Use Border Gateway Protocol (BGP) communities to control BGP traffic
Informational Communities convey how and where a route was learned by our network.
They always have 5 digits in the second half and use the following structure:
T – The type of relationship through which the route was learned.
C – The continent in which the route was learned.
R – The region of the continent in which the route was learned.
PP – The POP city code in which the route was learned.
|CITY CODE||CITY/POP IDENTIFIER||CITY STATE/PROVINCE, COUNTRY|
|11||IAD||Ashburn VA, United States|
|12||NYC||New York NY, United States|
|13||SJC||San Jose CA, United States|
|14||PAO||Palo Alto CA, United States|
|15||SFO||San Francisco CA, United States|
|16||ORD||Chicago IL, United States|
|17||DFW||Dallas/Forth Worth TX, United States|
|18||LAX||Los Angeles CA, United States|
|19||EWR||Newark NJ, United States|
|22||LHR||London, United Kingdom|
|23||ATL||Atlanta GA, United States|
|24||PHX||Phoenix AZ, United States|
|25||MTL||Montreal QC, Canada|
|26||TOR||Toronto ON, Canada|
|27||IAH||Houston TX, United States|
|28||SEA||Seattle WA, United States|
|29||DEN||Denver CO, United States|
|30||MIA||Miami FL, United States|
|31||SLC||Salt Lake City UT, United States|
|34||BOS||Boston MA, United States|
Action Communities are optional communities for controlling route attributes and how they’re exported to other networks.
Action Communities can be targeted to specific peer ASNs, locations (by continent, region, city), or classes of neighbors (transits, peers, customers). They always have 4 digits in the second half and use the following structure:
ASN:A0CR or ASN:A1PP
A – The action code to be performed
C – The target continent
R – The target region
PP – The target POP city code
|1||Prepend AS-PATH with 23352 on export|
|2||Prepend AS-PATH with 23352 23352 on export|
|3||Prepend AS-PATH with 23352 23352 23352 on export|
|4||Prepend AS-PATH with 23352 23352 23352 23352 on export|
|5||Set Multi-Exit Discriminator (MED) to 0 on export|
|6||Do not export|
|9||Override a Do Not Export (action code 6)|
|23352||Apply action to all neighbor ASNs|
|#####||Apply action to a specific ASN #####|
|65001||Apply action to all Transits|
|65002||Apply action to all Peers|
|65003||Apply action to all Customers|
How do I use Action Community tags with multiple criteria?
|23352:1000||Prepend once to all BGP neighbors globally|
|23352:2010||Prepend twice to all BGP neighbors in North America|
|23352:3111||Prepend three times to all BGP neighbors in Ashburn, VA|
|3549:6000||Do not export to AS3549/Global Crossing globally|
|65001:6020||Do not export to any IP Transit neighbors in Europe|
Local Preference Communities
Local Preference Communities are values that influence the best-path selection of BGP prefixes. The local-preference attribute only applies to path selection within ServerCentral’s network. A value of 50 will create a backup route that’s neither used nor propagated to the rest of the Internet, only becoming active if no other route is heard.
|COMMUNITY||LOCAL PREFERENCE SETTING
|23352:50||Set local-preference to 50||Backup route only|
|23352:100||Set local-preference to 100||Default transit route|
|23352:150||Set local-preference to 150||Less than peer, more than transit|
|23352:200||Set local-preference to 200||Default peer route|
|23352:250||Set local-preference to 250||Less than customer, more than peer|
|23352:300||Set local-preference to 300||Default customer route|
|23352:350||Set local-preference to 350||Preferred above other customers|
These miscellaneous communities don’t fit in any other format.
|23352:69||Multihomed Customer Advisory Tag (this is used to automatically indicate any known issues, such as congestion or routing problems, so that multi-homed customers can match this community and divert traffic to another path)|
|23352:666||Null route all traffic to this prefix (requires a pre-established session with a BGP blackhole server)|
|23352:998||Within the ServerCentral network, do not export the prefix outside of the current continent|
|23352:999||Within the ServerCentral network, do not export the prefix outside of the current region|