Re: IP forwarding problem

[Matt Zagrabelny <mzagrabe@d.umn.edu>]

On Fri, 2006-01-27 at 14:52 +0000, Oliver Elphick wrote:
> Can anyone help with this network problem, please?
> 
> This machine is an internal router, with two network cards.  iptables is
> not configured in the kernel, since masquerading and filtering is not
> required.  (There is a separate firewall machine.)
> 
> 192.168.2 (eth0) is a network with Windows machines.  Packets to and
> from that network are no longer being forwarded.  The routing table
> appears to be correct and IP forwarding is turned on.

how are you turning forwarding on?

what does:

# sysctl -a | grep forward

list?

ie:

# sysctl -a | grep forward
net.ipv4.conf.eth1.mc_forwarding = 0
net.ipv4.conf.eth1.forwarding = 1
net.ipv4.conf.eth0.mc_forwarding = 0
net.ipv4.conf.eth0.forwarding = 1
net.ipv4.conf.lo.mc_forwarding = 0
net.ipv4.conf.lo.forwarding = 1
net.ipv4.conf.default.mc_forwarding = 0
net.ipv4.conf.default.forwarding = 1
net.ipv4.conf.all.mc_forwarding = 0
net.ipv4.conf.all.forwarding = 1
net.ipv4.ip_forward = 1

> 
> Machines on 192.168.2.* are able to ping 192.168.1.18 (the other network
> card on the routing machine) but they cannot ping any other machine on
> the 192.168.1 network.  Similarly, the router can ping 192.168.2.* but
> no other machine on 192.168.1 can do so.
> 
> This set up was working until it was shut down and rebooted :-(

sometimes after a kernel upgrade or a reboot physical interfaces will be
renamed by the kernel. that will screw things up, but if you can ping
interfaces from the clients that doesnt sound like the problem, just
thought i would mention it.


-matt zagrabelny