I am connected to the internet via cable modem. I have a 4 port router plugged into the cable modem. I have 2 linux PCs connected to the the router. They are networked together and both have internet access. I would like to set static IP addresses on both linux boxes so that I do not have to change /etc/hosts when DHCP changes their IP.

question
Is this possible set static IPs with the network I have? My cable modem is from Cablevision Optium online and does not have a static ip. Do I need a static IP address from the cable company to set static IPs on my linux boxes.

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linux box 1
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computer os: centos 5.7 64-bit
hostname: server.localdomain
current ip eth0: 192.168.1.6 -> This changes alot, I would like to convert to static
default gateway: 192.168.1.1

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linux box 2
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computer os: centos 5.7 64-bit
hostname: laptop.localdomain
current ip eth0: 192.168.1.4 -> This changes a lot , I would like to convert to static
default gateway: 192.168.1.1