BGP Communities

The use of BGP communities are helpful in manipulating traffic flows. They are commonly used to determine and avoid congestion or network failure. CRNC utilizes BGP communities over every BGP-enabled link. For more information please contact us at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

Transit
All Transitors	29838:1000
Voxel	29838:1001
Deprecated	29838:1002
nLayer	29838:1003
Deprecated	29838:1004
Deprecated/IHN	29838:1005
Mzima	29838:1006

Public Peering
All Public Peers	29838:2000
NYIIX	29838:2001
NYCX	29838:2002

Private Peering
All Private Peers	29838:3000
Latency Networks	29838:3001

Customer
Customer	29838:4000
NYC1 (Telehouse - 25 Broadway, New York, NY)	29838:4001
NJ1 (Equinix - 275 Hartz Way, Secaucus, NJ)	29838:4002
NYC2 (CRNC - 325 Hudson St, New York, NY)	29838:4003

CRNC Originated
CRNC Originated	29838:5000
NYC1 (Telehouse - 25 Broadway, New York, NY)	29838:5001
NJ1 (Equinix - 275 Hartz Way, Secaucus, NJ)	29838:5002
NYC2 (CRNC - 325 Hudson St, New York, NY)	29838:5003

All routes within the CRNC network carry a local preference

35	Depreferred Transit
40	Standard Transit
45	Preferred Transit
75	Depreferred Public Peering
80	Standard Public Peering
85	Preferred Public Peering
85	Depreferred Private Peering
90	Standard Private Peering
95	Preferred Private Peering
115	Depreferred Customer or CRNC Originated
120	Standard Customer or CRNC Originated
125	Preferred Customer or CRNC Originated

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 29838:120 or 29838:3 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-AS29838 permit 10
router(config-route-map)#match ip address 10

router(config-route-map)#set community 29838:120 <------ using Local Preference
or
router(config-route-map)#set community 29838:3 <--------- using AS prepending

router(config-route-map)#route-map to-AS29838 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-AS29838 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.

---

Please share this article with ;