BGP Communities

Use Border Gateway Protocol (BGP) communities to control BGP traffic

Informational Communities

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:

23352:TCRPP

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.

VALUE RELATIONSHIP CONTINENT REGION
0 All All
1 Transit North America North-West
2 Public Peer Europe North
3 Private Peer Asia North-East
4 Customer Australia West
5 Internet South America Central
6 Africa East
7 Middle East South-West
8 South
9 South-East

 

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
20 AMS Amsterdam, Netherlands
21 TKO Tokyo, Japan
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
32 FRA Frankfurt, Germany
33 CDG Paris, France
34 BOS Boston MA, United States

Action Communities

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

ACTION CODE ACTION
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)

 

TARGET ASN MEANING
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?
COMMUNITY MEANING
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
NOTES
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

Other Communities

These miscellaneous communities don’t fit in any other format.

 

COMMUNITY MEANING
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
23352:5000 Anycast

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Questions or comments regarding ServerCentral’s BGP communities can be sent to systems@servercentral.com.

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