External Network Change

[Patrick Nelson]

FC3 (all up to date)

This may seem simple but I'm changing ISPs and I have 2 internet facing 
systems that also connect to the private network.  One being the GW the 
other being Mail.  So I have the gateway working fine but I can not get 
the mail server working in the changed network config.  I just want to 
make sure I'm not missing anything, because I think that the ISP is not 
routing, switching, or configured correctly.

-The two systems are attached to a Hub along with the connection to the 
Internet.
-The gateway system is working fine with the new ISP changes (serves as 
the DNS and GW)
-The mail server can be configured with the new ISP, but once I do that 
system can not ping the internet
--however it can ping the internet side of the GW
--and the intranet.
-With ethereal I sniffed the mail server connection and it does appear 
to get anthing back from the ISP GW

Here are the changes that I make to mail server:

1. Use system-config-network to change the:
 -IP Address
 -Subnet Mask
 -Gateway
2. Change the IPTables Firewall Script to match the new config
3. Turn off the firewall script for the first booting in the new network 
config
4. Reboot

The booting goes fine but I can not ping anything other than the GW 
system on the Internet side.

Is there anything that I'm missing or might try?  Or does this sound 
like a routing problem on the side of my ISP?