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Aninda Chatterjee#

  • 24 min read

Asymmetric routing with SR Linux in EVPN VXLAN fabrics

This post dives deeper into the asymmetric routing model1 for EVPN VXLAN fabrics on SR Linux.
The topology in use is a 3-stage Clos fabric with BGP EVPN and VXLAN, with

  • server s1 single-homed to leaf1
  • s2 dual-homed to leaf2 and leaf3
  • and s3 single-homed to leaf4.

Servers s1 and s2 are in the same subnet, 172.16.10.0/24 while s3 is in a different subnet, 172.16.20.0/24. Thus, this post demonstrates Layer 2 extension over a routed fabric as well as how Layer 3 services are deployed over the same fabric, with an asymmetric routing model.

The physical topology is shown below:

  • 23 min read

SR Linux (aka SRL), released back in 2021, is a new operating system from Nokia, designed to power data center fabrics, with network automation no longer being treated as a second-class citizen. SR Linux is built from the ground up using YANG, which is a modeling language describing how data is structured. As an operator, this enables you to view the entire structure as a schema tree (which we will see shortly).

Like any new operating system, there is a learning curve. In the past, I have had to learn several new operating systems (having originally started with Cisco IOS), including Cisco IOS-XE/NXOS, Arista EOS, Cumulus NCLU/NVUE, Juniper Junos and now, Nokia SR Linux. In general, I have always followed the same methodology in learning - learn by building something relatable. Since SR Linux focuses on data center fabrics, we're going to build something a little relatable to that. Let's dive in.

This is a condensed version of a larger SR Linux Getting Started Guide.