Operational BGP Communities

Operational BGP Communities

Operational BGP Communities can be used to control various functions of the route server, such as redistribution of advertised prefixes, based on your ASN:-

  • control the redistribution of advertised prefixes, based on an ASN

Please note that if the $PEER-AS is a four byte AS number you have to use the BGP Extended or Large Communities.

 

All BGP community examples on this page are based on DE-CIX Mumbai (AS59200).
If you want to use BGP Communities at one of the other exchanges, please replace all occurrences of "59200" with the AS of the exchange:

IX-

AS

Mumbai

59200

Chennai

24470

Delhi

24457

Kolkata

24508

 

Control of prefix redistribution

You can control which BGP announcements you send to the route servers are redistributed to other peers. This can be done based on the following criteria:

  • ASN

  • General

The redistribution can be controlled with BGP CommunitiesBGP Extended Communities and BGP Large Communities.

The following table gives an overview of available options and their corresponding BGP Communities. In case two or more BGP (extended/large) Communities are contradicting the community with the lowest evaluation order is processed.

The same is true for every occurrence of "59200" on this page: Insert the AS of the Internet exchange route server for the exchange where you want to use our supported communities. The examples and descriptions are based on Mumbai

Evaluation Order 

Group

Action

BGP Standard Community (RFC 1997) 

BGP Extended Community (RFC 4360)

BGP Large Community (RFC 8092)

1 ASN based

Do not redistribute to $PEER-AS

0:$PEER-AS

rt:0:$PEER-AS **

59200:0:PEER-AS

2

Redistribute to $PEER-AS*

59200:$PEER-AS

rt:59200:$PEER-AS

59200:1:$PEER-AS

 
3 General

Do not redistribute

0:59200

rt:0:59200 **

59200:0:0

4

Redistribute to all (default)

59200:59200

rt:59200:59200

59200:1:0

* Only useful in combination with one or more "do not announce" BGP Communities with lower priority that will allow an override e.g. 59200:$PEER

** This is not supported by some hardware vendors. In this case we also provide this function in the form rt:65534:$PEER-AS and rt:65534:59200

The route servers remove the aforementioned BGP Communities and BGP Extended Communities from a BGP announcement before re-distributing it.

More than one of the aforementioned BGP Communities and BGP Extended Communities can be added to a single BGP announcement. DE-CIX recommends not to add more than 50 of these communities as it makes handling complex and error-prone. If you need to do this, please contact Customer Service

All BGP Communities and BGP Extended Communities that are not listed above are not touched by the route servers and transparently re-distributed. For backwards compatibility, routes with no community at all are distributed to all peers as well

You can check this in the DE-CIX Looking Glass. If you type your ASN into the global search field, you will find all matching prefixes from all DE-CIX route servers on all DE-CIX Internet Exchanges. By clicking on a prefix, you get the prefix information dialogue with details (BGP Communities etc.). You can apply further filters, e.g. filter for a specific route server or IX. 

How the different communities can be used

Examples for Mumbai

Please note: In the following examples we only make use of Extended and Large Communities when it becomes necessary.

BGP announcements marked with the following communities are only re-distributed to AS64501 and AS64502 (both 2 Byte ASNs)

  • (0:59200)

  • (59200:64501)

  • (59200:64502)

BGP announcements marked with the following communities are re-distributed to all peers/ ASNs except AS64501 and AS64502:

  • 0:64501)

  • (0:64502)

  • (59200:59200)

BGP announcements tagged with the following communities are only re-distributed to AS65550 (4 Byte ASN) and AS64501 (2 Byte ASN):

  • (0:59200)

  • (rt:59200:65550) or (59200:1:65550)

  • (59200:64501)

 

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