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Re: Problem with multiple ethernet interfaces



Mostafa wrote:
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
> 10.5.5.0        0.0.0.0         255.255.255.0   U     0      0        0 eth1
> 192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
> 0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 eth0

Looks good.

> I have two subnets connected to two ethernet interfaces of a cisco router
> 192.168.1.0/24 and 10.5.5.0/24.
> 
> The problem that I have is that, I cannot access the 192.168.1.20
> interface from the 10.5.5.0/24 subnet. Also, I cannot access the 10.5.5.20
> interface from the 192.168.1.0/24 subnet. However, all machines in the
> 10.5.5.0/24 subnet can access the IP 10.5.5.20 and all machines in the
> 192.168.1.0/24 subnet can access the IP 192.168.1.20.

I think one would expect your router to transport packets across the
intranet to the other interface.  Perhaps I did not understand but
your two subnets are connected how?

Are you expecting this machine to be simply dual homed with two IP
addresses, one on each subnet?  Or are you expecting it to become a
router and to route packets itself from one interface to another?

If you want a machine with multiple interface cards to become a router
then you will need to enable packet forwarding in the linux kernel.

  echo 1 > /proc/sys/net/ipv4/ip_forward

Bob

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