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BGP and same ASN number

prashantrecon
Beginner
Beginner

Hi Team,

I have a doubt , I want to use same ASN number at different sites with different- different ISP.(consider i have public ip range 1.1.1.0/24 )

consider I have a public server with ip 1.1.1.1 at site A and and if i advertise same Public pool at B site , how return traffic know that if it has to come at site A or B.

or if some one from Internet want to access this 1.1.1.1 public server , Is that request will come to on Site A router or Site B router . 

Regards,

Prashant

19 REPLIES 19

Hello

Maybe I could have been a wee bit clearer on what I was trying to say.

Duplicate ASN isn't really applicable between two sites exchanging routes due to Bgp default loop mechanism that an "AS will not accept routes that have it's own ASN in the route"

Now given you have two separate sites but one public ASN - My understanding is the ISPs will usually summarises prefixes and it's this summarisation which could possibly cause issues when two separate sites are using the same ASN.

So wouldn't it be more applicable use a private ASN and let your local ISP filter on this number prior to advertising your routes Into the public domain.

Res
Paul


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Kind Regards
Paul

Since this appears to be Provider Independent address space, I wouldn't think the ISP at each end would be able to summarize these networks???

With PI space they would not be able to summarize.

I was assuming that hosts at site1 won't need to reach hosts at site2 unless they have an additional range used for communicating between each other.

Daniel Dib
CCIE #37149

Please rate helpful posts.

Daniel Dib
CCIE #37149
CCDE #20160011

Please rate helpful posts.

Makes sense.

Thanks Daniel

Sites 1 won't need to reach host at sites 2.(They don't need to communicating with each other)

Sites 2 only need/came up when site1 goes Down .

Regards,

Prashant

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