maximum ipv4 bgp prefix length of /24 ?

Dale W. Carder dwcarder at
Wed Oct 11 18:50:40 UTC 2023

Thus spake via NANOG (nanog at on Tue, Oct 10, 2023 at 04:52:07PM -0700:
> However, IF YY is paying attention, and YY wants to advertise 2001:db8::/32 as well as allow 2001:db8:8000::/36 and 2001:db8:f000::/36, I would expect AS YY would generate ROAs for
> 	2001:db8::/32 with ORIGIN-AS=YY MAXPREFIXLEN=36
> 	2001:db8:0::/33 with ORIGIN-AS=0 (no MAXPREFIXLEN needed)
> 	2001:db8:8000::/36 with ORIGIN-AS=YY MAXPREFIXLEN=36
> 	2001:db8:9000::/35 with ORIGIN-AS=0 (no MAXPREFIXLEN needed)
> 	2001:db8:a000::/34 with ORIGIN-AS=0 (no MAXPREFIXLEN needed)
> 	2001:db8:c000::/34 with ORIGIN-AS=0 (no MAXPREFIXLEN needed)
> 	2001:db8:e000::/36 with ORIGIN-AS=0 (no MAXPREFIXLEN needed)
> 	2001:db8:f000::/36 with ORIGIN-AS=YY MAXPREFIXLEN=36

Double check, but offhand I believe in this case you do not need all 
these AS0 ROA's.  Any validated ROA payload fully matching should be
all you need for it to be valid, and anything that is covered by a vrp
but not matching is invalid.

So, I think you can do
 	2001:db8::/32 with ORIGIN-AS=YY MAXPREFIXLEN=32
 	2001:db8:8000::/36 with ORIGIN-AS=YY MAXPREFIXLEN=36
 	2001:db8:f000::/36 with ORIGIN-AS=YY MAXPREFIXLEN=36


More information about the NANOG mailing list