BGP Communities Support Definitions for Customers
1. BGP Communities controlling Voyager GmbH Germany internal use of customer routes by means of local preference:
BGP community set local effect preference
12732:10 10 below everything, least prefered
12732:90 90 below peers
12732:400 400 below peering & customer default
12732:800 800 below customer default
12732:950 950 above customer default
2. BGP Communities controlling AS path prepending for customer routes on egress:
12732:1000 do not announce at BCIX
12732:1001 prepend one at BCIX
12732:1002 prepend two at BCIX
12732:2000 do not announce at FFM/DeCIX
12732:2001 prepend one at FFM/DeCIX
12732:2002 prepend two at FFM/DeCIX
12732:3000 do not announce at DUS/ECIX
12732:3001 prepend one at DUS/ECIX
12732:3002 prepend two at DUS/ECIX
3. BGP Communities tagging the source of routes
12732:10001 peer route, learned at BCIX
12732:10002 peer route, learned at ECIX
12732:10003 peer route, learned at WorkerX
12732:10008 normal path
12732:10009 backup path
12732:10021 peer route, learned in Duesseldorf
12732:10030 peer route, learned in Berlin
12732:10034 peer route, learned in Leipzig
12732:10040 peer route, learned in Hamburg
12732:10089 peer route, learned in Frankfurt
4. Others
Peerings (IPv4 & IPv6) are welcome 😉
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 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.