07-17-2021 12:46 PM
hi Team
I have some questions about BGP if you please :
1- if we have in our environment BGP domain one cluster for two RR, and as we know RR once receive a packet will generate two attributes to prevent loop ( originator and cluster list ) so now what is the difference between both of them ( if we are in the same domain ) and there is only one cluster,
2- what is the difference between ( max-path, multiple iBGP sessions on the RR. and add-path)
3- is there any article explain the problem we may face using RR or confederations we can understand these technical deeper
Solved! Go to Solution.
07-18-2021 09:48 AM
Hello @mautez_mah ,
I was referring to the case where the route reflector client reiceves the best path via two different RRS, in this case the route propagated by the RRS with the lowest BGP RID is preferred and selected as best
And even if it is not reported in the best path BGP selection in Cisco documents the Cluster List attribute is used to select the best path.
Hope to help
Giuseppe
07-17-2021 03:31 PM - edited 07-17-2021 03:33 PM
07-18-2021 05:29 AM - edited 07-18-2021 05:31 AM
Hello @mautez_mah ,
when you use two RR servers serving the same set of clients you have two design choices:
1) use the same cluster-id on both
2) use a different cluster-id on the two RRS
The second choice will generate more reflected advertisements as the two RRS will see each other as not being in the same "cluster".
However, this second choice allows to cover some fault cases that choice 1) is not able to cover: if there are two clients X and Y with X having lost the iBGP session with RRS2 and Y having lost the iBGP session with RRS1 the exchange of routes between X and Y still happens going via the two RRS because of the different cluster-id.
About your other questions:
Both RRS will choice the same best path so each client will select as best path the one coming from the device with lowest BGP RID.
Hope to help
Giuseppe
07-18-2021 07:07 AM
@Giuseppe Larosa many thanks
just can u explain more plz "Both RRS will choose the same best path so each client will select as the best path the one coming from the device with the lowest BGP RID. I know each client will install the best route from RR ,
07-18-2021 09:48 AM
Hello @mautez_mah ,
I was referring to the case where the route reflector client reiceves the best path via two different RRS, in this case the route propagated by the RRS with the lowest BGP RID is preferred and selected as best
And even if it is not reported in the best path BGP selection in Cisco documents the Cluster List attribute is used to select the best path.
Hope to help
Giuseppe
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