AS0 in AS path

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1

hi nanog,

Does anybody have\had experience with BGP announces containing AS 0 in AS path?
I know that AS 0 is reserved by IANA, but still, is it possible to receive such announce messages?

Thanks.

2

eBGP or iBGP? What type of device and/or software are you using to
speak BGP?

As far as I know, most devices should NOT let you set your ASN to 0 or
let you add it to the AS path.

My guess is it's probably going to be filtered by the BGP scanner, but I
don't have any gear laying around that I can play with at the moment to
confirm. :slight_smile:

3

After 3 decades in this business, I can make two predictions:

1) Somebody has managed to fat-finger something and announced AS0 at some point.

2) At least one vendor's gear promptly committed seppuku *after* passing the
broken announcement on to its neighbors.

4

Those aren't predictions, they're statistically certain observations. :slight_smile:

Regards,
-drc

5

Thanks everyone.

Answer is simple - 4byte ASN's.
I was parsing Route Views RIB-IN tables, and found that, by default, Quagga is using 4byte AS length field to store 2-byte and 4-byte AS Numbers.
So, using 2 bytes length in parser, I had wierd output like "0 3549 0 1239" and so on.