I need to access a Linux box via SSH & Samba that is hidden/connected behind another one.

Setup :-

  
 A        switch    B         C
|----|    |---|    |----|    |----|
|eth0|----|   |----|eth0|    |    |
|----|    |---|    |eth1|----|eth1|
                   |----|    |----|

Eg, SSH/Samba from A to C

How does one go about this?
I was thinking that it cannot be done via IP alone? Or can it?

Could B say "hi on eth0, if your looking for 192.168.0.2, its here on eth1"?
Is this NAT? This is a large private network, so what about if another PC has that IP?!

More likely it would be PAT?
A would say "hi 192.168.109.15:1234"
B would say "hi on eth0, traffic for port 1234 goes on here eth1"
How could that be done?

And would the SSH/Samba demons see the correct packet header info and work??

IP info :-

A - eth0 - 192.168.109.2
B - eth0 - B1 = 192.168.109.15 B2 = 172.24.40.130
  - eth1 - 192.168.0.1
C - eth1 - 192.168.0.2

A, B & C are RHEL (RedHat) But Windows computers can be connected to the switch. I configured the 192.168.0.* IPs, they are changeable.

Update after response from Eddie

Few problems (and Machines' B IP is different!)

From A :-
ssh 172.24.40.130 works ok, (can get to B2)
but ssh 172.24.40.130 -p 2022 -vv times out with :-

OpenSSH_4.3p2, OpenSSL 0.9.8e-fips-rhel5 01 Jul 2008
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to 172.24.40.130 [172.24.40.130] port 2022.
...wait ages...
debug1: connect to address 172.24.40.130 port 2022: Connection timed out
ssh: connect to host 172.24.40.130 port 2022: Connection timed out

From B2 :-

$ service iptables status
Table: filter
Chain INPUT (policy ACCEPT)
num  target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
num  target     prot opt source               destination
1    ACCEPT     tcp  --  0.0.0.0/0            192.168.0.2         tcp dpt:22

Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination

Table: nat
Chain PREROUTING (policy ACCEPT)
num  target     prot opt source               destination
1    DNAT       tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:2022 to:192.168.0.2:22

Chain POSTROUTING (policy ACCEPT)
num  target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination

And ssh from B2 to C works fine :-

$ ssh 192.168.0.2

Route info :-

$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0     *               255.255.255.0   U     0      0        0 eth1
172.24.40.0     *               255.255.255.0   U     0      0        0 eth0
169.254.0.0     *               255.255.0.0     U     0      0        0 eth1
default         172.24.40.1     0.0.0.0         UG    0      0        0 eth0

$ ip route  
192.168.0.0/24 dev eth1  proto kernel  scope link  src 192.168.0.1
172.24.40.0/24 dev eth0  proto kernel  scope link  src 172.24.40.130
169.254.0.0/16 dev eth1  scope link
default via 172.24.40.1 dev eth0

So I just dont know why the port forward doesnt work from A to B2?