BGP Community String for GRNET AS5408

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BGP Community String for GRNET AS5408

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List of all BGP communites used by GRNET:
NO_EXPORT
NO_ADVERTISE
5408:666 Blackhole this route (for /32 only)
5408:120 Primary Link (Higher Local Preference)
5408:110 Backup Link (Lower Local Preference)
5408:1001 Routes received from GEANT
5408:1002 Routes received from AIX
5408:1003 Routes received from GRNET clients
5408:2005 Prepend 5 times
5408:3003 Prepend 3 times when announcing to AIX
5408:3005 Prepend 5 times when announcing to AIX
5408:4001 Don't announce to AIX
5408:4005 Don't announce to GEANT

BGP communities available to GRNET clients:
5408:110 Backup Link (Lower Local Preference)
5480:666 Blackhole this route (for /32 only)
5408:2005 Prepend 5 times
5408:3003 Prepend 3 times when announcing to AIX
5408:3005 Prepend 5 times when announcing to AIX
5408:4001 Do not announce to AIX
5408:4005 Do not announce to GEANT

BGP communities available to AIX Peers:
5408:120 Prefer this route (for GRNET clients multihomed to AIX)

BGP communities available to GEANT:
5408:120 Prefer this route
(for GRNET clients multihomed to GEANT, eg SEEREN)

BGP communities automatically appended by GRNET
!!! Note: These BGP communities are only supposed to be appended by GRNET.
Incoming routes with such BGP communities may be filtered.
5408:1001 Routes received from GEANT
5408:1002 Routes received from AIX
5408:1003 Routes received from GRNET Clients

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 [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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