[j-nsp] RPF check

[Pekka Savola]

On Wed, 5 May 2004, Anton Schweitzer wrote:
> forwarding-table {
>     unicast-reverse-path feasible-paths;
> }
> 
> and on the interface :
> 
> rpf-check fail-filter count_rpf_fail
> 
> The box is receiving two BGP prefixes from an external AS.
> It is getting a 1.1.1.1/28 over the interface with the rpf check
> enabled and a 1.1.1.1/29 from a BGP peer. As far as i understand
> it should then have a feasible path to 1.1.1.1 over the interface
> where the rpf is enabled. But the rpf check for packets from 1.1.1.1
> coming in from the rpf interface fails....

No, 1.1.1.1/28 is not feasible with respect to 1.1.1.1, it's a more 
specific.

If both advertised the same prefix length, it would be considered 
feasible.

The advertisement have to be consistent.  See RFC3704 section 2.3.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings