0

I know the explanation about the usage of RD, that it makes routes from different VRFs globally unique. AFAIK, a VPN route is composed of [RD] + [VPN label] + [Prefix] Isn't the VPN label, that is allocated for each VRF anyway, enough to make the route globally unique? Isn't [VPN label] + [prefix] unique enough?

Is RD used because it's user configurable and allows for more control? unlike VPN labels that are randomly allocated by the router.

Or maybe RD is used - since a VPN label isn't always mapped directly to a VRF (maybe sometimes it's mapped to a route directly, to save a VRF IP lookup when forwarding traffic towards a CE router)

Improve this question
1

AFAIK, a VPN route is composed of [RD] + [VPN label] + [Prefix]

That's not correct. A route is RD + prefix.

Remember packets have labels -- routes have distinguishers

An MPLS VPN is a bit abstract. It's a collection of VRFs that share a common route policy.

Improve this answer
7
  • so is it possible that two or more VRFs are represented by a single a label? (Should they have the same RD in that case?)
    – manish ma
    Jun 11 at 7:18
  • You are confusing two separate things. Labels do not define VPNs
    – Ron Trunk
    Jun 11 at 12:14
  • So what do VPN labels define then?
    – manish ma
    Jun 11 at 13:34
  • They define the flow from the ingress LSR to the egress LSR.
    – Ron Trunk
    Jun 11 at 14:07
  • There are two labels, I'm talking about the inner label that represents the VRF
    – manish ma
    Jun 11 at 16:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.