On Wed, Mar 31, 2021 at 06:02:52PM +0000, Jakob Heitz (jheitz) wrote: > No community is transitive. > Not even the transitive extended communities. > > In all BGP code I've worked in, not just Cisco, a configuration > is required to send communities of any kind to an ebgp session. > By default, no communities are sent to ebgp sessions. > That's a good thing, because network operators don't want > junk in the routes transiting across their networks, causing > churn and memory consumption.
Contrarily, the implementations I've worked on don't have this behavior. But it's still a highly relevant point and perhaps what should probably be a useful rule of thumb across IETF working groups that deal with BGP: Because such a knob exists on multiple implementations, communities SHOULD NOT be used for any protocol transient signaling behaviors. > Path attributes are transitive. > However, several years ago, approximately coinciding with the > development of RFC7660, there was massive thrust to get attributes > blocked too. Now we implement path attribute filtering > and many network operators use it. Sadly, also yes. At least in my case, every discussion I have about the feature I note that it is toxic to the incremental deployment of new features in BGP. And similarly, that it is a toxic use case for someone paying them as a transit provider. -- Jeff _______________________________________________ GROW mailing list [email protected] https://www.ietf.org/mailman/listinfo/grow
