I have three boxes as following :-
1. Box A (eth0: 192.168.1.103)
2. Box B (eth0:192.168.1.100; eth1:192.168.1.101; eth2:192.168.1.102). Eth1 connects to A and Eth2 to C. And Eth0 to the Internet. So box B connects A to C and is connected to the Internet.
3. Box C (eth0: 192.168.1.104)

The set up is like this :-
I am trying to have A communicate with C. So this is what I did :-
1. On A and C, I have the corresponding interface of B as the default gateway.
2. On B, I did a
so that it sends data to A on its eth1 and data to B onto eth2.

Here is the routing table on C:-
Now I can ping from A->B, B->A, C->B and B->C. But NOT from A to C.

I am not sure why because I have made sure that B knows how to route data by setting the static routes. But it's not routing it for some reason. When I run ethereal on B's eth1, I see that it's getting ARP requests from A for C (I tried pinging C from A). But it simply not forwarding it.

Any help will be greatly appreciated.

Thanks,
K

Well, what are netmasks? You obviously have all the boxes in one subnet 192.168.1.* . But if a box in a subnet receives a packet from another box in the subnet for the third box in the same subnet it will think "Ah, we're on hub" and not forward it. Futhermore, ARP requests are never forwarded. You just failed to make A _route_ to C - if A sends ARP (inside-LAN) packets for it. So try again with A-B in 192.168.1.* and A-C in 192.168.2.* .

Hi Ruskin,

Thanks for the note. I tried that but no success

I felt that I could explain the problem better and here it is :-
http://www.linuxquestions.org/questi...65#post2317365


Thanks,
Harsha

------------------------------------------------------
[Box A] <==========> [Box B] <===========> [Box C]
------------------------------------------------------
192.168.1.103<---->192.168.1.101
255.255.255.0 255.255.255.0
eth0 eth1
------------------------------------------------------
192.168.2.1<--------> 192.168.2.2
255.255.255.0 255.255.255.0
eth2 eth0
------------------------------------------------------
192.168.1.100
255.255.255.0
eth0
[to Internet]
------------------------------------------------------


From what i can see you have box B with 2 cards with the same network ID, yet you have box C on a conpletely different class C network, which is good. you should do the same for box A.

Also as a industry standard most admins will put all gateway address to end with 254, this makes it much easier for people to understand the layout of the routes, maybe try something like this:

------------------------------------------------------
[Box A] <==========> [Box B] <===========> [Box C]
------------------------------------------------------
192.168.3.103<---->192.168.3.254
255.255.255.0 255.255.255.0
eth0 eth1
------------------------------------------------------
192.168.2.254<--------> 192.168.2.2
255.255.255.0 255.255.255.0
eth2 eth0
------------------------------------------------------
192.168.1.100
255.255.255.0
eth0
[to Internet]
------------------------------------------------------

Then you may need to turn on ip_forwarding in the kernel to allow the packets to be forwared to the different network cards at the command line type:

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

Thanks for the note fotoguy. I did just what you mentioned and have it working.

Good to hear you have it working.