I've got a Redhat 9 machine set up as a NAT on my network. This is connected via ethernet to my NTL Cable Modem. However, one machine in the house does not have a network card so uses the USB connection when it is required.

The problem comes when the cable modem is plugged back into the ethernet again and the IP address of the connection has changed, the ethernet card still has the old one. Although deactivating and reactivating the network card solves the problem is there a way of automatically checking if the ip address has changed (a script that could be Cronned etc).

I know this is not the MAC related problems associated with NTL as is worked with Windows XP using the same machine.

The cable modem is connected to device eth0.

Well, you could cron DHCP...

I would recommend simply getting a NIC for the box that doesn't have one. They aren't that expensive. If you look on pricewatch.com, you can even get an Intel 82559-based NIC (great chipset) for around $20. You can get shoddy (like rl8139) cards for much less, probably less than $10 with tax and shipping.

Are you running dhcpcd or dhclient? I don't remember what redhat defaults to.

I'm using DHCPD. The only modifications i've made to /etc/dhcpd.conf are to assign addresses to the pc's on the network.

Yeah, but I thought your problems were with the NAT box pulling a new IP addr when you hooked it back up to the cable modem. This doesn't have anything to do dhcpd on your NAT box. You need to configure your dhclient or dhcpcd. You need to let us know which of these you are running. just ps -aux | grep eth0 and you should see one of these two attached to an interface.

Justin

Sorry, got my wires crossed a bit there.

[root@localhost root]# ps -aux | grep eth0
root 4210 0.0 0.0 0 0 ? SW 21:13 0:00 [eth0]
root 4258 0.0 0.1 1896 948 ? S 21:13 0:00 /sbin/dhclient -1 -q
-lf /var/lib/dhcp/dhclient-eth0.leases -pf /var/run/dhclient-eth0.pid -cf /etc/dhc
lient-eth0.conf eth0
root 4317 0.0 0.1 3508 616 pts/0 S 21:16 0:00 grep eth0


Assume the settings go into "/etc/dhclient-eth0.conf" ?

Yes! You need to man this file and play around with the settings or just modify the ones already there.