# IS-IS Published articles for IS-IS. This is one page of public article previews, not the complete archive. Follow Next page to continue. Summaries are not the original full articles. ## MPLS/VPN with SR-MPLS Core DevFeed: [MPLS/VPN with SR-MPLS Core]() Original publisher: [Read original article]() Published: 2026-09-15T05:45:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [SR-MPLS](), [MPLS VPN](), [networking](), [BGP](), [IS-IS](), [Network](), [GitHub]() Tags: [bgp](), [devices](), [github](), [is-is](), [mpls](), [mpls-vpn](), [netlab](), [sr-mpls](), [vpn]() ### AI overview This article explains how to build and test an MPLS/VPN service over an SR-MPLS core. It describes the required lab topology changes, including enabling MPLS/VPN, disabling LDP, configuring PE routers with IS-IS, SR-MPLS, BGP, MPLS, and VRF modules, and moving PE-to-host links into tenant VRFs. It also outlines how to run the lab using GitHub Codespaces, an Arista cEOS container, and netlab. ### Source excerpt As we discussed in the BGP-Free Core with SR-MPLS blog post, SR-MPLS works as a drop-in replacement for the traditional MPLS control plane. No wonder it works well (when properly implemented) with MPLS/VPN services - the second "fun" scenario in my ITNOG10 Segment Routing workshop. It uses the same topology as the BGP-Free Core scenario: Simplest possible MPLS/VPN network with SR-MPLS core Read more ... ## BGP-Free Core with SR-MPLS DevFeed: [BGP-Free Core with SR-MPLS]() Original publisher: [Read original article]() Published: 2026-09-03T05:30:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [SR-MPLS](), [BGP](), [networking](), [Network](), [Routing (disambiguation)](), [Containers](), [Linux](), [GitHub]() Tags: [bgp](), [containers](), [edge](), [examples](), [github](), [is-is](), [linux](), [mpls](), [netlab](), [network](), [router](), [routing](), [sr-mpls]() ### AI overview This article demonstrates how to build a BGP-free transport core with SR-MPLS using netlab. It describes a lab topology with IS-IS, BGP, Linux container hosts, and PE routers, then shows how SR-MPLS labels provide end-to-end connectivity without BGP routes on the core router. ### Source excerpt The beauty of SR-MPLS is that it's a drop-in replacement for the traditional (LDP- or RSVP-based) MPLS control plane. For example, you could replace LDP with SR-MPLS in a network using MPLS to implement a BGP-free transport core, and it just keeps working. This scenario was the first "fun" scenario in the ITNOG10 Segment Routing workshop. The core network uses the same topology as in the previous examples; I added two hosts and BGP routing. Simplest possible network using a BGP-free core Read more ... ## Multivendor SR-MPLS DevFeed: [Multivendor SR-MPLS]() Original publisher: [Read original article]() Published: 2026-08-25T05:44:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [SR-MPLS](), [networking](), [Routing (disambiguation)](), [IS-IS](), [GitHub]() Tags: [github](), [installation](), [is-is](), [mpls](), [netlab](), [network](), [routing](), [sr-mpls]() ### AI overview This tutorial demonstrates a multivendor SR-MPLS network built with netlab using Arista EOS, FRRouting, and SR Linux. It explains vendor-specific Segment Routing Global Block ranges, prefix segments, and MPLS LFIB label swapping, then outlines how to launch the lab through GitHub Codespaces. ### Source excerpt Summer is almost over, and it's time to resume regular programming with the next example from the Segment Routing workshop I had at ITNOG10: multi-vendor SR-MPLS. I used the same lab topology as in the previous examples but deployed Arista EOS on PE1, FRRouting on P, and SR Linux on PE21 Read more ... ## The Never-Ending IPv6 Loopback Prefix Saga DevFeed: [The Never-Ending IPv6 Loopback Prefix Saga]() Original publisher: [Read original article]() Published: 2026-08-17T06:02:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [Network](), [Hardware](), [datacenter](), [BGP]() Tags: [bgp](), [datacenter](), [hardware](), [ios](), [ipv6](), [is-is](), [netlab](), [network](), [ospf](), [vxlan]() ### AI