Last Updated: August 23, 2006 Version 1.96

GBLX Customer BGP Communities

Table of Contents

Control of GBLX BGP Attributes
Control of Route Propagation

Control of GBLX BGP Attributes

 GBLX allows customers to modify various attributes of their announced prefixes within the GBLX network. Customers can alter the local preference of their prefixes, thus changing whether a prefix is chosen as the preferred route. However, many external influences can affect whether any given prefix is chosen as the best route. If you are multihomed and GBLX hears your route(s) from another provider and you alter your local preference to a value lower than the peer's value, the peer learned prefix will be chosen.

In order for you to appropriately manipulate your local preference values, the following is the standard policy applied for GBLX network customers and peers:

Customers:
Local Preference : 300
Metric Policy : Accept customers' metrics

Peers:
Local Preference : 200
Metric Policy : Do not accept peers' metrics.

Community Action
3549:100 set local preference 100
3549:200 set local preference 200
3549:275 set local preference 275
3549:300 set local preference 300
3549:350 set local preference 350

Control of Route Propagation

 GBLX provides the customer limited control over how their prefixes are propagated to various network peers. This is accomplished using as-path prepending at the GBLX-Peer border. The following communities may be sent to prepend customer announced prefixes:

Community Action
3549:600 Deny inter-continental export of tagged prefix [iBGP].
3549:666 Deny inter-as export of tagged prefix (deny to peers, send to customers) [eBGP].

For a limited subset of GBLX peering connections, more granular control of announcements is provided. If GBLX sees a community matching 3549:8..., routing announcements sent to the following listed ASNs will be modified according to these rules :

 ASN  Peer  No Export   Prepend +1   Prepend +2   Prepend +3 
174 Cogent 8280 8281 8282 8283
209 Qwest 8010 8011 8012 8013
577 Bellnexxia 8090 8091 8092 8093
701 MCI 8030 8031 8032 8033
1239 Sprint 8060 8061 8062 8063
1257 Tele2 8110 8111 8112 8113
1299 TeliaSonera 8250 8251 8252 8253
1668 AOL 8070 8071 8072 8073
2497 JPNIC 8080 8081 8082 8083
2516 KDDI 8100 8101 8102 8103
2828 XO 8260 8261 8262 8263
2914 NTT Verio 8120 8121 8122 8123
3257 Tiscali 8240 8241 8242 8243
3300 InfoNet Europe 8130 8131 8132 8133
3303 Swisscom 8140 8141 8142 8143
3320 DTAG 8150 8151 8152 8153
3356 Level 3 8160 8161 8162 8163
3561 Savvis 8170 8171 8172 8173
4134 ChinaNet 8230 8231 8232 8233
5511 OpenTransit 8190 8191 8192 8193
6453 Teleglobe 8210 8211 8212 8213
6461 AboveNet 8200 8201 8202 8203
6762 Seabone (TI) 8050 8051 8052 8053
6830 UPC/Chello 8180 8181 8182 8183
7018 AT&T (US) 8220 8221 8222 8223
7473 Singtel 8040 8041 8042 8043
7911 Wilcom 8020 8021 8022 8023
12956 Telefonica 8270 8271 8272 8273

This example below illustrates the use of these communities.

A customer with ASN 65535 sends GBLX a route tagged with communities  "3549:8011 3549:8033 3549:8190"

When that route is reannounced across GBLX peering connections:



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