BGP Community String for Telehouse AS8235

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BGP Community String for Telehouse AS8235

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BGP Community String Support

Important: TIX Route Server does NOT prepend it's AS by default!

To influence this policy you have these BGP communities available:

1. Prepend TIX AS8235 to *all* TIX-Peers

set community 8235:65500

2. Prepend TIX AS8235 to *selected* TIX-Peer N-times

set community 6550N:AAAA (N can be 1 to 3)

3. Do *not* announce to TIX-Peers with AS AAAA

set community 8235:AAAA

4. Do *not* announce to *ANY* TIX-Peers

set community 8235:65535

TIX set's these BGP communities to identify from where it learned a route:

1. From which TIX-Peer AAAA the route has been learned

8235:AAAA

2. From which TIX-Peer Class the route has been learned

8235:65000 ISP-Peers
8235:65010 Enterprise-Peers

By default routes from one class are *not* announced to the other classes.
For direct access to the .CH secondary nameserver it is mandatory to peer with AS8235.

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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 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

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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