{"id":385,"date":"2026-04-15T10:50:31","date_gmt":"2026-04-15T00:50:31","guid":{"rendered":"https:\/\/www.the-bach.kiwi\/?page_id=385"},"modified":"2026-05-08T13:56:16","modified_gmt":"2026-05-08T03:56:16","slug":"floating-service-ip-poor-mans-failover","status":"publish","type":"page","link":"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/","title":{"rendered":"Floating Service IP (Poor Man\u2019s Failover)"},"content":{"rendered":"\n<p>I wanted a file server that survives a host failure without touching clients, DNS, or rebuilding the network. This is the simplest pattern I know that works.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_83 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title ez-toc-toggle\" style=\"cursor:pointer\">Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#Context\" >Context<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%F0%9F%A7%A0-Concept\" >\ud83e\udde0 Concept<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%E2%9A%99%EF%B8%8F-Current-State\" >\u2699\ufe0f Current State<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%F0%9F%94%81-Manual-Failover-Procedure\" >\ud83d\udd01 Manual Failover Procedure<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#Step-1-%E2%80%94-Remove-service-IP-from-current-host\" >Step 1 \u2014 Remove service IP from current host<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#Step-2-%E2%80%94-Add-service-IP-to-target-host\" >Step 2 \u2014 Add service IP to target host<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#Step-3-%E2%80%94-Announce-ownership-IMPORTANT\" >Step 3 \u2014 Announce ownership (IMPORTANT)<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%E2%9A%A0%EF%B8%8F-Gotchas\" >\u26a0\ufe0f Gotchas<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%E2%9D%8C-Never-have-both-hosts-active-with-97\" >\u274c Never have both hosts active with .97<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%E2%9A%A0%EF%B8%8F-Without-arping\" >\u26a0\ufe0f Without arping<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%F0%9F%A7%A9-Why-This-Works\" >\ud83e\udde9 Why This Works<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%F0%9F%9A%80-Evolution-Path-Optional\" >\ud83d\ude80 Evolution Path (Optional)<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#1-Scripted-takeover\" >1. Scripted takeover<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#2-Health-based-failover\" >2. Health-based failover<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#3-Lightweight-HA\" >3. Lightweight HA<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%F0%9F%8E%AF-Design-Philosophy\" >\ud83c\udfaf Design Philosophy<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%F0%9F%A7%AD-Relationship-to-dv-gate\" >\ud83e\udded Relationship to dv-gate<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/#%F0%9F%A7%AA-Final-Thought\" >\ud83e\uddea Final Thought<\/a><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Context\"><\/span>Context<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>In a small home lab, high availability doesn\u2019t need Kubernetes, load balancers, or enterprise clustering.<\/p>\n\n\n\n<p>Sometimes you just need:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>a <strong>stable IP for a service<\/strong><\/li>\n\n\n\n<li>the ability to <strong>move it between hosts<\/strong><\/li>\n\n\n\n<li>and <strong>minimal moving parts<\/strong><\/li>\n<\/ul>\n\n\n\n<p>This pattern uses a <strong>floating service IP<\/strong> that can be manually (or later automatically) moved between nodes.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%F0%9F%A7%A0-Concept\"><\/span>\ud83e\udde0 Concept<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Separate <strong>host identity<\/strong> from <strong>service identity<\/strong>:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Type<\/th><th>Example IP<\/th><th>Purpose<\/th><\/tr><\/thead><tbody><tr><td>Host IP<\/td><td><code>172.17.20.253<\/code><\/td><td>Physical node (araman)<\/td><\/tr><tr><td>Host IP<\/td><td><code>172.17.20.254<\/code><\/td><td>Physical node (eldamar)<\/td><\/tr><tr><td>Service IP<\/td><td><code>172.17.20.97<\/code><\/td><td>File server (movable)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>Clients connect to:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>172.17.20.97 \u2192 file-server\n<\/code><\/pre>\n\n\n\n<p>They never need to know which machine is serving it.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E2%9A%99%EF%B8%8F-Current-State\"><\/span>\u2699\ufe0f Current State<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>On active node (e.g. <code>araman<\/code>):<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>ip -br addr\n<\/code><\/pre>\n\n\n\n<p>Shows:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>enp2s0 \u2192 172.17.20.253 (host)\n          172.17.20.97 (file-server)\n<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%F0%9F%94%81-Manual-Failover-Procedure\"><\/span>\ud83d\udd01 Manual Failover Procedure<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Step-1-%E2%80%94-Remove-service-IP-from-current-host\"><\/span>Step 1 \u2014 Remove service IP from current host<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>ip addr del 172.17.20.97\/24 dev enp2s0\n<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Step-2-%E2%80%94-Add-service-IP-to-target-host\"><\/span>Step 2 \u2014 Add service IP to target host<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>ip addr add 172.17.20.97\/24 dev enp2s0\n<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Step-3-%E2%80%94-Announce-ownership-IMPORTANT\"><\/span>Step 3 \u2014 Announce ownership (IMPORTANT)<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>arping -c 3 -A -I enp2s0 172.17.20.97\n<\/code><\/pre>\n\n\n\n<p>This forces:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>switches<\/li>\n\n\n\n<li>clients<\/li>\n\n\n\n<li>dv-gate<\/li>\n<\/ul>\n\n\n\n<p>\u2026to update their ARP tables immediately.