This document has been extracted from User Guide V5.pdf.


Local Preference

All customer routes announced to Cogent will have a local pref of 130.

The customer can control the local preference for their announcements by using a community string that is passed to Cogent in the BGP session. The following table lists the community strings and the corresponding local preference that will be set when they are used.

Community StringLocal PrefEffect
174:1010Set customer route local preference to 10 (below everything-least preferred)
174:7070Set customer route local preference to 70 (below peers)
174:120120Set customer route local preference to 120 (below customer default)
174:125125Set customer route local preference to 125 (below customer default)
174:135135Set customer route local preference to 135 (above customer default)
174:140140Set customer route local preference to 140 (above customer default)

AS Padding

Customers with public AS numbers may pad their AS path to control the desirability of their connections. Customers with an assigned private AS number from Cogent may not pad their AS path. Cogent will ignore any padding of private AS numbers from customers.


Customers can control the "no-export" settings of their routes with the following community strings:

Community StringEffect
174:970Do not send route to NA (North America) - not accepted in NA.
174:971Do not send route to NA peers.
174:975Set local preference to 10 in NA.
174:980Do not send route to EU (Europe) - not accepted in EU.
174:981Do not send route to EU peers.
174:985Set local preference to 10 in EU.
174:990Do not send route to BGP customers, or peers.
174:991Do not send route to peers.

Peer Controls

Effective on ALL peer, non-granular.

Community StringEffect
174:3000Do not announce.
174:3001Prepend 174 1 time.
174:3002Prepend 174 2 times.
174:3003Prepend 174 3 times.

Route suppression, effective on specific peers, granular.

Community String Effect Common Name ASN
174:3000 Do not announce to all peers all 0
174:3010 Do not announce to NTT NTT 2914
174:3020 Do not announce to Virginmedia-NTL Virginmedia-NTL 5089
174:3030 Do not announce to Level3 Level3 3356
174:3040 Do not announce to Telefonica Telefonica 12956
174:3050 Do not announce to France Telecom France Telecom 5511
174:3060 Do not announce to Zayo Zayo 6461
174:3070 Do not announce to Sprint Sprint 1239
174:3080 Do not announce to Telia Telia 1299
174:3090 Do not announce to Verizon Verizon 701
174:3100 Do not announce to KPN KPN 286
174:3110 Do not announce to UUNet EU UUNet EU 702
174:3120 Do not announce to Tiscali Tiscali 3257
174:3130 Do not announce to DTAG DTAG 3320
174:3140 Do not announce to Global Crossing Global Crossing 3549
174:3150 Do not announce to Teleglobe Teleglobe 6453
174:3160 Do not announce to ATT ATT 7018
174:3170 Do not announce to UPC UPC 6830
174:3180 Do not announce to Google Google 15169
174:3190 Do not announce to CW CW 1273
174:3200 Do not announce to Cablevision Cablevision 6128
174:3210 Do not announce to Qwest/Centurylink Qwest 209
174:3220 Do not announce to TelecomItalia TelecomItalia 6762
174:3230 Do not announce to Savvis Savvis 3561
174:3240 Do not announce to Bellnexxia Bellnexxia 577
174:3250 Do not announce to TDC TDC 3292
174:3260 Do not announce to Tele2 Tele2 1257
174:3270 Do not announce to XO XO 2828
174:3280 Do not announce to Telus Telus 852
174:3290 Do not announce to China Telecom China Telecom 4134
174:3300 Do not announce to Comcast Comcast 7922

Other Communities

Routes announced to customers by Cogent will have one of the following communities associated with them:

Community StringDescription
174:21000Route is learned from NA (North America) non-customer.
174:21001Route is NA internal or customer route.
174:21100Route is learned from EU (Europe) non-customer.
174:21101Route is a EU internal or customer route.

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