3 computer network - how to???

[ubu-user]

Hi all,
What I was trying to do on my own but found many difficulties, since I'm not really experienced on this field, is the following:

On 3 virtual computers (A is ubuntu, B is fedora and C is debian Lenny) I'm trying to make some connections between them.
More specifically:

A connection between A and B through an SSH tunel. In this tunel, A has IP 172.16.1.1/24 and B172.16.1.2/24
A connection between B and C through an SSH tunel, B with IP 172.16.2.2/24 and C 172.16.2.3/24
I need to activate the rooting (but without NAT) on computer B with this command:

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

And then I thought that by doing a ping between each PC just to check that they communicate with each other.
I found many information in the internet, however I just couldn't make this work. Do you have any other links that could help me, or could you give me some pointers on what commands should i use to achive that?

I would be very grateful for any help you can provide.

[Sasquatch]

You've done only half of it. The ip_forward is the first step, the second is to use iptables to actually do the forwarding. I'm guessing that all three VMs can ping the required machine(s)? So A can ping B, B can ping both A and C and C can ping B.