overview The article examines the IPv6 loopback-prefix problem in high-speed routers and data-center switches. OSPFv3 requires loopbacks to be advertised as /128s, which can increase forwarding hardware demands when /64 addressing is preferred. It compares vendor behaviors and suggests IS-IS or BGP as possible alternatives. ### Source excerpt Remember the sage advice to simplify your life and use the IPv6 /64 prefixes everywhere? Not only does it make your life simpler (and wastes immesuarably less address space than the crazy "let's assign /64 to every device" stupidity), it also reduces the hardware requirements in your high-speed routers layer-3 switches. You see, doing lookups on 64 bits uses half the silicon it takes to do lookups on 128 bits. Alas, some people never got the memo. OSPFv3 standard clearly states in one of the bullets in section 4.4.3.9 that the loopback prefixes should always be advertised as /128s regardless of what's configured on the interface. Read more ... ## SR-MPLS with OSPFv2 DevFeed: [SR-MPLS with OSPFv2]() Original publisher: [Read original article]() Published: 2026-06-15T06:12:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [SR-MPLS](), [networking](), [Routing (disambiguation)](), [Protocol (disambiguation)](), [IS-IS](), [GitHub]() Tags: [container](), [github](), [is-is](), [mpls](), [netlab](), [ospf](), [protocol](), [routing](), [sr-mpls]() ### AI overview A hands-on tutorial showing how to configure and inspect SR-MPLS over OSPFv2 with netlab. It explains the OSPFv2 opaque LSAs used to advertise SR-MPLS information and notes that the resulting MPLS forwarding table matches the comparable IS-IS example. ### Source excerpt I started my part of the Segment Routing workshop @ ITNOG10 exploring SR-MPLS with IS-IS (simple SR-MPLS, dual-stack SR-MPLS, SR-MPLS over unnumbered IPv4 interfaces). Next step: let's change the routing protocol to OSPF while using the same network topology: Read more ... ## SR-MPLS over Unnumbered Interfaces DevFeed: [SR-MPLS over Unnumbered Interfaces]() Original publisher: [Read original article]() Published: 2026-06-01T06:03:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [SR-MPLS](), [IS-IS](), [networking](), [Protocol (disambiguation)]() Tags: [container](), [demo](), [examples](), [github](), [implementation](), [installation](), [interfaces](), [ipv4](), [is-is](), [mpls](), [netlab](), [network](), [protocol](), [routing](), [sr-mpls](), [traffic-engineering]() ### AI overview This tutorial demonstrates SR-MPLS over unnumbered IPv4 point-to-point interfaces using netlab and IS-IS. It explains the resulting SR-MPLS and IS-IS advertisements, including adjacency and prefix segments, and provides steps for trying the lab through GitHub Codespaces and an Arista cEOS container. ### Source excerpt After the simple SR-MPLS demo and the dual-stack SR-MPLS setup, it was time for the next obvious question: Does SR-MPLS work over unnumbered IPv4 interfaces1, assuming the implementation of the underlying routing protocol supports them? Of course it does; let's go through the details, using the same topology I used throughout the Segment Routing workshop @ ITNOG10. Read more ... ## Dual-Stack SR-MPLS DevFeed: [Dual-Stack SR-MPLS]() Original publisher: [Read original article]() Published: 2026-05-21T06:16:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [SR-MPLS](), [networking](), [IS-IS](), [Routing (disambiguation)](), [Demo](), [GitHub]() Tags: [github](), [implement](), [ipv4](), [ipv6](), [is-is](), [links](), [mpls](), [netlab](), [network](), [router](), [routing](), [space](), [sr-mpls]() ### AI overview This tutorial demonstrates a dual-stack SR-MPLS lab built with netlab. It explains IPv4 and IPv6 SID addressing, loopback and core-link address pools, and the resulting IS-IS and MPLS forwarding-table entries. ### Source excerpt After the introduction to SR-MPLS demo I did during the Segment Routing workshop @ ITNOG10, we moved to dual-stack SR-MPLS - can we assign node