Duplicating BGP AS numbers

[pingboy]

We have multiple sites (approx 900 sites) that need to be connected to ISP via BGP connection. We are thinking of duplicating the private AS in few sites so that we will not run short of private AS in future. How do I achieve this and what configuration will suit most ? (example : ISP AS - 13979, Ours - 65000,64200 etc)

Thank You in advance.

 

[dgrizzard]

You can setup the private-as to be whatever you want, each could have an AS of 65000 because sites won't be peering to each other.


They're not right?

 

[pingboy]

Nikeair,

The sites should be peering with the Data Centres that located in 3 different region. Some small sites might be peering with each other in the same location.

 

[Quadratic]

Are these BGP neighborships strictly for Internet access from your branch offices, where conventional VPNs are set up for site-to-site connectivity, or are these neighborships part of an MPLS VPN solution with your ISP? Do the branch sites need to relay traffic between each other via the data centers? How are the BGP neighborships between branch site and data center being established? Is a diagram of the proposed setup available to help illustrate this?

CCNP, CCDP, CCIP
Core Network Planner, ISP

 

[pingboy]

This BGP neigbourships are connected via MPLS solution. The branches will only relay traffic between DC's. At the moment each BGP speakers are assigned with unique Private AS but we feel we'll run out of Private AS soon. That is the reason we plan to duplicate the Private AS at few locations to reserve for future use.

 

[Jaspair]

A site with the same AS-number as the advertised route will not accept this route because of loop prevention.

If sites with the same AS-number needs to communicate with each other you can ask the provider to do AS-override.

See this link for more information:

http://fengnet.com/book/MPLS Configuration on Cisco IOS Software/ch06lev1sec1.html

If the sites only needs to communicate with the DC's you only have to make sure the sites have other AS-numbers than the DC's

 

[Quadratic]

I should caution that AS Override has the potential for creating routing loops, especially if you have any connections between branch offices other than via the MPLS VPN. There may be other options as well if the provider has any issues with provisioning AS Override, though with so many branch offices I'm guessing you're an important enough customer for them to make that leap for you.

CCNP, CCDP, CCIP
Core Network Planner, ISP

 

[pingboy]

Thank you guys for the valuable information