IP Address changing

Why do my IP Address's change all by themselves? I have 3
PC's on a home network connected to the Internet. Two
computers run XP one Windows 98. After I set up all three
Fire Walls to Trust the IP Address of the other PC's -
every few weeks the IP Address's change and the network
gets screwed up. Why does this happen? How do I stop it
from happening?

Barry wrote:
Why do my IP Address's change all by themselves? I have 3
PC's on a home network connected to the Internet. Two
computers run XP one Windows 98. After I set up all three
Fire Walls to Trust the IP Address of the other PC's -
every few weeks the IP Address's change and the network
gets screwed up. Why does this happen? How do I stop it
from happening?

It depends on how you have things set up. Are you using a router
to do NAT? When you say your IP addresses are changing, are you
looking at internal or external IP addresses? Are you using DHCP
to assign addresses? Are you getting an Internet address (or more
than one) via PPPoE or some other such protocol?

The short answer is your addresses will change if you are using
DHCP to assign them and the leases are allowed to expire in such a
way that the previously leased address isn't available when sought,
and will change if you are getting them via (e.g.) PPPoE and your
connection drops, allowing your ISP to assign any address it chooses.

You probably shouldn't be relying on IP addresses to configure your
firewall anyway. MAC addresses would be better.

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