segment identifiers (SIDs) to IPv4 and IPv6 prefixes? The demo used the same three-router network as the previous one, with IPv4 SIDs starting at one and IPv6 SIDs starting at 101: Read more ... ## netlab 26.05: BGP-free SRv6 Core, Junos Features DevFeed: [netlab 26.05: BGP-free SRv6 Core, Junos Features]() Original publisher: [Read original article]() Published: 2026-05-19T06:02:00Z Content type: release Language: en Sources: [ipSpace.net blog]() Topics: [BGP](), [SRv6](), [releases](), [IS-IS](), [configuration]() Tags: [bgp](), [configuration](), [devices](), [is-is](), [netlab](), [release](), [release-notes](), [srv6]() ### AI overview The netlab 26.05 release adds support for global BGP routes with SRv6 next hops on FRR and IOS XR, several Junos OSPF and IS-IS capabilities, FortiOS configuration improvements, and Juniper cSRX container support. It also updates scripting, restart, configuration collection, reload testing, topology graph definitions, and multilab operation handling. ### Source excerpt netlab release 26.05 is out. Here are the highlights: Support for global BGP routes with SRv6 next hops (inspired by proof-of-concept by @jvbemmel) on FRR and IOS XR Junos OSPF/IS-IS route redistribution, VRF IS-IS instances, and OSPF interface parameters Streamline and speed up the FortiOS initial device configuration by @a-v-popov Support for Juniper cSRX container by @leec-666 Read more ... ## Hands-On Introduction to SR-MPLS DevFeed: [Hands-On Introduction to SR-MPLS]() Original publisher: [Read original article]() Published: 2026-05-13T06:16:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [SR-MPLS](), [networking](), [IS-IS](), [Routing (disambiguation)](), [Containers](), [GitHub]() Tags: [container](), [containers](), [github](), [is-is](), [netlab](), [network](), [router](), [routing](), [sr-mpls](), [x86]() ### AI overview A hands-on tutorial showing how to build and explore a small SR-MPLS network with netlab. It explains the topology, containerized Arista EOS routers, IS-IS and SR-MPLS configuration, and inspection of routing and MPLS forwarding state. ### Source excerpt The second demo1 I did during the Segment Routing workshop @ ITNOG10 illustrated how easy it is to set up and explore a small SR-MPLS network with netlab. The lab topology described a small three-router network (you need three routers to see "true" labels besides the penultimate-hop popping ones): Read more ... ## Lab: Summarizing IS-IS Level-1 Routes DevFeed: [Lab: Summarizing IS-IS Level-1 Routes]() Original publisher: [Read original article]() Published: 2026-04-03T07:02:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [networking](), [Routing (disambiguation)](), [Internet Engineering Task Force (IETF)]() Tags: [is-is](), [netlab](), [networking](), [protocol](), [routing]() ### AI overview This tutorial explains why IS-IS does not provide prefix summarization by default in IP networks and points readers to a lab for practicing Level-1 route summarization into the Level-2 backbone. ### Source excerpt IS-IS was designed to carry node addresses (NSAPs) between level-1 routers (called Intermediate Systems) within an area and area prefixes between level-2 routers, resulting in a perfect separation of concerns and forwarding information summarization. When IETF tried to use the same routing protocol for a networking stack with a completely different addressing mentality, something had to give. Read more ... ## netlab: Using L3VPN (MPLS/VPN) with SR-MPLS Core DevFeed: [netlab: Using L3VPN (MPLS/VPN) with SR-MPLS Core]() Original publisher: [Read original article]() Published: 2026-03-02T10:39:01Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [MPLS VPN](), [SR-MPLS](), [BGP](), [Containers](), [IS-IS](), [Linux](), [GitHub]() Tags: [bgp](), [containers](), [github](), [is-is](), [linux](), [mpls](), [mpls-vpn](), [netlab](), [sr-mpls]() ### AI overview This tutorial shows how to use netlab to build an MPLS/VPN lab with an SR-MPLS core. It describes a topology using Arista EOS cEOS containers, Linux