Strange speed problems with ipv6 forwarding

[Matt Rowley]

> I got one step further. tracerout shows that route from inside (A)
> outside (B) is A->F->B with F being my firewall.
> 
> But route from B to A goes through the router. I've setup all hosts
> in the subnet in front of the firewall to route their packets through
> the router R that our data center configured for this subnet.
> 
> Thus it's B->R->F->A. The same happens for ipv4, no ->R-> when
> sending from A to B, but via R from B to A. While it's fast for
> ipv4, it's slow for ipv6. So I added a route for the internal
> subnet to the routing table of B so that the trace now shows
> B->F->A. And then the copying between A and B is at full speed
> of 112MB/s.

Hi Frank,

So, R, B, and F all have legs on a common network segment, right?  And B
probably points to R for default gateway?  Does B have routes in its
table so that it knows to point to F in order to reach B?  If not, it is
sending packets to R, who is probably returning ICMP redirects to B.
Perhaps B is dropping them?  A tcpdump on R, B, and F might help show
you what's going on.

--Matt