Home

Routing

BGP Community Attributes List

BGP Community String for InSat GmbH AS20535

Google Translation

Main Menu

Login Form

Yahoo Network

Merchant Solutions

Latest Articles

100 customers (default)
70 upstreams
60 use AS20535 as backup only

BGP community list

Control localpref in the AS20535 backbone
20535:60 Set localpref to 60 (use AS20535 as backup)
20535:70 Set localpref to 70

Control announces to peer NN
20535:1NNx

Route is learned from peer NN
20535:2NN

x is number of prepends (1, 2, 3) or do not announce (0)
NN is
01 Telia-Sonera (AS1299)
02 Level3 (AS3356)

Route is learned from upstream, do not announce it to other upstreams.
20535:2000

AS20535 does not accept or announce prefixes longer than 24 bits

Applying BGP Community string with sample configuration

1. Get the latest BGP community string from your ISP/upstream provider or check new.CiscoNET.com web site.

2. Pick the best BGP community string for your traffic shaping plan (mainly incoming traffic). Most of ISPs are providing 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 20535:70 or 20535:3 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-AS20535 permit 10
router(config-route-map)#match ip address 10

router(config-route-map)#set community 20535:70 <------ using Local Preference
or
router(config-route-map)#set community 20535:3 <--------- using AS prepending

router(config-route-map)#route-map to-AS20535 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-AS20535 out
router(config-router)#exit
router(config)#exit
router#copy running-config startup-config

4. And then, go to www.CiscoNET.com 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.

Add as favourites (34) | Views: 498 | E-mail

Comments (1)

1. Comment 13 239
Written by This e-mail address is being protected from spam bots, you need JavaScript enabled to view it , on 12-08-2007 19:39
Helo1l, great site!

Report