containers, FRRouting containers, IS-IS, BGP, MPLS, SR-MPLS, and VRFs, and explains how to start the lab in a Linux VM, Windows Subsystem for Linux, a Mac with Apple Silicon, or GitHub Codespaces. ### Source excerpt Someone recently asked me whether it's possible to use netlab to build an MPLS/VPN (technically, BGP/MPLS IP VPN) lab with SR-MPLS core. Of course, let's build a simple lab using Arista EOS and Linux containers to implement this topology: Lab topology Here's the lab topology we'll use (also available on GitHub): Read more ... ## Lab: Build an SR-MPLS Network with IS-IS DevFeed: [Lab: Build an SR-MPLS Network with IS-IS]() Original publisher: [Read original article]() Published: 2026-02-13T07:02:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [SR-MPLS](), [Network](), [BGP](), [GitHub]() Tags: [bgp](), [github](), [is-is](), [netlab](), [network](), [sr-mpls]() ### AI overview A hands-on lab tutorial for configuring SR-MPLS with IS-IS and building a BGP-free core using netlab. It provides instructions for running the lab locally or through GitHub Codespaces. ### Source excerpt Want to spend an hour or two configuring some cool stuff this weekend? How about getting SR-MPLS to work with IS-IS and building a BGP-free core with it? If you already set up your own netlab environment, you probably know what to do (or you can get the details here). Alternatively, you can click here to start the lab in your browser using GitHub Codespaces. After starting the lab environment, change the directory to advanced/10-sr and execute netlab up. Read more ... ## Lab: Distributing Level-2 IS-IS Routes into Level-1 Areas DevFeed: [Lab: Distributing Level-2 IS-IS Routes into Level-1 Areas]() Original publisher: [Read original article]() Published: 2026-01-21T07:06:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [GitHub]() Tags: [browser](), [github](), [infrastructure](), [is-is](), [netlab](), [ospf](), [route]() ### AI overview This lab explains how IS-IS handles inter-area routes differently from OSPF. It explores distributing level-2 IS-IS routes into level-1 areas, including the default behavior and its consequences. ### Source excerpt One of the major differences between OSPF and IS-IS is their handling of inter-area routes. Non-backbone OSPF intra-area routes are copied into the backbone area and later (after the backbone SPF run) copied into other areas. IS-IS does not copy level-2 routes into level-1 areas; level-1 areas (by default) behave like totally stubby OSPF areas with the level-1 routers using the Attached (ATT) bit of level-1-2 routers in the same area to generate the default route. Read more ... ## Do You Need IS-IS Areas? DevFeed: [Do You Need IS-IS Areas?]() Original publisher: [Read original article]() Published: 2026-01-14T07:45:00Z Content type: opinion Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [networking](), [migration]() Tags: [github](), [is-is](), [network](), [networks](), [ospf](), [routing]() ### AI overview The article explains when IS-IS areas are useful. Most networks can likely operate with a single area, but hierarchy can help with fault isolation and route summarization, especially on constrained hardware. It recommends checking device capabilities because some implementations may not support inter-level prefix propagation. ### Source excerpt TL&DR: Most probably not, but if you do, you'd better not rely on random blogs for professional advice #justSaying 😜 Here's an interesting question I got from a reader in the midst of an OSPF-to-IS-IS migration: Why should one bother with different [IS-IS] areas when the routing hierarchy is induced by the two levels and the appropriate IS-IS circuit types on the links between the routers? Well, if you think you need a routing hierarchy, you're bound to use IS-IS areas because that's how the routing hierarchy is implemented in IS-IS. However... Read more ... ## Lab: Multilevel IS-IS Deployments DevFeed: [Lab: Multilevel IS-IS Deployments]() Original publisher: [Read original article]() Published: 