Hello, all. I am trying to set Redhat Linux 9.0 up as a gateway for my testbed network. Right now, the setup is like this:
Cable Modem---Lynksys Router/Firewall---Linux Machine---TestNet
###########################|_____________|
With the direct link between the Lynksys and the Testbed Network (marked with #), everything works fine. Linux and the testbed can access the internet. However, when I remove the link, I can no longer get Linux to access the internet. But it can still ping the Lynksys at 192.168.1.1. What is wrong??

Eric S.
PS: I'm sorry if this is the second time I posted this. My first totally disappeared.

It sounds like a routing problem. What do you get if you do:
route -n
ifconfig

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth1


eth0 Link encap:Ethernet HWaddr 00:10:B5:9E:86:4E
inet addr:192.168.1.105 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:63482 errors:0 dropped:0 overruns:0 frame:0
TX packets:31850 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:6050061 (5.7 Mb) TX bytes:1951231 (1.8 Mb)
Interrupt:11 Base address:0xb000

eth1 Link encap:Ethernet HWaddr 00:08:C7:08:F4:C4
inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:44339 errors:0 dropped:0 overruns:0 frame:0
TX packets:11185 errors:2 dropped:0 overruns:0 carrier:2
collisions:101 txqueuelen:100
RX bytes:11415672 (10.8 Mb) TX bytes:1310608 (1.2 Mb)
Interrupt:11 Base address:0x2400 Memory:40300000-40300038

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:1692378 errors:0 dropped:0 overruns:0 frame:0
TX packets:1692378 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:109714694 (104.6 Mb) TX bytes:109714694 (104.6 Mb)

If you are going to have a LAN and a WAN side to your gateway then use 2 different subnets. Your routing will just get confused if not.

I will soon connect directly to a cable modem, so I will have a public IP address. How can I fix the problem for now? If I wanted to use 10.1.x.x for my subnet, what would my netmask be? 255.255.0.0? How do I set this up???

yes - and that is hoe you would set it up. Just change the ip info on the lan side and eth0.

Make sure eth1 is plugged into the linksys

eth0 is externel and eth1 is internel. Now I have an even stranger problem. I can ping the IP address for yahoo.com. I can even port scan it with nmap. However, I can't resolve the domain and, even stranger, I can't get to the website, even when I type in it's IP address. The internel network and the Lynksys network work fine. However, I can make it work okay. I just have to turn my firewall off. Maybe it is a problem with not allowing fragments by accident?? I'll try to mess around with it.

I fixed this problem by telling iptables to accept packets that are RELATED or ESTABLISHED and to accept fragments. Thanks for all your help!

how do i do this?