentation on all SIP parameters, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-parameter-description\/\" target=\"_blank\" rel=\"noopener\">VOS3000 parameter description<\/a> reference. \ud83d\udcd6<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udca1-vos-3000-sip-send-unregister-configuration-checklist\">\ud83d\udca1 VOS3000 SIP Send Unregister Configuration Checklist<\/h2>\n\n\n\n<p>\u2705 Use this checklist when deploying or verifying your VOS3000 SIP send unregister settings:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Check<\/th><th class=\"has-text-align-left\" data-align=\"left\">Action<\/th><th class=\"has-text-align-left\" data-align=\"left\">Status<\/th><\/tr><tr><td>\ud83d\udccc 1<\/td><td>Verify SS_SIP_USER_AGENT_SEND_UNREGISTER is On (default) in SIP parameters<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 2<\/td><td>Set appropriate SS_SIP_USER_AGENT_EXPIRE (shorter = less stale time after crash)<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 3<\/td><td>Configure SS_SIP_USER_AGENT_RETRY_DELAY for post-restart re-registration timing<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 4<\/td><td>Verify Authentication user credentials match upstream server requirements<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 5<\/td><td>Test graceful shutdown and verify cancel register in SIP debug trace<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 6<\/td><td>Configure backup vendor gateways for failover during restart periods<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 7<\/td><td>Verify SS_ENDPOINT_REGISTER_REPLACE is On on upstream server (allows clean override)<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 8<\/td><td>Document expected stale registration window (based on EXPIRE value) for incident response<\/td><td>\u2610<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u2753-frequently-asked-questions\">\u2753 Frequently Asked Questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-is-the-default-setting-for-vos-3000-sip-send-unregister\">\u2753 What is the default setting for VOS3000 SIP send unregister?<\/h3>\n\n\n\n<p>\ud83d\udd04 The default setting for <strong>VOS3000 SIP send unregister<\/strong> is <strong>On<\/strong>, configured via the <strong>SS_SIP_USER_AGENT_SEND_UNREGISTER<\/strong> parameter. When set to On, VOS3000 automatically sends a cancel register message (REGISTER with Expires: 0) to all upstream SIP servers during a graceful shutdown or restart. This ensures that registration entries are removed from the upstream server immediately, preventing stale registration states and misrouted calls. The default On setting is recommended for all production deployments. \ud83d\udd27<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-when-should-i-set-ss-sip-user-agent-send-unregister-to-off\">\u2753 When should I set SS_SIP_USER_AGENT_SEND_UNREGISTER to Off?<\/h3>\n\n\n\n<p>\u26a0\ufe0f In virtually all production scenarios, you should keep this parameter at its default value of <strong>On<\/strong>. The only cases where you might consider setting it to Off are: (1) Testing environments where you want to observe stale registration behavior, (2) Troubleshooting upstream server registration replacement issues, or (3) Very specific carrier requirements where the upstream server does not support de-registration. Disabling unregister in production will cause stale registrations to persist after every restart, leading to call routing failures. For help evaluating your specific scenario, contact us on WhatsApp at <strong>+8801911119966<\/strong>. \ud83d\udce1<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-happens-to-the-cancel-register-if-vos-3000-crashes\">\u2753 What happens to the cancel register if VOS3000 crashes?<\/h3>\n\n\n\n<p>\u26a1 If VOS3000 crashes abruptly (power loss, kill -9, kernel panic), the cancel register message <em>cannot<\/em> be sent regardless of the SS_SIP_USER_AGENT_SEND_UNREGISTER setting. The unregister mechanism only works during a <em>graceful<\/em> shutdown where VOS3000 has time to send the REGISTER with Expires: 0 before the SIP stack stops. After an abrupt crash, the upstream server will retain the stale registration until the expiry timer (governed by SS_SIP_USER_AGENT_EXPIRE) elapses. Using shorter expiry values (e.g., 300s instead of 3600s) limits the maximum stale registration duration after a crash. \ud83d\udd27<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-does-the-cancel-register-message-require-authentication\">\u2753 Does the cancel register message require authentication?