--- title: External Links on Spine Switches « ipSpace.net blog description: A networking engineer asked whether to connect a DC fabric's external links directly to spine switches or use dedicated border leaf switches when running EVPN... canonical: https://daily.dev/posts/external-links-on-spine-switches-ipspace-net-blog-ieequjnqh twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: External Links on Spine Switches « ipSpace.net blog | daily.dev og:description: A networking engineer asked whether to connect a DC fabric's external links directly to spine switches or use dedicated border leaf switches when running EVPN... og:url: https://daily.dev/posts/external-links-on-spine-switches-ipspace-net-blog-ieequjnqh og:image: https://api.daily.dev/og/posts/ieeqUjnQh.png og:image:alt: External Links on Spine Switches « ipSpace.net blog 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. # External Links on Spine Switches « ipSpace.net blog **[ipSpace.net Blog](https://daily.dev/sources/ipspace)** · 3 min read · 0 upvotes · 0 comments ## Summary A networking engineer asked whether to connect a DC fabric's external links directly to spine switches or use dedicated border leaf switches when running EVPN VXLAN. The answer depends on four key factors: number of spine nodes (load balancing implications), interface speeds (spines have high-speed ports that may not match WAN equipment), packet forwarding features (e.g., Broadcom Tomahawk spines cannot do VXLAN routing without recirculation), and buffer space requirements (WAN-facing switches need larger buffers for incast and speed disparity). The general recommendation is to use a dedicated pair of leaf switches for external connectivity, attaching network services like firewalls and load balancers there as well, since buying complex high-buffer spine switches is typically wasteful. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Should I connect external WAN links to spine switches or border leaf switches in an EVPN VXLAN data center fabric? In most cases, connecting external links to a dedicated pair of leaf (border) switches is better than using spine switches. Spine switches typically have high-speed but simple ASICs (e.g., Broadcom Tomahawk cannot do VXLAN routing without packet recirculation), smaller buffers ill-suited for WAN incast, and expensive high-speed interfaces that may not match WAN equipment. Dedicated border leaves also let you co-locate firewalls, load balancers, and storage. _Network engineers weighing this trade-off for upcoming fabric designs keep the discussion going on daily.dev._ ### Can Broadcom Tomahawk-based spine switches do VXLAN routing? Broadcom Tomahawk-based spine switches cannot perform VXLAN routing without packet recirculation. This is a hardware limitation of high-speed, simple-forwarding ASICs that most ASIC vendors use in spine-class switches. Juniper is noted as the only vendor known to have placed complex high-speed ASICs in spine switches, making most other vendors' spines unsuitable for VXLAN routing at the edge without a performance penalty. _Teams evaluating switching ASICs for VXLAN fabrics track vendor-specific limitations like this on daily.dev._ --- Tags: [#bgp](https://daily.dev/tags/bgp), [#networking](https://daily.dev/tags/networking) [View this post on daily.dev](https://daily.dev/posts/external-links-on-spine-switches-ipspace-net-blog-ieequjnqh) ```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":"External Links on Spine Switches « ipSpace.net blog","url":"https://daily.dev/posts/external-links-on-spine-switches-ipspace-net-blog-ieequjnqh","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/external-links-on-spine-switches-ipspace-net-blog-ieequjnqh"},"datePublished":"2026-08-11T08:56:16.121Z","dateModified":"2026-10-15T02:23:59.296Z","description":"A networking engineer asked whether to connect a DC fabric's external links directly to spine switches or use dedicated border leaf switches when running EVPN...","image":"https://media.daily.dev/image/upload/s--CxzD6vbw--/f_auto/v1722860399/public/Placeholder%2005","thumbnailUrl":"https://media.daily.dev/image/upload/s--CxzD6vbw--/f_auto/v1722860399/public/Placeholder%2005","isAccessibleForFree":true,"articleSection":"ipSpace.net Blog","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"ipSpace.net Blog","logo":"https://media.daily.dev/image/upload/s--xS7E82MT--/f_auto,q_auto/v1786438303/logos/ipspace?_a=BAMAMicg0","url":"https://daily.dev/sources/ipspace"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/external-links-on-spine-switches-ipspace-net-blog-ieequjnqh","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"bgp,networking","timeRequired":"PT3M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"ipSpace.net Blog","item":"https://daily.dev/sources/ipspace"},{"@type":"ListItem","position":3,"name":"External Links on Spine Switches « ipSpace.net blog"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/external-links-on-spine-switches-ipspace-net-blog-ieequjnqh#faq","mainEntity":[{"@type":"Question","name":"Should I connect external WAN links to spine switches or border leaf switches in an EVPN VXLAN data center fabric?","acceptedAnswer":{"@type":"Answer","text":"In most cases, connecting external links to a dedicated pair of leaf (border) switches is better than using spine switches. Spine switches typically have high-speed but simple ASICs (e.g., Broadcom Tomahawk cannot do VXLAN routing without packet recirculation), smaller buffers ill-suited for WAN incast, and expensive high-speed interfaces that may not match WAN equipment. Dedicated border leaves also let you co-locate firewalls, load balancers, and storage. Network engineers weighing this trade-off for upcoming fabric designs keep the discussion going on daily.dev."}},{"@type":"Question","name":"Can Broadcom Tomahawk-based spine switches do VXLAN routing?","acceptedAnswer":{"@type":"Answer","text":"Broadcom Tomahawk-based spine switches cannot perform VXLAN routing without packet recirculation. This is a hardware limitation of high-speed, simple-forwarding ASICs that most ASIC vendors use in spine-class switches. 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