BGP communities are a powerful mechanism for signaling route policy preferences to the route server. At IXPN, members can use standard 16-bit or large 32-bit communities to control which peers receive their prefixes and to influence path selection via AS path prepending. This guide documents all BGP communities currently supported at IXPN.

Note: In the tables below, peer-as refers to the ASN of the target peer you wish to control advertisement to. IXPN’s ASN is 36932 .

Standard Communities

Standard BGP communities use the local-as:value format as defined in RFC 1997. These are the most widely supported community type.

CommunityDescription
0:peer-asPrevent advertisement of a prefix to peer-as
0:36932Prevent advertisement of a prefix to all peers
36932:peer-asAdvertise a prefix to peer-as only (used in conjunction with 0:36932)
36932:36932Advertise a prefix to all peers (implicit default)
40027:40000Advertise a prefix to Netflix (This allows members to consume Netflix content from IXPN)

Example: Announce to a Single Peer Only

To announce your prefix exclusively to AS 64500, you would attach:

0:36932          → Block announcement to all peers
36932:64500      → Then selectively allow AS 64500

This is a “deny all, then permit one” approach. First, 0:36932 suppresses advertisement to everyone, then 36932:64500 creates an exception for the specific peer.

Note: As many networks now operate with 32-bit ASNs, we strongly recommend using BGP Large Communities instead of the standard 16-bit communities. Do not mix standard and Large Communities within the same routing policy, choose one format and use it consistently.

Large Communities

Large communities use the global-admin:function:parameter format as defined in RFC 8092. They offer 32-bit fields, making them compatible with 4-byte ASNs.

CommunityDescription
36932:0:peer-asPrevent advertisement of a prefix to peer-as
36932:0:0Prevent advertisement of a prefix to all peers
36932:1:peer-asAdvertise a prefix to peer-as only (used in conjunction with 36932:0:0)
36932:1:0Advertise a prefix to all peers (implicit default)

Example: Block a Specific Peer

To prevent your prefix from being advertised to AS 64500 while still announcing to all other peers:

36932:0:64500    → Block announcement to AS 64500 only

All other peers will continue to receive the prefix normally.

Path Prepending with Large Communities

Path prepending allows you to make a route less preferred by artificially lengthening the AS path. This is useful for traffic engineering — for example, making a backup path less attractive than the primary.

CommunityDescription
36932:101:peer-asPrepend AS path to peer-as once
36932:102:peer-asPrepend AS path to peer-as twice
36932:103:peer-asPrepend AS path to peer-as three times

Example: Influence Inbound Traffic

If you peer with AS 64500 at two IXPs and want to make IXPN the backup path:

36932:102:64500  → Prepend twice toward AS 64500 at IXPN

AS 64500 will see a longer AS path for your prefixes via IXPN, preferring the other IXP for inbound traffic.

Quick Reference

Here is a consolidated view of all action codes used in IXPN’s large community scheme:

Action CodeMeaning
0Do not advertise (deny)
1Advertise (permit)
101Prepend once
102Prepend twice
103Prepend three times

Need Help?

If you have questions about configuring BGP communities for your peering sessions at IXPN, reach out to our technical team at noc@ixpn.ng.