<\/h3>\n\n\n\n<p>\ud83d\udd11 Yes, the cancel register message (REGISTER with Expires: 0) typically goes through the same authentication process as a normal registration. When VOS3000 sends the cancel register, the upstream server will usually respond with a 401 Unauthorized or 407 Proxy Authentication Required challenge, and VOS3000 must resend the cancel register with proper credentials. This is standard SIP behavior per RFC 3261. The <strong>Authentication user<\/strong> configured in the gateway settings must match the upstream server&#8217;s requirements for the cancel register to succeed. For more on SIP authentication, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-authentication\/\" target=\"_blank\" rel=\"noopener\">VOS3000 SIP authentication<\/a> guide. \ud83d\udce1<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-how-does-ss-sip-user-agent-expire-affect-the-unregister-behavior\">\u2753 How does SS_SIP_USER_AGENT_EXPIRE affect the unregister behavior?<\/h3>\n\n\n\n<p>\u23f1\ufe0f The <strong>SS_SIP_USER_AGENT_EXPIRE<\/strong> parameter determines how long a successful registration remains valid on the upstream server. If VOS3000 shuts down without sending unregister (parameter Off or crash), the stale registration persists for the remaining expiry duration. With the default Auto Negotiation setting, the expiry is typically negotiated between VOS3000 and the upstream server within the range of 20\u20137200 seconds. Shorter expiry values mean stale registrations clear faster, while longer values increase the risk window. If you want to minimize stale registration impact, use a shorter fixed expiry (e.g., 300 seconds) and keep unregister On. \ud83d\udcca<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-can-the-cancel-register-message-get-lost-in-transit\">\u2753 Can the cancel register message get lost in transit?<\/h3>\n\n\n\n<p>\ud83d\udce1 Yes, since SIP commonly uses UDP transport, the cancel register message can be lost. If VOS3000 sends the cancel register but the upstream server never receives it, the registration entry will persist until the expiry timer elapses. To mitigate this: (1) Use TCP transport for SIP if supported by the upstream server, (2) Verify the cancel register reaches the server using SIP debug traces, (3) Configure backup vendor gateways so calls continue through alternative paths during the stale period, and (4) Rely on SS_ENDPOINT_REGISTER_REPLACE (On) on the upstream server to allow the new registration after restart to override any stale entry. For complete troubleshooting guidance, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-troubleshooting-guide-2026\/\" target=\"_blank\" rel=\"noopener\">VOS3000 troubleshooting guide<\/a>. \ud83d\udd27<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-is-the-sip-message-format-for-a-cancel-register\">\u2753 What is the SIP message format for a cancel register?<\/h3>\n\n\n\n<p>\ud83d\udccb A cancel register is a standard SIP REGISTER request with the Contact header Expires parameter set to 0. This tells the registrar server to remove the binding immediately. The message includes the same Call-ID, From tag, and To tag as the original registration (per RFC 3261 requirements for registration updates). VOS3000 handles this automatically when SS_SIP_USER_AGENT_SEND_UNREGISTER is On \u2014 no manual message construction is needed. For more on SIP message flows, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-call-flow\/\" target=\"_blank\" rel=\"noopener\">VOS3000 SIP call flow<\/a> guide. \ud83d\udca1<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcda-related-resources\">\ud83d\udcda Related Resources<\/h2>\n\n\n\n<p>\ud83d\udd17 Explore these related VOS3000 guides for comprehensive softswitch configuration:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udce1 <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-registration\/\" target=\"_blank\" rel=\"noopener\">VOS3000 SIP Registration<\/a> \u2014 Complete registration configuration and management<\/li>\n\n\n\n<li>\ud83d\udd11 <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-authentication\/\" target=\"_blank\" rel=\"noopener\">VOS3000 SIP Authentication<\/a> \u2014 401\/407 authentication setup and troubleshooting<\/li>\n\n\n\n<li>\ud83c\udf10 <a