2025-12-12T10:45:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [Scalability](), [GitHub](), [browser]() Tags: [browser](), [github](), [infrastructure](), [is-is](), [netlab](), [ospf](), [route](), [router](), [scalability]() ### AI overview This lab tutorial explains multilevel IS-IS, including its Level 1, Level 2, and Level 1-2 router roles and its scalability relationship to OSPF areas. It directs readers to a Multilevel IS-IS Deployments lab that can be started in a browser using GitHub Codespaces or local infrastructure with netlab. ### Source excerpt Like OSPF, IS-IS was designed when router memory was measured in megabytes and clock speeds in megahertz. Not surprisingly, it includes a scalability mechanism similar to OSPF areas. An IS-IS router could be a level-1 router (having in-area prefixes and a default route), a level-2 router (knowing just inter-area prefixes), or a level-1-2 router (equivalent to OSPF ABR). Even though multilevel IS-IS is rarely used today, it always makes sense to understand how things work, and the Multilevel IS-IS Deployments lab exercise created by Dan Partelly gives you a perfect starting point. Read more ... ## Lab: IS-IS Route Redistribution DevFeed: [Lab: IS-IS Route Redistribution]() Original publisher: [Read original article]() Published: 2025-11-28T06:45:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [GitHub](), [browser]() Tags: [browser](), [github](), [infrastructure](), [is-is](), [netlab](), [route](), [router]() ### AI overview This lab examines route redistribution into IS-IS, including how redistributed prefixes are included in router LSPs and how implementations use metric bits and TLVs. It also provides a safe environment for exploring LSP database contents. ### Source excerpt Route redistribution into IS-IS seems even easier than its OSPFv2/OSPFv3 counterparts. There are no additional LSAs/LSPs; the redistributed prefixes are included in the router LSP. Things get much more interesting once you start looking into the gory details and exploring how different implementations use (or do not) the various metric bits and TLVs. You'll find more details (and the opportunity to explore the LSP database contents in a safe environment) in the IS-IS Route Redistribution lab exercise. Read more ... ## IOS/XR Route Redistribution Configuration Mess DevFeed: [IOS/XR Route Redistribution Configuration Mess]() Original publisher: [Read original article]() Published: 2025-11-24T06:43:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [Cisco](), [Routing (disambiguation)](), [configuration](), [Network](), [BGP](), [IS-IS](), [networking]() Tags: [bgp](), [boot](), [cisco](), [configuration](), [is-is](), [netlab](), [network](), [ospf](), [protocol](), [routing](), [syntax](), [tests]() ### AI overview This article examines route redistribution on Cisco IOS/XR, showing that OSPFv2/OSPFv3, IS-IS, and BGP use inconsistent syntax for the source protocol in redistribute commands. The inconsistencies make reusable configuration templates more difficult to create. ### Source excerpt One would hope that the developers of a network operating system wouldn't feel the irresistible urge to reinvent what should have been a common configuration feature for every routing protocol. Alas, the IOS/XR developers failed to get that memo. I decided to implement route redistribution (known as route import in netlab) for OSPFv2/OSPFv3, IS-IS, and BGP on IOS/XR (Cisco 8000v running IOS/XR release 24.4.1) and found that each routing protocol uses a different syntax for the source routing protocol part of the redistribute command. Read more ... ## An MCP Agent for Querying Link-State Routing Graphs DevFeed: [An MCP Agent for Querying Link-State Routing Graphs]() Original publisher: [Read original article]() Published: 2025-11-19T06:15:00Z Content type: opinion Language: en Sources: [ipSpace.net blog]() Topics: [Model Context Protocol](), [Large Language Model](), [Graphs](), [networking](), [GitHub](), [IS-IS]() Tags: [ai](), [github](), [graphs](), [is-is](), [llm](), [mcp](), [network](), [routing]() ### AI