[afnog] 32 bit ASN

[Geert Jan de Groot]

On Tue, 25 Jan 2011 00:51:11 -0600 a.onuche at nixp.net wrote:
> We applied for an ASN number from Africnic and was given a 32bit ASN number.
> To my dismay,Our equipment rejected the ASN number,
> How do i implement a 32 bit ASN on older equipment?
> What are the options and the best way possible round this?

The depletion of the 16-bit ASN space, and the introduction of 32-bit
ASN numbers, has been going on for a number of years now.
The policy defining the transition mechanism AFPUB-2005-ASN-001,
has been around for more than 5 years now.

You will need to upgrade the IOS on your BGP speaker if it does not
understand 32-bit ASNs. I'm sure others (tinka?) can tell what
version to use - I'm not versed in IOS releases.

Your peers do not need to upgrade, though upgrading is advisable.
To non-32-bit capable BGP speakers, you will look like AS 23456.
That works, and works well, except that all 32-bit ASN speakers
will look like AS23456 and hence the peer cannot set policy based
on AS path.

We demonstrated that 32-bit ASNs do work at the 2009 AfNOG meeting,
where the event network was announced from AS327685.

There is good reading on this topic. See, for instance,
- http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_9-1/autonomous_system_numbers.html
- http://www.ripe.net/info/faq/rs/asn32.html

Note that there are various different ways to write down 32-bits ASN numbers,
like AS327685, AS5.5. Consensus is to use the first format (see RFC5396), 
though you may see other formats in older documentation or in 
some early implementations.

Hope this helps,

Geert Jan