Worth Reading: LLM Prompts for Network Engineers

Tony Mattke put together a long list of recommendations that might help you get more out of your LLM tokens.

Definitely worth reading instead of yelling at the stupid AI.

Compress netlab Lab Topologies with Dot Notation

netlab is using the Python Box library to make the code easier to read¹. When I started the project, I hated the way you fetch values from Python dictionaries with stuff like node['ospf']['area']; Python Box lets you write node.ospf.area. Even better², you can tell Python Box to create intermediate dictionaries as needed. node.ospf.area = 1 will automatically create the node.ospf dictionary.

But wait, there’s more (yes, we’re getting to the topic of today’s blog post): Box lets you use the same dotted notation in YAML files.

On ACLs and AI-Generated Device Configurations

Last Friday, I had a lovely chat with Steinn Bjarnarson and Urs Baumann, resulting in the NetworkAutoMagic episode 11. We couldn’t avoid mentioning netlab, the seven layers of ACL hell (which is still balmy compared to the QoS hell), and the gotchas of AI-generated device configurations.

Fortunately, I don’t have to go into more details; Steinn published extensive notes, and if you don’t feel like listening to us while driving, you can waste time watching us on YouTube.

netlab 26.08: ArcOS, VPP (FD.io), ACLs, and DNS

netlab release 26.08 brings a few humongous additions:

• ArcOS support by @roc-ops
• VPP (FD.io) with FRR or BIRD control plane by @jbemmel
• SONiC containers (also by @roc-ops)
• IPv4/IPv6 access control lists in the routing module by @DanPartelly

But wait, there’s more:

On the Futility of Opening Ansible Issues

Remember the anonymous troll who chided me for writing a rant instead of opening a GitHub issue in the relevant Ansible repository? Well, I decided to be an open-source poster boy when I stumbled upon the next Ansible bug, and ended up feeling like a sweet summer child :(

Content: New Parameter in Multiple something_config Ansible Modules

Last December, I wrote a pretty ranty post explaining how Ansible release 12 broke (some?) network device configuration playbooks. The inevitable anonymous troll (why are they always anonymous?) couldn’t resist asking whether I opened an issue on GitHub. I didn’t (more about that later), but when the solution to that rant was “we’re deprecating using templates in src” parameter, I opened an issue arguing why that’s not a good idea.

Worth Reading: Git Oh-Shit Toolkit

Tony Mattke published a blog post I wish I’d read 10 years ago. His Oh-Shit Toolkit includes several tools one can use after messing up Git branches or commit history.

Definitely worth reading, even if you’ve been working with Git for ages.

netlab 26.07: GRE, Wireguard, Graceful Restart, and Scale-Out Labs

The highlights of netlab release 26.07 include:

• The multiserver plugin by @muddyblack distributes containerlab devices across multiple servers.
• The GRE tunnel plugin supports GRE tunnels on Cisco IOS, FRR, VyOS, and Junos (vSRX and vJunos-router) (most device implementations done by @ssasso and @jbemmel).
• The WireGuard tunnel plugin by @jbemmel supports WireGuard tunnels on FRR.
• The bgp.session plugin and the OSPF module support graceful restart on Arista EOS, BIRD, FortiOS, and FRR (by @jbemmel and @a-v-popov)
• The bgp.policy plugin supports the bgp.role attribute on FRR and BIRD (by @jbemmel).

But wait, there’s more ;)

netlab: 2000 Pull Requests Later ;))

Jeroen van Bemmel noticed an interesting fact yesterday evening: the netlab GitHub repository has 2000 merged/closed pull requests. I never expected the tiny “let’s learn Python while working around the complexities of Vagrantfile” project to get this far ;))

Thanks a million to everyone who contributed, reported a bug, asked a question, or helped us spread the word. You rock 🤗

Worth Reading: Scripting Good Practices in Python

Just in case you decide to build a simple Python project over the summer: read scripting good practices in Python by Brett Cannon and tell your AI friend to adhere to them ;)

Worth Reading: More VXLAN and EVPN Labs

Ali Bahadır Coşkun continued his EVPN/VXLAN journey. Using the free netlab-powered EVPN/VXLAN labs, he finished the basic EVPN/VXLAN lab (adding EVPN control plane to VXLAN underlay), and then completed the whole VXLAN/IRB/anycast saga.

