To manage route announcements via BGP communities, CNX's route servers support specific community tags that allow peers to control the propagation of their prefixes. By applying these communities, peers can specify how their routes are handled within the exchange.
- Currently the CNX route servers supports multiple communities that can be used to affect how routes are propagated to CNX members.
- See the automatically generated route server policy for details.
- RFC8092 Large Communities are supported on all route servers
- We recommend the use of large communities where possible since they can be used for CNX members with 32-bit ASN.
Announcement control via BGP communities
- Routes tagged with the NO_EXPORT or NO_ADVERTISE communities received by the route server are propagated to other clients with those communities unaltered.
- Routes tagged with the GRACEFUL_SHUTDOWN BGP community (65535:0) have their LOCAL_PREF attribute lowered to 0.
| Function | Standard | Extended | Large |
|---|---|---|---|
| Do not announce to any client | 0:65534 | rt:0:65534 | 132213:0:0 |
| Announce to peer, even if tagged with the previous community | 65534:peer_as | rt:65534:peer_as | 132213:1:peer_as |
| Do not announce to peer | 0:peer_as | rt:0:peer_as | 132213:0:peer_as |
| Prepend the announcing ASN once to peer | 65511:peer_as | rt:65511:peer_as | 132213:101:peer_as |
| Prepend the announcing ASN twice to peer | 65512:peer_as | rt:65512:peer_as | 132213:102:peer_as |
| Prepend the announcing ASN thrice to peer | 65513:peer_as | rt:65513:peer_as | 132213:103:peer_as |
| Prepend the announcing ASN once to any | 65501:65534 | rt:65501:65534 | 132213:101:0 |
| Prepend the announcing ASN twice to any | 65502:65534 | rt:65502:65534 | 132213:102:0 |
| Prepend the announcing ASN thrice to any | 65503:65534 | rt:65503:65534 | 132213:103:0 |
| Add NO_EXPORT to peer | 65281:peer_as | rt:65281:peer_as | 132213:65281:peer_as |
| Add NO_ADVERTISE to peer | 65282:peer_as | rt:65282:peer_as | 132213:65282:peer_as |