Re: [LARTC] Routing problem (RTNETLINK answers: Invalid argument) on

[Alex Samad <alex@samad.com.au>]

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On Wed, Feb 14, 2007 at 08:30:48AM +0100, Paul Viney wrote:
> > > I still seem to have much the same problem. I no longer get ICMP
> > > unreachable errors, but the packet just seems to disappear - I can't see
> > > it being forwarded on any interface, nor can I find any kind of reply -
> > > icmp or otherwise.
> >
> > sounds like a firewall issue!
> 
> It does sound like a firewall issue, but the only firewall rule I have at the 
> moment is the one doing the DNAT. If I do 'iptables -t nat -L -v', then I can 
> see the number of packets increasing. Once I remove the firewall rule, I get 
> my "icmp unreachable" errors again. Funnily enough, if I then reinstate the 
> firewall (dnat) rule, then I still get "icmp unreachable" errors and the 
> packet count doesn't go up for the rule. It's almost as though the rule 
> doesn't get consulted. 'ip route flush cache' doesn't make a difference. 
> After about 5 minutes the "icmp unreachable" errors stop and the packet count 
> starts going up, although I still can't find my packet on the next hop. (I do 
> have forwarding switched on). The packet count on a iptables log rule on the 
> forward table does not go up, giving me the impression that routing has 
> failed. 

This could be connection tracking, once you start a ping, connection tracking
will keep it in its cache, so even though you have placed it (the rule) back in
it doesn't count for the established link...

> I also tried ip r get <random internet address> from 192.168.12.5, which did 
> indeed give me the same "RTNETLINK answers: Invalid argument" error. I guess 
> that means that my understanding of the purpose of 'ip r get' is indeed 
> faulty. 

does 192.168.12.5 exist on your box, can up do an ip a
also do you have forwarding on ?

> 
> Thanks for all your help so far.
> 
> Paul Viney
> 
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