Network Connectivity

Informational Communities are BGP communities added by ServerCentral, in order to convey information about how and where the route was initially learned by our network. These communities will always have 5 digits in the second half, and are constructed in the following format:

23352:TCRPP

T - The type of relationship that the route was learned through.
C - The continent where the route was learned.
R - The region of the continent where the route was learned.
PP - The POP code (city) where the route was learned.

Action Communities are optional communities which may be added by ServerCentral customers, to control route attributes or to control how routes are exported to other networks. These communities may also be targetted to specific peer ASNs, specific locations (by continent, region, or city), or specific classes of neighbors (transits, peers, or customers). Action Communities are always 4 digits in length in the second half and have the following structure:

#####:A0CR
-or-
#####:A1PP

##### The Target ASN
A - The action code to be performed
C - The target continent (same table as above)
R - The target region (same table as above)
PP - The target POP (city code, same table as above)

Action Community Examples

The following examples illustrate how to use Action Community tags with multiple criteria:

Local Preference Communities are values which influence the best-path selection of BGP prefixes. The local-preference attribute is not transitive, so this applies only to path selection within the ServerCentral network. A value of 50 will create a "backup route" that is never used or propagated to the rest of the Internet, so long as any other path is heard for the prefix in question. This route will only become active if no other route is heard.

These are miscellaneous communities which do not fit into any of the formats above. The Multihomed Customer Advisory Tag is used to automatically indicate any known issues, such as congestion or routing problems, so that multihomed customers can match this community and divert traffic to another path, if possible.