href=\"https:\/\/multahost.com\/blog\/vos3000-outbound-registration-sip\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Outbound Registration SIP<\/a> \u2014 Outbound registration to upstream carriers<\/li>\n\n\n\n<li>\ud83d\udcde <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-call-flow\/\" target=\"_blank\" rel=\"noopener\">VOS3000 SIP Call Flow<\/a> \u2014 Complete SIP signaling flow reference<\/li>\n\n\n\n<li>\ud83d\udccb <a href=\"https:\/\/multahost.com\/blog\/vos3000-parameter-description\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Parameter Description<\/a> \u2014 All SIP parameters documented<\/li>\n\n\n\n<li>\ud83d\udcca <a href=\"https:\/\/multahost.com\/blog\/vos3000-system-parameters\/\" target=\"_blank\" rel=\"noopener\">VOS3000 System Parameters<\/a> \u2014 System-level parameter reference<\/li>\n\n\n\n<li>\ud83d\udd04 <a href=\"https:\/\/multahost.com\/blog\/vos3000-call-routing\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Call Routing<\/a> \u2014 Routing and failover configuration<\/li>\n\n\n\n<li>\ud83d\udee1\ufe0f <a href=\"https:\/\/multahost.com\/blog\/vos3000-authentication-suspend\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Authentication Suspend<\/a> \u2014 Endpoint registration suspension behavior<\/li>\n\n\n\n<li>\ud83d\udce1 <a href=\"https:\/\/multahost.com\/blog\/vos3000-registration-flood\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Registration Flood<\/a> \u2014 Protection against registration flooding attacks<\/li>\n\n\n\n<li>\ud83d\udd27 <a href=\"https:\/\/multahost.com\/blog\/vos3000-troubleshooting-guide-2026\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Troubleshooting Guide<\/a> \u2014 Comprehensive debugging and diagnostics<\/li>\n\n\n\n<li>\ud83c\udfd7\ufe0f <a href=\"https:\/\/multahost.com\/blog\/vos3000-installation\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Installation<\/a> \u2014 Server setup and initial configuration<\/li>\n\n\n\n<li>\ud83d\udcb0 <a href=\"https:\/\/multahost.com\/blog\/vos3000-billing-system\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Billing System<\/a> \u2014 Billing and rating configuration<\/li>\n\n\n\n<li>\ud83d\uddc4\ufe0f <a href=\"https:\/\/multahost.com\/blog\/vos3000-data-maintenance\/\" target=\"_blank\" rel=\"noopener\">VOS3000 Data Maintenance<\/a> \u2014 Database maintenance and backup<\/li>\n\n\n\n<li>\ud83c\udf10 <a href=\"https:\/\/www.vos3000.com\/downloads.php\">VOS3000 Official Downloads<\/a> \u2014 Official software and documentation<\/li>\n<\/ul>\n\n\n\n<p>\ud83d\udcde Need expert help with your VOS3000 SIP send unregister configuration or registration cleanup? Contact us on WhatsApp at <strong>+8801911119966<\/strong> for professional assistance with your VoIP softswitch deployment. \ud83d\ude80<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcde-need-call-center-setup-support\">\ud83d\udcde Need Professional VOS3000 Setup Support?<\/h2>\n\n\n\n<p>For professional VOS3000 installations and deployment, VOS3000 Server Rental Solution:<\/p>\n\n\n\n<p>\ud83d\udcf1 <strong>WhatsApp:<\/strong> <a href=\"https:\/\/wa.me\/8801911119966\" target=\"_blank\" rel=\"noopener\">+8801911119966<\/a><br>\ud83c\udf10 <strong>Website:<\/strong> <a href=\"https:\/\/www.vos3000.com\">www.vos3000.com<\/a><br>\ud83c\udf10 <strong>Blog:<\/strong> <a href=\"https:\/\/multahost.com\/blog\" target=\"_blank\" rel=\"noopener\">multahost.com\/blog<\/a><br>\ud83d\udce5 <strong>Downloads:<\/strong> <a href=\"https:\/\/www.vos3000.com\/downloads.php\">VOS3000 Downloads<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><img decoding=\"async\" src=\"https:\/\/www.vos3000.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-1-1024x683.png\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive, VOS3000 SIP Resend Interval, VOS3000 SIP INVITE Timeout, VOS3000 SIP Call Progress Timeout, VOS3000 SIP Outbound Registration Parameters, VOS3000 SIP Privacy Header, VOS3000 SIP Routing Gateway Contact, VOS3000 SIP Publish Expire, VOS3000 SIP Display From, VOS3000 SIP Send Unregister\"><\/td><td><img decoding=\"async\" src=\"https:\/\/www.vos3000.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-1-1024x683.png\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive, VOS3000 SIP Resend Interval, VOS3000 SIP INVITE Timeout, VOS3000 SIP Call Progress Timeout, VOS3000 SIP Outbound Registration Parameters, VOS3000 SIP Privacy Header, VOS3000 SIP Routing Gateway Contact, VOS3000 SIP Publish Expire, VOS3000 SIP Display From, VOS3000 SIP Send Unregister\"><\/td><td><img decoding=\"async\" src=\"https:\/\/www.vos3000.