overview The article highlights a demo that uses an LLM through an MCP agent to query collected link-state routing graphs. It points readers to the source code and related Topolograph, OSPF watcher, and IS-IS watcher projects. ### Source excerpt Vadim Semenov created a nice demo that allows you to use an LLM to query the collected link-state graphs through an MCP agent (SuzieQ would probably be faster and easier to deploy, but hey, AI). If you want to kick the tires, you'll find the source code on GitHub (Network AI assistant, MCP server for Topolograph service). You'll also need Vadim's previous projects: Topolograph and OSPF watcher or IS-IS watcher. ## netlab: Test IPv6 IGP Deployment DevFeed: [netlab: Test IPv6 IGP Deployment]() Original publisher: [Read original article]() Published: 2025-11-10T06:45:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [networking](), [Routing (disambiguation)](), [Deployment](), [Protocol (disambiguation)](), [Testing]() Tags: [container](), [container-image](), [containers](), [deployment](), [github](), [guide](), [install](), [installation](), [ipv6](), [is-is](), [netlab](), [ospf](), [protocol](), [router](), [routing](), [testing]() ### AI overview This tutorial shows how to use netlab to test IPv6 IGP deployments in a virtual lab. It explains how to add IPv6 prefixes while limiting OSPF deployment to OSPFv2 instead of configuring both OSPFv2 and OSPFv3, using a global address-family parameter. It also describes running the example with Arista cEOS containers or FRRouting in GitHub Codespaces. ### Source excerpt Imagine you have an IPv4-only network1 and want to try out how to deploy a routing protocol for IPv6. netlab is a pretty good tool for the job as it: Creates an addressing scheme for you Designs a routing protocol deployment (OSPF, IS-IS) based on just a few bits of information Deploys ready-to-run router configurations to a virtual lab. Read more ... ## Lab: Adjust IS-IS Timers DevFeed: [Lab: Adjust IS-IS Timers]() Original publisher: [Read original article]() Published: 2025-11-07T06:37:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [networking](), [Routing (disambiguation)](), [Protocol (disambiguation)](), [GitHub]() Tags: [github](), [infrastructure](), [is-is](), [netlab](), [network](), [protocol](), [routing](), [speed]() ### AI overview A lab exercise demonstrates how adjusting IS-IS timers can affect network convergence speed and stability. It recommends using BFD for fast convergence and provides instructions for launching the lab with GitHub Codespaces or local infrastructure using netlab. ### Source excerpt Like any other routing protocol, IS-IS has several timers you can tweak to improve the convergence speed of your network, or make your network unstable (eventually breaking it completely) if you reduce them too much (if you care about fast convergence, you REALLY SHOULD use BFD). You'll find more details (and the opportunity to tweak the timers in a safe environment) in the Adjust IS-IS Timers lab exercise. Click here to start the lab in your browser using GitHub Codespaces (or set up your own lab infrastructure). After starting the lab environment, change the directory to feature/6-timers and execute netlab up. ## Lab: Drain Traffic From an IS-IS Node Before Starting Maintenance DevFeed: [Lab: Drain Traffic From an IS-IS Node Before Starting Maintenance]() Original publisher: [Read original article]() Published: 2025-10-23T05:09:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [networking](), [Routing (disambiguation)](), [Protocol (disambiguation)]() Tags: [browser](), [github](), [infrastructure](), [is-is](), [maintenance](), [netlab](), [protocol](), [routing]() ### AI overview This lab demonstrates how to drain traffic from an IS-IS node before maintenance by using the IS-IS overload bit. The bit signals other routers to stop using the node for transit traffic, allowing routing tables to adjust before traffic is disrupted. ### Source excerpt Here's a cool feature every routing