Routing

Hello Experts

How originator ID is useful for loop prevention in RR topology. As I understand cluster ID is used for loop prevention but I dont know the role of originator ID?

The originator ID makes sure the BGP updates is not looped back to the BGP router it once sent if this router is client of multiple route reflector, e.g.

R1  --- RR1 (cluster ID: 1.1.1.1) --- RR2 (cluster ID: 2.2.2.2) --- R1

Therefore, the first route reflector adds the originator ID to the BGP attributes.

Cheers,

Carsten

Thank you

Hello,

Originator ID is also used in BGP Path selection - otherwise, when comparing reflected routes, Path selection code would compare RR' router-id with itself, which defeats the purpose of "lowest router-id" tie-breaking 

Prefer the path from the peer with the lowest router ID. For any path with an originator ID attribute, substitute the originator ID for the router ID during router ID comparison.

http://www.juniper.net/documentation/en_US/junos12.1/topics/reference/general/routing-ptotocols-address-representation.html

HTH

Thanks

Alex

Hi Alex

Sorry for my ignorance. Can you please explain it further. As I understand RR does not change any thing when doing the reflection. 

Hello,

Any reflected route will appear as coming from "Router-ID"==RR router-id.

Hence, to make "lowest router-id" path selection step to work for a given specific route coming from multiple RR clients, originator-id must be compared instead.

HTH

Thanks

Alex

Thank you. I was thinking protocol nexthop is equal to router-id