--- title: Influence the Designated IS Election « IS-IS Labs description: A hands-on lab exercise covering IS-IS Designated Intermediate System (DIS) election on multi-access LAN segments. Explains why DIS stability matters —... canonical: https://daily.dev/posts/influence-the-designated-is-election-is-is-labs-lui7d3jcx twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Influence the Designated IS Election « IS-IS Labs | daily.dev og:description: A hands-on lab exercise covering IS-IS Designated Intermediate System (DIS) election on multi-access LAN segments. Explains why DIS stability matters —... og:url: https://daily.dev/posts/influence-the-designated-is-election-is-is-labs-lui7d3jcx og:image: https://api.daily.dev/og/posts/lUI7d3JcX.png og:image:alt: Influence the Designated IS Election « IS-IS Labs og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Influence the Designated IS Election « IS-IS Labs **[ipSpace.net Blog](https://daily.dev/sources/ipspace)** · 7 min read · 0 upvotes · 0 comments ## Summary A hands-on lab exercise covering IS-IS Designated Intermediate System (DIS) election on multi-access LAN segments. Explains why DIS stability matters — particularly on Carrier Ethernet deployments — and walks through configuring DIS election priority: raising it to 127 on hub routers and lowering it to 0 on spoke routers using the `isis priority` interface command. Also covers the two roles of the DIS (pseudonode advertisement and CSNP-based LSPDB synchronization), and why DIS failure can slow convergence when packet loss is present. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How does IS-IS elect the Designated Intermediate System on a LAN segment when all routers have the same priority? When all IS-IS routers on a segment share the same DIS election priority (default 64), the router with the highest MAC address becomes the DIS. Because MAC addresses tend to increase over time within the same vendor OUI, this typically means the most recently purchased router wins — which is often not the hub or most stable router in the network. _Network engineers tuning IS-IS convergence track DIS election behavior and related protocol changes on daily.dev._ ### What IS-IS DIS priority values should I set on hub and spoke routers to control which router becomes DIS? Set the hub router's DIS election priority to 127 (the maximum) and spoke routers to 0 (the minimum). The default priority is 64. The configuration uses an interface-level command such as `isis priority`. This guarantees the hub wins the election regardless of MAC address ordering, making DIS placement predictable and stable. _Keeping IS-IS lab configs and protocol best practices in one place is easier when you follow the networking content on daily.dev._ ### What happens to IS-IS network connectivity when the DIS fails on a LAN segment? A DIS failure causes no immediate connectivity loss because the pseudonode LSP remains in the LSPDB until a new DIS is elected and advertises a replacement pseudonode. However, if the segment experiences packet drops during the DIS-less interval, those dropped LSPs won't be retransmitted until the new DIS sends its first CSNP packet, which can delay convergence. _Engineers running IS-IS in large Carrier Ethernet deployments find protocol deep-dives like this through daily.dev._ --- [View this post on daily.dev](https://daily.dev/posts/influence-the-designated-is-election-is-is-labs-lui7d3jcx) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Influence the Designated IS Election « IS-IS Labs","url":"https://daily.dev/posts/influence-the-designated-is-election-is-is-labs-lui7d3jcx","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/influence-the-designated-is-election-is-is-labs-lui7d3jcx"},"datePublished":"2026-08-11T08:52:04.413Z","dateModified":"2026-08-11T08:55:00.490Z","description":"A hands-on lab exercise covering IS-IS Designated Intermediate System (DIS) election on multi-access LAN segments. 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