Pros & Cons for having multiple AS for the same VRF

[ccie16351]

Hi,

I just wonder if there is any added value of having mutiple private AS numbers for a single VRF, compared to the usual practise of having one single AS for the entire enterprise network of a give customer. The solution provider is setting a requirement for having 3 AS numbers to connect to the MPLS IP-VPN, one AS for Primary Data Center, and one for Disaster Recovery Center and one for all the 1,000+ branaches.

Appreciate your input.

Sam

[Mahesh Gohil · Accepted solution]

Hi,

I don't see any benefit for using three different AS number. Only benefit is we need not to use as-override (or allowas-in)

if having three different AS.

I worked for on Provider who was not much strong in processes and was not having automated tool to configure customer links, i mean everything was manual. I see many times that though customer requested to use as-ovveride at provider link

people generally forget to configure the same and at time of testing the usual fault was missing this command at provider end.

But if your provider is standard ( in terms of processes) then You can use only one AS number. This is what i experienced. technically i dont see much benefit in having three different AS.

Regards # Mahesh

[ccie16351]

Hi Mahesh,

an idea just crossed my mind, another benefit beside ignoring "as-override" at the PE, the custmer would be able to set "as-path access-list" at their CEs to allow-in only their own AS numbers, like at the branch they can allow the AS of Primary Data Center and the DRC.

Anyway, thank you for your input.

Sam