Blog Posts in November 2024
Lab: Using IS-IS Metrics
It’s time for another “the vendor IS-IS defaults are all wrong” blog post. Wide IS-IS metrics were standardized in RFC 3784 in June 2004, yet most vendors still use the ancient narrow metrics as the default setting.
Want to know more? The Using IS-IS Metrics lab exercise provides all the gory details.
Latency Numbers Every Programmer Should Know
One of the key arguments against stretched clusters (and similar stupidities) I used in my Disaster Recovery Myths presentation was the SSD read latency versus cross-site round-trip time.
Thanks to Networking Notes, I found a great infographic I can use in my next presentation (bonus points: it also works great in a terminal when fetched with curl) and a site that checks the latency of your web site from various vantage points.
Using a BGP Route Server in an Internet Exchange Point
A BGP route server is like a BGP route reflector but for EBGP sessions. In its simplest implementation, it receives BGP updates over EBGP sessions and propagates them over other EBGP sessions without inserting its own AS number in the AS path (more details).
BGP route servers are commonly used on Internet Exchange Points (IXPs), and that’s what you can practice in the BGP Route Server in an Internet Exchange Point 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 session/5-routeserver and execute netlab up.
Running Routing Protocols over Tunnels
James got confused by a statement made by Hannes Gredler in his IS-IS book:
Things behave really badly if the total IGP cost over the tunnel undermines the total topologies’ cost. What happens next is that the tunnel “wraps” around itself, ultimately causing a meltdown of the entire network.
Let’s unpack that, starting with “Why would you need a tunnel?”
netlab 1.9.2: STP, LAG, Cisco IOL, Edgeshark
While I was busy fixing bugs in the netlab release 1.9.2, other contributors added exciting new features:
- Jeroen van Bemmel added the spanning tree and link aggregation configuration modules, initially implemented on Arista EOS, Cumulus Linux, and FRR.
- Dan Partelly added the netlab exec command that can execute the same command on a set of network devices, support for Edgeshark, and support for Cisco IOS on Linux (IOL) and Cisco IOS layer-2 image on Linux (IOLL2), the latter after a heroic uphill battle with ancient software (part 1, part 2).
Other new features include: