Can a router change its own external IP by itself?

I'm using radmin to remotely connect to a certain PC inside a network from my house. The router DHCP is off so I can forward to an specific internal IP (192.168.1.100) for the PC I want to connect . Everything was set and worked correctly and I even enabled the remote administration for the router so I could set it up from my house with a password etc. That used to work well too. But suddenly I can't connect anymore to the router and/or the PC. It seems that the router changed its external IP by itself or something. This is something I'm doing for a client and he says that this happened before and that he called his ISP and they said they haven't changed the IP. The router is a Linksys but I can't say right now what is the model. If anybody coul help me I would really really appreciate it.

Ok I find very interesting "Someoneelse" and "dansinger61" answers if you guys could come to a consensus taht would be great or at least be aware of what each other is saying and may be post a comment?

Thank you all

Typically a router will renew it's IP connection at a pre-determined time period.

It varies from Router to router,.

It's not common for a router to release an ip and then renew.

Your client can pay more to have a Static IP address that way it WILL always be the same.

Perhaps you had a power failure or the ISP had a service interruption that caused your IP number to change.

Usually this would require a long enough outage that your number was assigned to someone else.


Good luck.

What ISP is it? Most are setup with Dynamic IP addresses, or in the case of a cable provider, the IPs lease time may be something like 7 days. I know its set like this for Comcast for example.

Just to be clear here:

You are attempting to connect to a remote machine over the Internet through a router.

Please make sure:
a) The remote machine has connectivity and
b) They have verified the IP at http://whatismyipaddress.com/

Yes. IPS's can sometimes change the IP of your gateway. Use http://www.whatsmyip.org/ to find out what your new IP is.

Yes if you ISP assigns a dynamic IP address ( means it is likely to change with each new connection)

The question really relates to how the router is connected to the internet. If it is through a cable modem, then that device is responsible for obtaining an IP address from the ISP, and any device behind the modem (such as a router) should be using DHCP to maintain a valid connection to the modem. If you disable DHCP in the router, then the router probably disconnected from the modem when the modem renegotiated its IP address with the ISP.