02-22-2004 08:42 AM - edited 03-02-2019 01:46 PM
I have have a setup where BGP with AS "X" has received a route from AS "Y". I have to ways between AS "Y" and "X" . How do I get AS "X" to advertise this route back to AS "Y" when it has originated from "y"?
I hope you can help, thanks.
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02-22-2004 09:14 AM
The BGP loop detection takes place when the eBGP updates are received. So in your scenario, AS X will advertise the prefixes to Y even if the AS-PATH contains Y. AS Y would then see its own ASN in the AS-PATH and reject the prefix. Assuming that AS Y is discontiguous, you can use the following command to accept the prefixes even if the local AS number is part of the AS-PATH received from AS X:
neighbor x.x.x.x allowas-in
This would have the effect of using AS X as a transit AS between the disconguous parts of AS Y.
Care should be taken when using this command as it bypasses the regular BGP loop detection.
Hope this helps,
02-22-2004 09:14 AM
The BGP loop detection takes place when the eBGP updates are received. So in your scenario, AS X will advertise the prefixes to Y even if the AS-PATH contains Y. AS Y would then see its own ASN in the AS-PATH and reject the prefix. Assuming that AS Y is discontiguous, you can use the following command to accept the prefixes even if the local AS number is part of the AS-PATH received from AS X:
neighbor x.x.x.x allowas-in
This would have the effect of using AS X as a transit AS between the disconguous parts of AS Y.
Care should be taken when using this command as it bypasses the regular BGP loop detection.
Hope this helps,
02-23-2004 03:59 AM
Hi hritter
It was exactly this command that I needed. Everything works the way I want to now.
Thank you very much for your time and help.
Best regards,
Jesper
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