4Byte to 2Byte ASN conversion issue for BGP community

[nitesh058]

Please help for "4Byte to 2Byte ASN conversion issue for BGP community" or share any configuration example.

[pierky]

Mind elaborating a bit? With no extra context I’d say the solution is http://largebgpcommunities.net/

Examples and docs can be found on this GitHub repository or at https://arouteserver.readthedocs.io/en/latest/

[nitesh058]

Hi Pierky, Please help for N:M filtering based on standard community strings. As standard BGP communities support only 4 bytes, How we map peer asn with 2-byte private ASN as per below-mentioned table in arouteserver, so that we can provide a 2-byte private ASN to our other Peers to apply community accordingly.

Peer	32-bit ASN	BGP Community
Peer1	133469	65000
Peer2	132570	65001
Peer3	133168	65002

Please give the solution and thanks in advance..

[lukastribus]

MINAP offers such a mapping with IXP Manager:

https://manager.minap.it/public-content/rs

Mapping 32 bit ASNs

Peers with 32 bit ASNs can be filtered either by using large BGP communities, or by using standard communities and mapping the 32 bit peers ASN to a 16 bit ASN. E.g. routes to AS 201333 can be blocked by tagging them with the 43369:0:201333 large community or the 0:65040 standard community.

[pierky]

Hello @nitesh058,

thanks for elaborating more on your original comment. At the moment ARouteServer does not offer a 32-to-16 bit ASNs map, so filters and other functionalities which are usually offered via std BGP communities are not available for 32bit ASNs. Extended communities and large communities can be used at the moment.

I'll take this as a feature request. I'll update this ticket with any potential plan to implement them.

Thanks again

[pierky]

Hi @nitesh058,

I've just pushed an updated dev branch that contains the new feature.

With the new branch, an alpha release (v1.20.0-alpha1) will come out soon (in about 1 hour, assuming CI/CD will work as expected) and will be available to be installed following the instructions at https://arouteserver.readthedocs.io/en/latest/INSTALLATION.html#development-and-pre-release-versions.

Details about the new release can be already found in the preliminary "dev" version of the docs, at this URL: https://arouteserver.readthedocs.io/en/dev/CONFIG.html#mapping-of-32bit-asns-to-16bit-asns

Later (or max tomorrow) I'll check if everything went well with the release process for this alpha version.

Please let me know your thoughts and share you're feedback if you'll be able to test it.

Thanks

[pierky]

1.20.0a1 is out on the test instance of PyPi: https://test.pypi.org/project/arouteserver/1.20.0a1/

[pierky]

Hi @nitesh058, did you get a chance to look at the solution I've proposed above? Any feedback?

[pierky]

Feature released, no feedback from requestor. Closing this. Feel free to re-open if needed.

[nitesh058]

Hi @nitesh058, did you get a chance to look at the solution I've proposed above? Any feedback?

Sorry to reply on this late, Its working as expected.