ipSpace.net blog

I work on a laptop that loves to power down when not used (the right thing to do), which often breaks the SSH session to my netlab server (not so good).

Most vendors “discovered” anycast gateways when they tried implementing routing between MAC-VRFs in an EVPN environment and hit all the usual tripwires (more about that later).

Something didn’t feel right as I tried to check whether the IPv4 ECMP I observed in the latest version of Arista cEOS containers works with my MPLS/anycast scenario.

When I started the Online BGP Labs project in mid-2023, Cumulus Linux still seemed like a good platform to use.

In October 2023, I was talking about Internet routing security at the DEEP conference in Zadar, Croatia.

A netlab user wanted to create a nice-looking topology graph from a simple topology connecting a few devices to a broadcast (multi-access) link.

Whenever I’m ranting about vendors changing their data models or APIs with every other release, there is inevitably a vendor engineer chiming in, saying, “Life would be so much better if the customers wouldn’t insist on doing screen scraping for the last…

When I wrote about the anycast-ECMP-in-MPLS behavior in 2011, I had to use Cisco IOS to prove that ECMP worked, since Arista cEOS (running the Linux kernel for IP forwarding) didn’t install more than one equal-cost path into the Linux forwarding table.

Here’s an interesting tidbit from the what took them so long department: Cloudflare One Client continuously measures end-to-end MTU and adjusts the local tunnel interface MTU size accordingly (warning: there’s a fair amount of dubious handwaving over the…

netlab release 26.03 is out.

We haven’t implemented support for Cisco SD-WAN in netlab yet, and we might never do so; after all, netlab isn’t meant to be a kitchen sink of vendor-specific features.

Yesterday, I had a short presentation on netlab use cases during the NetBCN event.

I decided it was high time to create EVPN/MPLS netlab integration tests and wanted to use the same approach I used for the EVPN/VXLAN ones: One of the PE-devices is the device we want to test The other PE-device is a device that is known to work (ideally,…

Bruce Davie published a nice article explaining why it makes little sense to use an algorithm that’s supposedly faster than Dijkstra’s in link-state routing protocols.

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.

In the first EVPN/VXLAN lab, we added the EVPN control plane to bridging over VXLAN.

Imagine you want to deploy a BGP route reflector for MPLS 6PE or L3VPN service.

I guess your LinkedIn feed is as full of AI nonsense as mine is, so I usually just skip all that posturing.

Following a link in another Martin Fowler’s blog post, I stumbled upon his thoughts on Open Space events – a way to set up self-organizing events.

Petr Ankudinov wrote an excellent comment about netlab Fast cEOS Configuration implementation.

What’s wrong with me?

Last week, I described some of the gotchas I encountered while trying to make EVPN MAC-VRFs work on Cisco IOS/XE.

Ignoring the obligatory misguided mention of OpenFlow and a few other unicorns, I found this article to be a nice introduction to modern forwarding architectures, including networking infrastructure for AI clusters and distributed cell-based fabrics.

Apart from IP multicast and QoS, netlab can configure commonly used networking technologies across dozens of devices from most networking vendors.

Want to spend an hour or two configuring some cool stuff this weekend?

After reading the L2 Vxlan On Catalyst blog post, I decided to add EVPN configuration templates to netlab-supported Cisco IOS/XE devices.

netlab release 26.02 is out, including the usual potpourri of goodies: Support for Kubernetes (KinD) clusters based on work by @wnagele Layer-2 EVPN/VXLAN support on Cat8000v, IOL, and IOLL2 netlab graph command can create graphs from a subset of nodes or…

Brian Linkletter published an updated overview of open-source network simulators and emulators. containerlab and GNS3 are clear leaders (no surprise there) with the original vrnetlab becoming abandonware (fortunately, we have Roman Dodin’s fork), which ma…

After the enormous speedup I achieved with the FRR containers, I tried to do something similar with the Arista cEOS ones.

In the previous EVPN/VXLAN lab exercises, we covered the basics of Ethernet bridging over VXLAN and the use of the EVPN control plane to build layer-2 segments.

Whenever I claim that the initial use case for MPLS was improved forwarding performance (using the RFC that matches the IETF MPLS BoF slides as supporting evidence), someone inevitably comes up with a source claiming something along these lines: The idea…

In 2017 (over eight years ago), I was making fun of the fact that “VXLAN is insecure” was news to some people.

Here’s another “You can’t make this up, but it sounds too crazy to be true” story: Cisco IOS layer-2 images change the interface MAC address when you change the interface switchport status.

After creating the infrastructure that generates the device configuration files within netlab (not in an Ansible playbook), it was time to try to apply it to something else, not just Linux containers.

A friend of mine sent me a series of questions that might also be on your mind (unless you’re lucky enough to live under a rock or on a different planet): I wanted to ask you how you think AI will affect networking jobs.

There’s no “networking in 20xx” video this year, so this insightful article by Anil Dash will have to do ;) He seems to be based in Silicon Valley, so keep in mind the Three IT Geographies, but one cannot beat advice like this: So much opportunity, inspir…

In the previous VXLAN labs, we covered the basics of Ethernet bridging over VXLAN and a more complex scenario with multiple VLANs.

Imagine you want to use netlab to build training labs, like the free BGP labs I created.

If you’re at all interested in the history of networking, you simply MUST watch the BGP at 18: Lessons In Protocol Design lecture by Dr.

Petr Ankudinov made an interesting remark when I complained about how much time I wasted waiting for Cisco 8000v to boot when developing netlab device configuration templates: For Arista part - just use AVD with all templates included and ANTA for testing.

One of the major differences between OSPF and IS-IS is their handling of inter-area routes.

One of my readers attempted to implement a multi-vendor multicast VPN over MPLS but failed.

TL&DR: Of course, the title is clickbait.

Why do we need Infrahub, another network automation tool?

David Gee was time-pressed to set up a demo network to showcase his network automation solution and found that a Ubuntu VM running netlab to orchestrate Arista cEOS containers on his Apple Silicon laptop was exactly what he needed.

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]

I completely rewrote netlab’s device configuration file generation during the New Year break. netlab Release 26.01 no longer uses Ansible Jinja2 functionality and works with Ansible releases 12/13, which are used solely for configuration deployment.

They say time goes faster as you get older, and it seems to be true.

Want to look up various HTTP status/error codes when troubleshooting a DNS BGP network server problem?

A month ago, I described how Ansible release 12 broke the network device configuration modules, the little engines (that could) that brought us from the dark days of copy-and-paste into the more-survivable land of configuration templates.