On Wed, Mar 6, 2019 at 8:32 Smith, Courtney <courtney_sm...@comcast.com> wrote:
> On 3/5/19, 6:04 PM, "NANOG on behalf of Job Snijders" > <nanog-bounces+courtney_smith=comcast....@nanog.org on behalf of > j...@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 > > > 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? OP didn’t specify what kind of BGP communities they were referring to. In general we can separate communities into two categories: “Informational” and “Action”. You are right that preserving/propagating “action” communities (such as in your example) probably isn’t that interesting. “informational” communities on the other hand can be very valuable. See https://tools.ietf.org/html/rfc8195 for more information on how the two types differ. Kind regards, Job
