Fact number one: I wanted to write a small note about SRv6. Not even about SRv6 as a protocol, really, but about the road the industry travelled from plain old LDP to a world where an IPv6 address can be both a destination and an instruction.

Disclaimer #1

Before going any further, open Two Labels, One SRH, and One Very Annoying rp_filter and skim it for five minutes. That article is the polished technical result I originally wanted.

Spoiler: this is not about stuffing more words like mpls, segment-routing, and srv6 into a config. It is about stopping after every one of those words and asking: where did the packet actually go?

We had ten Linux machines connected by virtual links, plus a separate management network. At the beginning, this was not an “MPLS lab”: there was no IPv4 data plane, FRR was missing on some nodes, and the neighbors shared little more than interfaces and a healthy amount of mutual suspicion.

From a network engineer to network engineers. No bullshit.

The Lab Setup

Alright, folks. We’re about to simulate a “baremetal” Kubernetes cluster. And by “baremetal,” I of course mean an Ubuntu VM running inside a hypervisor that’s itself virtualized. You get the idea. Here’s the master plan:

Now, because we’re doing this the right way:

1. We’ll emulate the whole thing right in PNETLAB.

2. We’re using a Leaf-Spine topology. Standard.