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E2%9A%A0%EF%B8%8F-Gotchas\"><\/span>\u26a0\ufe0f Gotchas<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E2%9D%8C-Never-have-both-hosts-active-with-97\"><\/span>\u274c Never have both hosts active with <code>.97<\/code><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>If both nodes hold the IP:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>ARP flapping<\/li>\n\n\n\n<li>intermittent connections<\/li>\n\n\n\n<li>extremely confusing behaviour<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E2%9A%A0%EF%B8%8F-Without-arping\"><\/span>\u26a0\ufe0f Without <code>arping<\/code><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>Failover <em>will<\/em> appear broken for a while due to stale ARP caches.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%F0%9F%A7%A9-Why-This-Works\"><\/span>\ud83e\udde9 Why This Works<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>This leverages simple Layer 2 behaviour:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>IP \u2192 resolved to MAC via ARP<\/li>\n\n\n\n<li>whichever host responds becomes the owner<\/li>\n\n\n\n<li>updating ARP = redirecting traffic<\/li>\n<\/ul>\n\n\n\n<p>No routing changes required<br>No DNS changes required<br>No client changes required<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%F0%9F%9A%80-Evolution-Path-Optional\"><\/span>\ud83d\ude80 Evolution Path (Optional)<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>If this pattern proves useful, it can evolve into:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"1-Scripted-takeover\"><\/span>1. Scripted takeover<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>takeover-file-ip.sh\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"2-Health-based-failover\"><\/span>2. Health-based failover<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>ping checks<\/li>\n\n\n\n<li>service checks<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"3-Lightweight-HA\"><\/span>3. Lightweight HA<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>keepalived<\/code> (VRRP)<\/li>\n\n\n\n<li>floating virtual IP<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%F0%9F%8E%AF-Design-Philosophy\"><\/span>\ud83c\udfaf Design Philosophy<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>Keep the system understandable, observable, and recoverable.<\/p>\n<\/blockquote>\n\n\n\n<p>This approach is:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u2705 transparent<\/li>\n\n\n\n<li>\u2705 low dependency<\/li>\n\n\n\n<li>\u2705 easy to debug<\/li>\n\n\n\n<li>\u2705 easy to reverse<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%F0%9F%A7%AD-Relationship-to-dv-gate\"><\/span>\ud83e\udded Relationship to dv-gate<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>dv-gate<\/code> handles routing + NAT<\/li>\n\n\n\n<li>service IP floats <strong>within LAN only<\/strong><\/li>\n\n\n\n<li>no impact to WAN or firewall rules<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%F0%9F%A7%AA-Final-Thought\"><\/span>\ud83e\uddea Final Thought<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>This isn\u2019t enterprise HA.<\/p>\n\n\n\n<p>It\u2019s something better for a home lab:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>A system you can reason about at 2am when it breaks.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n","protected":false},"excerpt":{"rendered":"<p>I wanted a file server that survives a host failure without touching clients, DNS, or rebuilding the network. This is the simplest pattern I know that works. Context In a small home lab, high availability doesn\u2019t need Kubernetes, load balancers, or enterprise clustering. Sometimes you just need: This pattern uses a floating service IP that &#8230; <a title=\"Floating Service IP (Poor Man\u2019s Failover)\" class=\"read-more\" href=\"https:\/\/www.the-bach.kiwi\/index.php\/skunkworks\/floating-service-ip-poor-mans-failover\/\" aria-label=\"Read more about Floating Service IP (Poor Man\u2019s Failover)\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":359,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-385","page","type-page","status-publish"],"_links":{"self":[{"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/pages\/385","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/comments?post=385"}],"version-history":[{"count":4,"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/pages\/385\/revisions"}],"predecessor-version":[{"id":476,"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/pages\/385\/revisions\/476"}],"up":[{"embeddable":true,"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/pages\/359"}],"wp:attachment":[{"href":"https:\/\/www.the-bach.kiwi\/index.php\/wp-json\/wp\/v2\/media?parent=385"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}