BGP large communities

CNX documents large communities as its route-server control interface. In the tables below, <PEER_ASN> is the ASN of the route-server client affected by the control. <TARGET> is either a peer ASN or 0 for all clients.

Propagation controls

Action	Large community
Do not announce to any route-server client	`132213:0:0`
Announce to one peer as an exception to the previous control	`132213:1:<PEER_ASN>`
Do not announce to one peer	`132213:0:<PEER_ASN>`
Do not announce to domestic peers	`132213:0:65528`
Do not announce to non-domestic peers	`132213:0:65529`

The per-peer exception is meaningful when used with 132213:0:0.

AS-path prepend controls

Action	One peer	All peers
Prepend announcing ASN once	`132213:101:<PEER_ASN>`	`132213:101:0`
Prepend announcing ASN twice	`132213:102:<PEER_ASN>`	`132213:102:0`
Prepend announcing ASN three times	`132213:103:<PEER_ASN>`	`132213:103:0`

Per-export MED controls

MED applied by CNX	Large community
10	`132213:901:<TARGET>`
20	`132213:902:<TARGET>`
30	`132213:903:<TARGET>`
40	`132213:904:<TARGET>`
50	`132213:905:<TARGET>`

Use one MED community per target. CNX removes communities in its internal 132213:900-999:* control range before export.

Add a well-known community on export

Action toward one peer	Large community received by CNX
Add `NO_EXPORT` to the route exported to that peer	`132213:65281:<PEER_ASN>`
Add `NO_ADVERTISE` to the route exported to that peer	`132213:65282:<PEER_ASN>`

These controls cause CNX to add the corresponding well-known community to the copy exported to the selected route-server client. They do not affect a bilateral session.

Communities CNX attaches

Location and participant class

Meaning	Large community
Recipient and route next hop are at the same CNX site	`132213:65527:0`
Route received from a domestic participant	`132213:65528:0`
Route received from a non-domestic participant	`132213:65529:0`

CNX removes member-supplied copies of these markers before applying its own classification.

Registry and origin-validation state

Meaning	Large community
Prefix is present in the member's derived IRR set	`132213:64512:11`
Prefix is not present in the member's derived IRR set	`132213:64512:10`
Origin is present in the member's derived AS-SET	`132213:64512:21`
Origin is not present in the member's derived AS-SET	`132213:64512:20`
Prefix was validated using a covering ROA as a route object	`132213:64512:31`
Prefix was validated using the Registro.br dataset	`132213:64512:61`
Route was accepted through an explicit whitelist	`132213:64512:41`
ROV Valid	`132213:1000:1`
ROV NotFound/Unknown	`132213:1000:2`
ROV not performed	`132213:1000:3`
ROV Invalid	`132213:1000:4`

RPKI Invalid routes are rejected rather than exported as ordinary usable routes. Validation and reject markers are primarily useful through route-server diagnostics and the looking glass.

Reject-reason communities

Rejected routes are tagged 132213:65520:<REASON> in route-server diagnostic views.

Reason	Meaning
0	Generic rejection
1	Invalid AS-path length
2	Bogon prefix
3	Globally blacklisted prefix
4	Invalid address family
5	Invalid next hop
6	Invalid left-most ASN
7	Invalid ASN in the AS path
8	Transit-free ASN found in an invalid AS-path position
9	Origin ASN not authorized by the member's AS-SET
10	IPv6 prefix outside global unicast space
11	Prefix in the member-specific blacklist
12	Prefix not authorized by the derived IRR set
13	Invalid prefix length
14	RPKI Invalid route
15	Route-server ASN found where policy forbids it
16	ASPA Invalid AS path; reserved for ASPA enforcement
65535	Unknown or hook-defined rejection

Diagnostic views may also carry 132213:65499:<ANNOUNCING_ASN> to identify the member ASN from which a rejected route was received. These diagnostic markers are not steering controls.

Well-known communities

CNX honors the standard GRACEFUL_SHUTDOWN community 65535:0 by lowering route-server local preference to zero. The generated policy also recognizes the RFC 7999 BLACKHOLE community 65535:666; blackhole routes are propagated unchanged with NO_EXPORT. Acceptance by another member remains subject to that member's policy.