VRF Route Distinguisher

[julianov403]

Hello all. I hope you are doing well. 

Trying to configure a VRF I've success on it but there is one little code that I dont understand. 

ip vrf NAME 
rd 1:7 
route-target export 1:7 
route-target import 1:7

the rd value its 1:7. The first number (1) is a random value? because the "TAG" is 7, right? 

Thanks in advance. 

[Francesco Molino]

Hi

Rd and rt isn't mandatory that they have same value.
Here rfc explaining rd : https://tools.ietf.org/html/rfc4364#section-4.2

There's no random value in rd value. There's no rules but as best practices we define it by using the following format: ASN:SiteID
You can also use the format IP-ADDRESS:NN, this will help by identifying the originating router.

[julianov403]

Thanks for the reply.

Regarding ASN it says that It must be an autonomus number. what does it means?

Regarding SiteID I think it is the number to distinguis the VPN. that is correct?

[Francesco Molino · Accepted solution]

As I said, you can have the 1st part to be the ASN or the IP of the router and SiteID will be an ID you define for each of your sites, then the BGP update would like like:
ASN:ID:subnet or IP_RTR:ID:subnet, the combination of all those values is what will make this subnet unique in the BGP table and will allow you to know from where the advertisement is coming.

Is it clear?