BGP Communities to use by peers: (x = 1..3)

15833:1100 Do not announce to TELIA (AS1299)
15833:110x Prepend x times 15833 when announcing to TELIA
15833:1200 Do not announce to TPNET (AS5617)
15833:120x Prepend x times 15833 when announcing to TPNET
15833:1400 Do not announce to ATM (AS24748)
15833:140x Prepend x times 15833 when announcing to ATM
15833:1500 Do not announce to CYFRONET(AS8323)
15833:150x Prepend x times 15833 when announcing to CYFRONET
15833:1600 Do not announce to WIX/GIX/PL-IX
15833:160x Prepend x times 15833 when announcing to WIX/GIX/PL-IX
15833:1700 Do not announce to POZMAN (AS8364)
15833:170x Prepend x times 15833 when announcing to POZMAN

 

Applying BGP Community string with sample configuration

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 [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.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.

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