This document has been extracted from AS3320_BGP_Communities_v1.1.pdf.
IP Transit
AS3320 BGP Communities
Version: Issued: 1.1 22 August 2005
1 – Introduction
The Deutsche Telekom AS3320 Internet network (“AS3320”) provides the following BGP community based routing services to IP transit customer networks. A customer network can use these communities to influence routing decisions and manipulate traffic streams within AS3320. There are two general categories of communities:
- Signalling communities that are sent by a customer network to request certain routing services from AS3320.
- Informational communities that AS3320 sends to provide additional information about routes that is not available via other BGP attributes.
2 – Signalling Communities
2.1 – Blackholing
A customer network may request blackholing to defend against Denial of Service (DoS) and Distributed DoS attacks. Blackholing results in AS3320 discarding all traffic to the particular address space. Authorization by AS3320 backbone engineering is required to ensure the affected address space truly belongs to the customer network.
| Community Value | Name | Description |
| 65000:0 | Blackholing | AS3320 discards all traffic to the destination prefix(es). |
2.2 – NOPEER
This is the recently IETF defined community NOPEER[1]. A customer network can use this to restrict propagation of its routes to AS3320 peers.
| Community Value | Name | Description |
| 65535:65284 | NOPEER | Defined by RFC 3765. AS3320 will not propagate the tagged route(s) to its peers. |
[1] G. Huston, “NOPEER Community for BGP Route Scope Control,” RFC 3765, April 2004.
2.3 – Local Preference
A customer network can control the route priority within AS3320 for its advertisements by using the following Local Preference communities. Currently, AS3320 assigns the (standard) Local Preference value of 100 by default.
| Community Value | Name | Description |
| 65001:100 | Standard Local Preference | Set Local Preference to 100 (default). |
| 65001:50 | Low Local Preference | Set Local Preference to 50. |
| 65001:150 | High Local Preference | Set Local Preference to 150. Requires authorization from AS3320 backbone engineering. |
2.4 – Restrict Route Propagation
A customer network may use these communities to restrict propagation of its routes to AS3320 peers. However, the well known community NOPEER should be employed instead of these where appropriate.
| Community Value | Name | Description |
| 65010:X | No Export to AS X | Do not advertise route(s) to named AS3320 peer (ASN=X) |
| 65010:65001 | No Export by Class: Peer | Do not advertise route(s) to AS3320 peers. |
| 65010:65002 | No Export by Class: Upstream | Do not advertise route(s) to AS3320 upstream. |
| 65010:65003 | No Export by Class: Peer & Upstream | Do not advertise route(s) to AS3320 peers and upstream. |
2.5 – AS Path Prepending
AS path prepending is a common way of making routes less attractive since AS path length is usually one of the BGP path selection criteria. A customer network may use these communities to selectively request AS3320 to insert additional copies of the AS number 3320 when propagating the customer routes to neighbors.
| Community Value | Name | Description |
| 65012:X | AS Prepend 2x to AS X | Prepend 3320 two times to named peer (ASN=X) |
| 65013:X | AS Prepend 3x to AS X | Prepend 3320 three times to named peer (ASN=X) |
| 6501n:65001 | Prepend by Class: Peer | Prepend 3320 n times to peers. n=2 or 3. |
| 6501n:65002 | Prepend by Class: Upstream | Prepend 3320 n times to upstream. n=2 or 3. |
| 6501n:65003 | AS Prepend by Class: Peer & Upstream | Prepend 3320 n times to peers and upstream. |
| 6501n:65004 | AS Prepend by Class: Customer | Prepend 3320 n times to customers. |
| 6501n:65005 | AS Prepend by Class: Customer & Peer | Prepend 3320 n times to customers and peers. |
| 6501n:65006 | AS Prepend by Class: Customer & Upstream | Prepend 3320 n times to customers and upstream. |
| 6501n:65007 | AS Prepend by Class: All | Prepend 3320 n times to all AS3320 neighbors. |
3 – Informational Communities
3.1 – Route Classification
As information to customer networks, AS3320 sends region and country origins on the routes it advertises and indicates whether the route is imported from a customer, peer or upstream provider.
Route Classification by Region
| Community Value | Description |
| 3320:2010 | Imported in Europe |
| 3320:2020 | Imported in North America |
| 3320:2030 | Imported in Asia Pacific |
Route Classification by Country
| Community Value | Description |
| 3320:2010 | Imported in Europe |
| 3320:2020 | Imported in North America |
| 3320:2030 | Imported in Asia Pacific |
| 3320:1040 | Imported in Austria |
| 3320:1056 | Imported in Belgium |
| 3320:1124 | Imported in Canada |
| 3320:1203 | Imported in Czech Republic |
| 3320:1208 | Imported in Denmark |
| 3320:1246 | Imported in Finland |
| 3320:1250 | Imported in France |
| 3320:1276 | Imported in Germany |
| 3320:1344 | Imported in Hong Kong |
| 3320:1348 | Imported in Hungary |
| 3320:1380 | Imported in Italy |
| 3320:1392 | Imported in Japan |
| 3320:1528 | Imported in the Netherlands |
| 3320:1578 | Imported in Norway |
| 3320:1616 | Imported in Poland |
| 3320:1702 | Imported in Singaporey |
| 3320:1724 | Imported in Spain |
| 3320:1752 | Imported in Sweden |
| 3320:1756 | Imported in Switzerland |
| 3320:1826 | Imported in Great Britain |
| 3320:1840 | Imported in the USA |
Route Classification by Neighbor Type
| Community Value | Description |
| 3320:9010 | Imported from a customer |
| 3320:9020 | Imported from a peerr |
| 3320:9030 | Imported from a upstream provider |