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Re: packet forwarding.



On Sat, Aug 02, 2008 at 10:18:17PM -0700, Mike Bird wrote:
> On Sat August 2 2008 18:31:40 peasthope@shaw.ca wrote:
> > My network is illustrated here now.
> > http://carnot.pathology.ubc.ca/Network.jpg

[snip]

> > "no connection".
> 
> That routing table shows that dalton knows the route to joule.
> From the network diagram we see that dalton also knows the
> (connected) route to cantor via eth3 (aka eth1).  Assuming no
> iptables blocks on any of the three systems, you still need to
> ensure:
> 
> 1) That cantor knows the route to joule (via dalton)
> 2) That joule knows the route to cantor (via dalton)
> 
> In short, every step along the way needs to know how to route
> packets in both directions.

something you can do to help track it down is start a ping from cantor
to joule and use tcpdump at each of the hop and do a 

tcpdump -pni <in interface> icmp and host cantor -c 10

and then a

tcpdump -pni <out interface> icmp and host cantor -c 10

Trace the packet all the way.

on cantor you can start of with 

ip r g <ip address of joule - note ip r g doesn't take hostname :( >

once you know the next hop then you can ssh to there and do the tcpdump
thing

Alex

> 
> --Mike Bird
> 
> 
> --
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-- 
Miksch's Law:
	If a string has one end, then it has another end.

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