Best practices for BGP Communities

Tue Mar 5 23:32:07 UTC 2019

On 3/5/19, 6:04 PM, "NANOG on behalf of Job Snijders" <nanog-bounces+courtney_smith=comcast.com at nanog.org on behalf of job at instituut.net> wrote:

    On Sun, Mar 03, 2019 at 08:42:02PM -0500, Joshua Miller wrote:
    > A while back I read somewhere that transit providers shouldn't delete
    > communities unless the communities have a specific impact to their
    > network, but my google-fu is failing me and I can't find any sources.
    > 
    > Is this still the case? Does anyone have a source for the practice of
    > leaving unknown communities alone or deleting them?

    https://tools.ietf.org/html/rfc7454#section-11

    Kind regards,

    Job

Remember policies between two peers may not be same as customer policies.

Example:  Customers_of_transit_X >>> Transit X >>> Peer_A >> Customers_of_Peer_A

Customers_of_Peer_A may use community A:50 to set local pref to 50 in Peer_A network.  But that doesn’t not mean Customers_of_transit_X can send A:50 to set lpref on their routes in Peer_A's network.  Peer_A's policy with Transit X likely does not take action on customer communities since they are 'peers' not customers.  Transit X can send A:50 to Peer_A but nothing would happen.  What's the benefit of Transit X preserving A:50 from its customers if it means nothing in Transit X?