Want to do something similar? The free EVPN/VXLAN lab exercises include six VXLAN labs, almost a dozen EVPN labs, and a few EVPN designs. I might add a lab or two during the summer break.

Worth Checking: EVPN Centralized Anycast Gateway

Daniel Blažek couldn’t resist testing Arista EOS centralized anycast gateway functionality (on top of IPv6 underlay to make it even more fun) and published working device configurations in a GitHub repo.

His repository includes a containerlab topology definition, so you can start the lab directly from the repository.

Getting Started with netlab @ Cisco DevNet

Cisco DevNet channel has published an hour-long Getting Started with netlab interview with Suresh Vina, resulting in netlab.tools documentation having more weekly visits than ipspace.net blog for the first time. Thanks a million ;))

If you’re new to netlab, I hope you’ll enjoy the video. If you have any follow-up questions, don’t hesitate to start a discussion.

Time for Another Summer Break?

I can confirm that an old saying is true: the older you are, the faster years pass. Can’t believe it’s time for another summer break. I hope you’ll manage to get away from work, turn off the Internet, and enjoy a few days in your favorite spot with your loved ones!

I also promise I won’t be annoying you with boring stuff like EVPN next hops or pointers to AI myth-busters (I have to admit it: I was cleaning my Inbox this week). However, I probably won’t be able to resist publishing a few lightweight netlab-related blog posts, or links to interesting content.

Worth Reading: Appearing Productive in The Workplace

The Appearing Productive in The Workplace article I stumbled upon is yet another masterful description of how AI slop, used by Expert Beginners, wastes everyone’s time and energy. Try to have fun reading it, even though it may be way too close to the mark.

Anycast-Only Gateways in EVPN Asymmetric IRB

In the previous blog post, I described how ARP works in an EVPN asymmetric IRB environment where the PE devices share an anycast MAC/IP address in addition to a unicast MAC/IP address. Today, let’s see how well things work if the PE devices have only the anycast MAC/IP address:

Worth Reading: My Network is Talking Back Thanks to SuzieQ MCP

Claudia de Luna published a step-by-step description of how you can use SuzieQ data with an AI agent.

That’s definitely interesting, but I found the list of MCP resources at the end of her blog post even more valuable; that’s a keeper even if you never looked at SuzieQ (in which case you REALLY SHOULD).

Worth Reading: AI Enthusiasts Against AI Skeptics

Charity Majors wrote an excellent article describing AI enthusiasts in a race against time and AI skeptics in a race against entropy. Fair warning: its very first sentence triggered an acute case of PTSD:

I recently attended a talk where one of the presenters made some pretty…astonishing claims about what they had achieved by the pure, uncut power of vibe coding.

I’ve seen way too many presentations making “astonishing claims” about the unlimited unicorn-driven powers of OpenFlow, SDN, OpenDaylight, or Ansible.

Worth Reading: Extending a VLAN with Static VXLAN

Ali Bahadır Coşkun wrote a nice article describing how he mastered extending a VLAN with static VXLAN with the help of free netlab-powered VXLAN labs.

The same set of lab exercises includes six VXLAN labs, almost a dozen EVPN labs, and a few EVPN designs. I might add a lab or two during the summer break.

ARP with Anycast Gateways in EVPN Asymmetric IRB

In previous blog posts, I described the ARP issues in EVPN environments, starting with centralized routing, and then asymmetric IRB with unicast (per-leaf-switch) first-hop gateways. Of course, no self-respecting vendor would tell you to do that; anycast gateways are all the rage these days.

As always, anycast gateways could mean different things, depending on which vendor documentation you read ;)

1. Active-active VRRP (one device is the active VRRP gateway, but all devices listen to the VRRP MAC address).
2. Shared MAC+IP address beside device-specific unicast MAC and IP addresses.
3. Shared MAC+IP address with no PE-specific IP address.