[c-nsp] IOS-XR BGP RR MCID (Multiple Cluster ID)

[adamv0025 at netconsultings.com]

Cluster-ID saves RAM only if RR1 and RR2 are connected like in your case, if they are not and RR1s only talk to RR1 in other POPs and RR2s only talk to RR2s in other POPs/Clusters then the Cluster-ID is just for loop prevention really. 

 

And on a side note, 

Although Cluster-ID saves some RAM in case RR1 and RR2 are connected and configured with the same Cluster-ID –it doesn’t save CPU cycles (and RAM necessary for particular RIB out/RIB in) where RR1 sends couple Mill of prefixes to RR2 only for RR2 to drop all of those (well apart form couple of the odd prefixes originated by RR1) and vice versa in the opposite direction. 

 

adam

 

netconsultings.com

::carrier-class solutions for the telecommunications industry::

 

From: Mark Tinka [mailto:mark.tinka at seacom.mu] 
Sent: Monday, March 12, 2018 2:52 PM
To: adamv0025 at netconsultings.com; 'Saku Ytti'
Cc: 'Job Snijders'; 'Cisco Network Service Providers'
Subject: Re: [c-nsp] IOS-XR BGP RR MCID (Multiple Cluster ID)

 

 

On 12/Mar/18 16:19, adamv0025 at netconsultings.com <mailto:adamv0025 at netconsultings.com>  wrote:

In iBGP infrastructures I used or built the use of common/unique cluster IDs is not saving any memory and is used solely for preventing a RR to learn its own advertisements from the network.  


That saves RAM, otherwise with unique Cluster-ID's, RR's in will exchange client routes with each other, using up RAM.

But this only applies to client routes. Routes originated by the RR are learned by neighbor RR's in a shared Cluster-ID scenario, which is useful.

Mark.