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-1-1024x683.png\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive, VOS3000 SIP Resend Interval, VOS3000 SIP INVITE Timeout, VOS3000 SIP Call Progress Timeout, VOS3000 SIP Outbound Registration Parameters, VOS3000 SIP Privacy Header, VOS3000 SIP Routing Gateway Contact, VOS3000 SIP Publish Expire, VOS3000 SIP Display From, VOS3000 SIP Send Unregister\"><\/td><\/tr><\/tbody><\/table><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Master VOS3000 SIP send unregister with SS_SIP_USER_AGENT_SEND_UNREGISTER. Configure cancel register messages on restart, registration cleanup, and graceful shutdown for your VoIP softswitch.<\/p>\n","protected":false},"author":1,"featured_media":1296,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_kadence_starter_templates_imported_post":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[2],"tags":[7356,7306,7384,7360,7390,7366,7380,7358,6955,7363,7392,7361,7226,7374,7387,7377,7393,2647,7382,7010,6960,7388,7216,7367,7385,7389,7364,7357,7359,7375,7381,7383,7362,7391,7368,6954,7365,7376,7373,7212,7211,7370,7228,7371,7372,7369,7386,7378,7379],"class_list":["post-1309","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-vos3000","tag-ss_sip_user_agent_send_unregister","tag-vos3000-additional-settings-sip-parameter","tag-vos3000-authentication-user-registration","tag-vos3000-cancel-register-message","tag-vos3000-cancel-register-message-guide","tag-vos3000-cancel-register-on-stop","tag-vos3000-gateway-registration-cancel","tag-vos3000-graceful-shutdown-unregister","tag-vos3000-operation-management-sip-parameter","tag-vos3000-outbound-registration-cleanup","tag-vos3000-outbound-registration-sip","tag-vos3000-registration-cleanup","tag-vos3000-registration-flood-protection","tag-vos3000-registration-management-settings","tag-vos3000-registration-stale-entry","tag-vos3000-registration-stale-state","tag-vos3000-registration-state-cleanup","tag-vos3000-registration-troubleshooting","tag-vos3000-sip-call-flow-unregister","tag-vos3000-sip-parameter-configuration","tag-vos3000-sip-protocol-parameters","tag-vos3000-sip-proxy-cleanup","tag-vos3000-sip-proxy-registration","tag-vos3000-sip-register-expire-0","tag-vos3000-sip-registration-expire","tag-vos3000-sip-registration-restart","tag-vos3000-sip-registration-state-management","tag-vos3000-sip-send-unregister","tag-vos3000-sip-send-unregister-on-off","tag-vos3000-sip-server-state-management","tag-vos3000-sip-trunk-unregister","tag-vos3000-sip-unregister-best-practices","tag-vos3000-sip-unregister-on-restart","tag-vos3000-sip-user-agent-parameter","tag-vos3000-sip-user-agent-unregister","tag-vos3000-softswitch-management-sip","tag-vos3000-softswitch-registration-cleanup","tag-vos3000-softswitch-restart-behavior","tag-vos3000-ss_endpoint_register_replace","tag-vos3000-ss_endpoint_register_retry","tag-vos3000-ss_endpoint_register_suspend","tag-vos3000-ss_sip_user_agent_expire","tag-vos3000-ss_sip_user_agent_privacy","tag-vos3000-ss_sip_user_agent_retry_delay","tag-vos3000-ss_sip_user_agent_stop_switch_after_invite_timeout","tag-vos3000-unregister-upstream-server","tag-vos3000-voip-failover-unregister","tag-vos3000-voip-registration-cleanup","tag-vos3000-voip-softswitch-shutdown"],"acf":[],"jetpack_featured_media_url":"https:\/\/www.vos3000.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Routing-Gateway-Contact-VOS3000-SIP-Publish-Expire-VOS3000-SIP-Display-From-VOS3000-SIP-Send-Unregister.png","blog_post_layout_featured_media_urls":{"thumbnail":["https:\/\/www.vos3000.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Routing-Gateway-Contact-VOS3000-SIP-Publish-Expire-VOS3000-SIP-Display-From-VOS3000-SIP-Send-Unregister-150x150.png",150,150,true],"full":["https:\/\/www.vos3000.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Routing-Gateway-Contact-VOS3000-SIP-Publish-Expire-VOS3000-SIP-Display-From-VOS3000-SIP-Send-Unregister.png",1536,1024,false]},"categories_names":{"2":{"name":"VOS3000`","link":"https:\/\/www.vos3000.com\/blog\/category\/vos3000\/"}},"tags_names":{"7356":{"name":"SS_SIP_USER_AGENT_SEND_UNREGISTER","link":"https:\/\/www.vos3000.com\/blog\/tag\/ss_sip_user_agent_send_unregister\/"},"7306":{"name":"VOS3000 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