Routing BGP BGP Community Attributes List BGP Community String for Time Warner Telecom AS4323
Saturday, 24 March 2007 20:38 | 
Written by ip Balance | 
| 
BGP Community String
Local Preference
BGP Community String
Description
4323:80
Set Local Preference in AS4323 to 80
4323:100
Set Local Preference in AS4323 to 100
4323:120
Set Local Preference in AS4323 to 120
4323:187
Blackhole BGP Community -- Used only for /32 hosts
4323:555
Advertise to External Peers and Backbone Customers
4323:666
Keep with in TWTC backbone
AS prepend
BGP Community String
Description
4323:1
Prepend AS4323 once
4323:2
Prepend AS4323 twice
4323:3
Prepend AS4323 three times
Network Operations E-mail: support@twtelecom.net
Network Operations Phone: 800-898-6473 (24/7)
Network Operations Phone (International): 1-303-542-6381 (24/7)
Peering E-mail: peering@twtelecom.net
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.
| < Prev | Next > |
|---|
Last Updated (Sunday, 20 November 2011 00:03)
