BGP Community String for SK Slovak Telecom AS6855

   March 6, 2007  Leave a comment

Attention

This BGP Community string information might be outdated. Please contact SK Slovak Telecom  AS6855 to get more recent one. This BGP communites is ONLY for the customer who has BGP with SK Slovak Telecom  AS6855. www.ipbalance.com is not maintaining this BGP Community string.


BGP Community String to control traffic

6855:1101 Do not announce to SIX
6855:1102 Do not announce to DT AS3320
6855:1103 Do not announce to BTN AS3491
6855:1104 Do not announce to Tiscali AS3257
6855:1201 Prepend 6855 when announcing to SIX
6855:1202 Prepend 6855 when announcing to DT AS3320
6855:1203 Prepend 6855 when announcing to BTN AS3491
6855:1204 Prepend 6855 when announcing to Tiscali AS3257
6855:1301 Prepend 6855 6855 when announcing to SIX
6855:1302 Prepend 6855 6855 when announcing to DT AS3320
6855:1303 Prepend 6855 6855 when announcing to BTN AS3491
6855:1304 Prepend 6855 6855 when announcing to Tiscali AS3257
6855:50 SET_LOCAL_PREFERENCE to 50
6855:90 SET_LOCAL_PREFERENCE to 90


LOC_PREF settings

50 Customer routes – GLOBAL BACKUP
60 Upstream providers
70 Peering partners
90 Customer routes – BACKUP links with ST AS6855
100 Customer routes – PRIMARY connections

Other:

DSCP = 0 on ANY connection
(upstream, peer, customers, dial customers, VPN customers)

================
Route colouring:

6855:2401 Routes from SIX peering
6855:2402 Routes from DT
6855:2403 Routes from BTN
6855:2404 Routes from Tiscali
6855:2700 Default route


POP NAME POP ID PA comm strings PI comm strings
<name> xx 6855:26xx 6855:25xx

 

 

 


Applying BGP Community string with sample configuration

 

1. Get the latest BGP community string from your ISP/upstream provider or check www.ShowipBGP.com

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.

 

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