2 BGP Multi-homed Sites, single AS number

Undy

Hi Folks. I have a single site which is multi-homed with ISP 1 and ISP 2 accepting a default route and advertising a class C. I have a second site that does not connect to site 1. I would like to do the same setup, multi-home to two ISP's and advertise a different class C. ARIN is giving me a hard time asking why I need a second AS. I think I just assumed that I would need another AS, but I am starting to think that I don't. Is there any reason I wouldn't be able to use the same AS in two different sites advertising two different networks?

The only thing I can think of is: One ISP at both sites would be the same. If I was to receive a partial about either site, the route from the other site would be sent containing the same AS number. It would then be rejected since the AS Path would look like a loop since it's own AS would be in the path attribute.

Has anyone done this before?

Thanks!

pham0329

That should be OK, as long as you dont ask the ISP to advertise the specific route to the other site, and vice versa.

DPG

You only need 1 AS. Just make sure you configure allowas-in if you plan on taking more than a default route at each site.

Undy

Thanks DPG. I was just reading about that as you posted. That will work perfect.