I have a basic question about BGP. Can the same AS number be used by a organization at two different sites to peer with two different ISPs?
The scenario is as per what is shown below:
ASN 1111-a (100.100.100.0/24)---ASN XXX---ASN YYY---ASN 1111-b (184.108.40.206/24)
The AS number is 1111. The organization using it at location A to advertise network 100.100.100.0/24 to the ISP peer. At location B the organization is is using the same ASN to advertise 220.127.116.11/24 to another ISP. There is no peering between the two AS 1111 routers as they are physically separated.
Will this work?
what you say look like possible
you need to advertise separate public ip address blocks out of the two sites.
If you try to advertise something more specific that a /24 you may have problems with summarization of your routes at the ISP level.
So it can work in real world if you have at least two /24 public ip address blocks registered with your AS number
without knowing the details of the remote site routes it is difficult to say what is happening when something goes wrong.
>> The BGP rule that says an AS will not accept routes that have it's own ASN in the route
this can be overriden with the command neigh x.x.x.x allowas-in #times
where x.x.x.x is the ISP neighbor
you can still run an iBGP session between the two sites using the public ip addresses over the ISP links just to get the details of routes on the other site.
This can be useful for Disaster Recovery Strategies.
I would configure in this way in your case
Hope to help