Can you have multiple BGP AS 's running simultaneously on a 3560?

[Thomas Cotton]

Hi,

I have a customer who's currently running one BGP AS between their core 3560 stack and their existing ISP routers, this handles the advertisement and availability of the main site, and should this stop advertising traffic would be sent to the backup site.

They're in the process of moving to another ISP and the plan was to create a second BGP AS for the new ISP so the above mentioned solution wasn't affected, however when the customer type router bgp ***** the command will not take, is this because the 3560 only supports a single BGP AS?

Cheers

[vivek srivastava · Accepted solution]

Hi Thomos,

Every device only supports single bgp session i.e. "router bgp xx" you can't use second session i.e. "router bgp yy" on the same device.

Now in your case since you need to migrate to other ISP with different BGP ASN and keep existing BGP ASN as well, you need to go for below config:

router bgp 100

neighbor e.f.g.h remote-as 300

neighbor a.b.c.d remote-as 200
neighbor a.b.c.d local-as 101

In this way you can have your current AS(100) for current ISP(300) and can make BGP session with 2nd ISP(200) with your new ASN(101).

For details, refer below link:

http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13761-39.html
 

Vivek

[Thomas Cotton]

Thanks Vivek, much appreciated