I’m too old to be fighting with windmills, but sometimes I have to get a rant off my chest. This one was triggered by the latest episode of the hilarious¹ “DHCPv6 on Android” soap opera

In a 720-degree turnaround, Android 11 supports DHCPv6, but only for prefix delegation purposes. Yes, you got it right, in a year or two, every phone might want to have a dedicated /64 prefix assigned to it on WiFi segments².

Want more details? Well, there’s a high-level overview published on the Android Developers blog and a corresponding message sent to the v6ops mailing list. Let’s see how much sense that makes.

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.

Someone approached me after my NOG.HR netlab presentation and said: “wouldn’t it be great if we could just start the lab from an example topology published on GitHub?”

It took me almost a year to get it done, but the functionality finally made it into the 25.09 release:

Is it possible to deploy Precision Time Protocol across a country-wide WAN network and reach nanosecond-level synchronization between cities? It’s definitely not trivial and only works over dedicated infrastructure; for more details, watch the PTP in WANs (video) presentation Oliver Ettlin had at SwiNOG 40.

Last week, I explained how to generate network topology graphs (using GraphViz or D2 graphing engines) from a netlab lab topology. Let’s see how we can make them look nicer (or at least more informative). We’ll work with a simple leaf-and-spine topology with four nodes¹:

defaults.device: frr
provider: clab

nodes: [ s1, s2, l1, l2 ]
links: [ s1-l1, s1-l2, s2-l1, s2-l2 ]

This is the graph generated by netlab create followed by dot graph.dot -T png -o graph.png:

When I was writing a blog post, I needed a link to the netlab lab topology documentation, so I searched for “netlab lab topology” (I know I’m lazy, but it felt quicker than navigating the sidebar menu).

The AI overview I got was way too verbose, but it nailed the Key Concepts and How It Works well enough that I could just use them in the netlab README.md file. Maybe this AI thing is becoming useful after all ;)

I wrote about the optimal BGP path selection with BGP additional paths in 2021, and I probably mentioned (in one of the 360 BGP-related blog posts) that you need it to implement IBGP load balancing in networks using BGP route reflectors. If you want to try that out, check out the IBGP Load Balancing with BGP Additional Paths 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 lb/4-ibgp-add-path and execute netlab up.

I always ask engineers reporting a netlab bug to provide a minimal lab topology that would reproduce the error, sometimes resulting in “interesting” side effects. For example, I was trying to debug a BGP-related Arista EOS issue using a netlab topology similar to this one:

defaults.device: eos
module: [ bgp ]
nodes:
  a: { bgp.as: 65000 }
  b: { bgp.as: 65001 }

Imagine my astonishment when the two switches failed to configure BGP. Here’s the error message I got when running the netlab’s deploy device configurations Ansible playbook:

During integration testing, I find unexpected quirks in network devices way too often. However, that’s infinitely better than experiencing them in production (even after thoroughly testing stuff) while discovering that your peers don’t care about routing security, RPKI, and similar useless stuff.

For example, what happens if you define a new Routing Control Function (RFC) on Arista EOS and apply it to BGP routing updates in the same configuration session? You’ll find out in the Sorry We Messed Up (video) presentation Stefan Funke had at SwiNOG 40 (note: the bug has been fixed in the meantime).

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.