Abilene BGP communities
BGP Community value | BGP Community name | Description | Prefixes passed to non-ITN peer nets | Prefixes passed to ITN peer nets | Prefixes passed to connectors | Prefixes passed to commercial participants |
11537:40/160 |
FED/ITN-pref |
Influence local-pref |
as usual |
as usual |
as usual |
as usual |
11537:140/260 |
Connector-pref |
Influence local-pref |
as usual | as usual | as usual | as usual |
11537:600 |
IPv6 special |
V6 prefixes learned via tunnels |
YES |
YES |
YES |
YES |
11537:902 | Sponsored | non-UCAID R&E sites sponsored for connection by members | ||||
11537:910 | Abilene SEGP | sponsored educational groups (primarily state networks) | ||||
11537:911 |
Black Hole |
Traffic to these prefixes will be discarded |
no | no |
no |
no |
11537:950 | Abilene_DC | |||||
11537:2000 | Commercial | commercial research-lab participant | ||||
11537:2001 |
Commercial Peer |
This prefix from a *peer network*, not a regular Abilene participant, is commercial. Examples may be AUP-free prefixes accepted for ipv6 or multicast peering. |
||||
11537:2002 |
Block tO Commercial |
Connectors may set this community for prefixes they pass to Abilene. Abilene will not advertise prefixes with this community to commercial peers. |
YES |
YES |
YES |
|
11537:2500 | non Transit | non-ITN (and non-US) peer network | ||||
11537:2501 | Transit | ITN(non-US) peer network | ||||
11537:3000 | FEDNET | US federal peer network | ||||
11537:3500 |
Connector Only |
Abilene uses this to mark prefixes sent to connectors but not peers |
no |
no |
YES |
YES |
Using BGP communities to influence Abilene’s local-preference setting: (these settings may be used for ipv4 or ipv6) Beginning February 2002, Abilene’s BGP peers may set BGP communities to influence Abilene’s setting of its local-preference for the prefixes we receive from you. The BGP community may cause the preference to be lower or higher than the default preferences, and may be useful in cases where we peer with you in more than one place and you want to influence our choice of paths to you. Refer to the table below for the BGP community to use and its result. For example, if you are an Abilene connector, the default local-pref for the prefixes we receive from you is set to 200. If you set a BGP community 11537:260 for some prefixes, Abilene will set the local-pref for that path to those prefixes at 260. Note: only the communities specified below are supported.
|
|||
---|---|---|---|
Default
|
High
|
Low
|
|
Abilene CONNECTORS set community to: … and Abilene’s local-pref for the associated prefixes will be: |
(none) 200 |
11537:260 260 |
11537:140
140 |
Abilene ITN/nonITN/FEDNET peers set community to: … and Abilene’s local-pref for the associated prefixes will be: |
(none)
100 |
11537:160
160 |
11537:40
40 |
IPv6 special BGP community String
Beginning November 2002, Abilene began setting a new BGP community, 11537:600, to indicate that prefixes with this BGP community come to Abilene through a tunneled interface.
"Black Hole” BGP community String:
Beginning November 2004, connectors may set a BGP community to communicate to Abilene that traffic to designated prefixes should be blackholed within Abilene. This is to allow some protection in DoS attacks. Connectors may only set this for their own prefixes.
Reference site : www.ucaid.edu/abilene/html/itnservice.html .
Applying BGP Community string with sample configuration
1. Get the latest BGP community string from your ISP/upstream provider or check www.ShowipBGP.com.
2. Pick the best BGP community string for your traffic shaping plan (mainly incoming traffic). Most of ISPs are providing BGP community string with local preference and AS prepending option. Cannot tell which one is better than the other. It will depend on your global traffic shaping plan.
3. Follow the below commands ( Cisco only )
The below Sample configuration will tag the 10.0.0.0/24 route with [ISP AS]:120 or [ISP AS]:3 and will not tag any other routes.
router#config t
router(config)#ip bgp-community new-format
router(config)#access-list 10 permit 10.0.0.0 0.0.0.255
router(config)#access-list 10 deny any
router(config)#route-map [to-ISP] permit 10
router(config-route-map)#match ip address 10
router(config-route-map)#set community [ISP AS]:120 <—- using Local Preference
or
router(config-route-map)#set community [ISP AS]:3 <——- using AS prepending
router(config-route-map)#route-map [to-ISP] permit 20
router(config-route-map)#exit
router(config)#router bgp [xxxx] <——————————- xxxx = customer’s ASN
router(config-router)#neighbor x.x.x.x send-community
router(config-router)#neighbor x.x.x.x route-map [to-ISP] out
router(config-router)#exit
router(config)#exit
router#copy running-config startup-config
4. And then, go to www.RouteServer.org and pick one of route server on the map to see your announcement. If you are using AS prepending option, you will see your AS prepends on route servers. Sometime you might not see your route with particular ISP path.
In most of case it might not be any routing problem, just the route path was dropped at somewhere by BGP best path selection scheme. Try Oregon route server, if you can see your route. The Oregon route server is providing many possible and available paths between BGP speakers and neighbors.
If you don’t see your route on there? check other route servers and also check your
BGP configuration. You might need to contact your upstream provider to check what they are learning BGP route from you.