ISP support for use of 4-byte ASNs in peering

Nick Hilliard nick at
Tue Aug 9 09:24:26 CDT 2011

On 09/08/2011 14:47, John Curran wrote:
>   At ARIN, we are still having parties returning 4-byte ASN's (seeking 2-byte instead),
>   indicating that the 4-byte ones are not sufficiently accepted in peering to be usable.  
>   This is obviously a less than desirable situation, and it appears that it is not trending 
>   towards resolution at this time.

At INEX, we see 60% of IXP connections which can handle ASN32 natively.
However, INEX is a small IXP and I haven't seen similar figures from other
IXPs which could validate this 60/40 split.

Having said that, in the IXP world most new service providers connect into
route servers, so there is often no perceived requirement for direct
ASN32->ASN16 interconnection - the intersection of new service providers
and ASN32 holders is quite large.  And if you really want a bilateral
peering relationship, there's no reason not to use AS23456.

> Thoughts?

- interior BGP community management is great fun with an ASN32, oh yes.

- i don't have much sympathy for people who whine about not being able to
support ASN32 peerings.  There is no good reason for this these days.

- from personal experience, I understand why ASN32 is less popular.
However, it's certainly usable.


More information about the NANOG mailing list