Moving toward single global VLAN namespace

[ipspace]

In theory, the current implementation of the VLAN module supports node-specific VLANs with the same name. For example, multiple nodes might have a red VLAN, but as long as it's not defined globally, these are not the same VLANs and will get different VLAN IDs (at least that's how I remember the code behaving 🥴).

It would make everyone's life easier if we'd go for globally unique VLAN namespace, disallowing having the same VLAN name on multiple nodes without having a global VLAN with the same name (or creating global VLAN on the fly). Obviously you could still use red_s1, red_s2, red_s3 if you wish.

Please note that this change would not impact routed VLANs used in stuff like VRF Lite. Those VLANs always get an IP prefix per physical link.

So: is anyone using node-specific VLANs @jbemmel @ssasso @petercrocker?

[ssasso]

I have some use cases where I want to use the same vlan id on different links (but not the same vlan "globally speaking") - but never tested yet with netlab, even if it's in my todo list.
So, even if using a global vlan namespace, this should allow "overlapping" IDs...

So, if I can have

vlans:
  s1_red:
    id: 10
  s2_red:
    id: 10

for me it's ok.

[ipspace]

Oh, that wouldn't work. I think we check for unique IDs. But there's nothing enforcing VLAN continuity, so it's perfectly OK to have a bit of VLAN 10 here, another bit of VLAN 10 over there... as long as you're OK with VLAN 10 having the same IP prefix everywhere.

[jbemmel]

Netlab ties all ports with a given VLAN ID together into a single L2 domain. Building a model with 'port significant' vlans would only be possible using a plug-in

[ipspace]

@jbemmel fixed #287 -- this discussion is moot