i got assigned a different ipaddress. i'd like the old one i had. my router/firewall does not have a way to assign an ip via the mac address. i tried editing the address in dhclient-eth0.leases but when i restart the network, it goes back to the old address. how do i assign the old ip address i had?

To solve this problem, you can use static ip address
copy all the settings from dhcp configured eth0 except your ip(mainly gateway,subnet mask, DNS 1 & 2)
now configure the eth0 as static with all those settings and the ip address you want.
Normally only the last part of ip address can be configured, first three parts have to remain the same as assigned by dhcp
if aaa.bbb.ccc.ddd is the ip you can change ddd only from 0-255 excluding the number gateway uses.
Normally ip address will be same as gateway for first three parts.
Hope it helps..