Problems configuring gateway/firewall with static IP addresses

[Matt Singerman]

Hi everyone,

First off, I apologize if I am slightly incoherent, as thi problem has 
been driving me nuts for days now.

I have used Linux before, and have even configured basic network 
settings, but I have never set up a machine as a gateway/firewall.  I am 
now attempting to do this, but I am running into all sorts of problems.

The gateway will be replacing an existing one which is beginning to show 
its age.  It has static IP addresses for both the LAN and WAN, and the 
machines behind it (servers) have publically-addressable static IP 
addresses (not 10.x.x.x, 192.168.x.x, etc.).  This is important, obviously.

I have found numerous guides online for setting up a gateway and 
firewall using DHCP and NAT to use private IP ranges for machines on the 
LAN, but this is obviously not what I want to do.  I cannot find any 
information about setting it up using all static IP addresses.  I would 
assume that this would be if anything simpler to configure, but I am 
havind a devil of a time.

Our local subnet is the entire 141.161.111.0/24 block 
(141.161.111.0-141.161.111.255).  I have a working router on 
141.161.111.241, and the subnet mask being used by all machines here is 
255.255.255.0

Basically, I have eth0 configured to be the WAN connection, and it is 
working fine.  I can ping machines off the network, and machines can 
ping it.  Where I am running into problems is with IP forwarding 
actually allowing connections through.

Here is eth0's config file:

DEVICE=eth0
ONBOOT=yes
BOOTPROTO=static
IPADDR=141.161.111.243
GATEWAY=141.161.111.241
NETMASK=255.255.255.0
NETWORK=141.161.111.0

eth1 is configured to be the LAN interface.  It has the following settings:

DEVICE=eth1
BOOTPROTO=static
BROADCAST=141.161.111.255
HWADDR=00:0E:2E:79:F6:17
IPADDR=141.161.111.242
GATEWAY=141.161.111.242
NETMASK=255.255.255.0
NETWORK=141.161.111.0
ONBOOT=yes

I have modified /etc/sysctl.conf so that net.ipv4.ip_forward is set to 1.

Other than that...  I am at a loss as to what to do.  Can anyone point 
me in the direction as to what my next step should be?

Thanks!