2 BGP Multi-homed Sites, single AS number

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!

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Comments

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.