BGP Community String for Abilene AS11537

   February 22, 2007  Leave a comment

Attention

This BGP Community string information might be outdated. Please contact Abilene AS11537 to get more recent one. This BGP communites is ONLY for the customer who has BGP with Abilene AS11537. www.ipbalance.com is not maintaining this BGP Community string.

 

Abilene BGP communities

The following represents Abilene’s understanding of its own BGP community settings and how Abilene, STAR TAP, and CA*net3 set and receive BGP communities of peer networks with respect to each other. Abilene, CA*net3, and STAR TAP set BGP communities to indicate prefixes’ status and exchange prefixes with each other as described in the ITN program description set forth at http://international.internet2.edu/intl_connect/index.html#itn.
Abilene advertises to STAR TAP and CA*net3 all of its ITN-peer prefixes; CA*net3 and STAR TAP advertise to Abilene only those ITN-peer prefixes from networks which have MoUs with Abilene. Abilene BGP community values are set (additively) for a given prefix. See "show ip bgp " in the Abilene router proxy for real-world examples.
Abilene-connected Gigapops and connectors with heterogeneous participants (i.e. not all are universities) may need to use these BGP communities to help them pass prefixes appropriately to their participants. For example, connectors can pass all prefixes on to their university participants, but should not pass commercial or US Fednet prefixes to their commercial or Fednet participants. Beginning in February 2002, Abilene allows its peers to use BGP communities to influence Abilene’s preference-setting for prefixes. See table 2 below for details.

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
YES
YES
YES
YES
11537:910 Abilene SEGP sponsored educational groups (primarily state networks)
YES
YES
YES
YES
11537:911
 Black Hole
 Traffic to these prefixes will be discarded
 no no
 no
 no
11537:950 Abilene_DC
all Abilene connected participants
YES
YES
YES
YES
11537:2000 Commercial commercial research-lab participant
YES
YES
YES
no
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
no
11537:2500 non Transit non-ITN (and non-US) peer network
no
no
YES
YES
11537:2501 Transit ITN(non-US) peer network
no
YES
YES
YES
11537:3000 FEDNET US federal peer network
no
no
YES
YES
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.


 


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