protocol should have: a flag that tells everyone a node is going down, giving them time to adjust their routing tables before disrupting traffic flow. OSPF never had such a feature; common implementations set the cost of all interfaces to a very high value to emulate it. BGP got it (the Graceful BGP Session Shutdown) almost 30 years after it was created. IS-IS had the overload bit from day one, and it's just what an IS-IS router needs to tell everyone else they should stop using it for transit traffic. You can try it out in the Drain Traffic Before Node Maintenance lab exercise. Read more ... ## Lab: Hide Transit Subnets in IS-IS Networks DevFeed: [Lab: Hide Transit Subnets in IS-IS Networks]() Original publisher: [Read original article]() Published: 2025-10-17T05:46:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [Networks](), [IP routing]() Tags: [browser](), [github](), [ipv4](), [ipv6](), [is-is](), [netlab](), [networks](), [ospf]() ### AI overview A lab exercise demonstrates how to configure IS-IS to exclude IPv4 and IPv6 transit-link subnets from router PDUs and network-wide IP routing tables. The lab can be run with a supported device, GitHub Codespaces, or self-managed infrastructure using netlab. ### Source excerpt Sometimes you want to assign IPv4/IPv6 subnets to transit links in your network (for example, to identify interfaces in traceroute outputs), but don't need to have those subnets in the IP routing tables throughout the whole network. Like OSPF, IS-IS has a nerd knob you can use to exclude transit subnets from the router PDUs. Want to check how that feature works with your favorite device? Use the Hide Transit Subnets in IS-IS Networks lab exercise. Read more ... ## Lab: Protect IS-IS Routing Data with MD5 Authentication DevFeed: [Lab: Protect IS-IS Routing Data with MD5 Authentication]() Original publisher: [Read original article]() Published: 2025-09-26T05:40:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [IS-IS](), [networking](), [Authentication](), [BGP]() Tags: [authentication](), [bgp](), [github](), [is-is](), [netlab](), [routing](), [state]() ### AI overview This lab exercise explains how IS-IS authenticates routing traffic using cleartext passwords or MD5 and SHA hashes. It covers authentication for hello packets and Link State PDUs, and directs readers to launch the lab with GitHub Codespaces or their own infrastructure. ### Source excerpt Like OSPF and BGP, IS-IS contains a simple mechanism to authenticate routing traffic - IS-IS packets can include a cleartext password or an MD5- or SHA hash. Unlike OSPF, IS-IS can also authenticate: The hello packets exchanged between routers The contents of Link State PDUs flooded across an area or a domain. Want to know more? Check out the Protect IS-IS Routing Data with MD5 Authentication lab exercise. Click here to start the lab in your browser using GitHub Codespaces (or set up your own lab infrastructure). After starting the lab environment, change the directory to feature/3-md5 and execute netlab up. ## Updated: netlab Network Topology Graphs DevFeed: [Updated: netlab Network Topology Graphs]() Original publisher: [Read original article]() Published: 2025-09-16T05:39:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [Graphs](), [Network](), [IS-IS]() Tags: [article](), [blog](), [graph](), [graphs](), [is-is](), [netlab](), [network](), [project](), [series]() ### AI overview This article introduces a series explaining how to generate graphs from netlab lab topologies. It follows netlab release 25.09, which added graphing enhancements and a new IS-IS graph type, and updates an older topology-graphs article. ### Source excerpt netlab release 25.09 introduced numerous graphing enhancements and a new graph type (IS-IS graphs), so I decided to write a series of blog posts explaining how you can generate graphs from netlab lab topologies. I wrote an intro to netlab topology graphs years ago, and as expected, it was hopelessly outdated, so I started the project with a complete overhaul of that article. [Next page]()