Router resets its IP address.?

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Mar 11th, 2008
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In a doctor's surgery there was a LAN comprising of an ADSL modem + D-Link Router + several PCs.

I replaced the ADSL modem + D-Link Router with a new 877w Cisco Router (which has an in-built ADSL modem). The cisco router is DHCP enabled - ie, is a DHCP server.

The original D-Link Router's IP address was and as it was a DHCP server all the PCs were automatically give a 192.168.1.x address.

The factory default address of the Cisco Router was Using this address I accessed the router's HTML configuration pages and changed the Cisco Router's IP address to:

Then I restarted all the PCs and verified that they had IP addresses in the range -

However, every time I re-visit the surgery, all the PCs have reverted to 10.10.10.x addresses and the router has gone back to being

Can anyone tell me why this is happening and how to permanently change the Cisco Routers IP address to

Many thanks, James

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lamav Tue, 03/11/2008 - 18:54
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Did you save the config after you changed the IP address scheme with the web interface?

jzelliott Tue, 03/11/2008 - 20:37
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Good question ... I am sure I saved the configuration, but cannot swear to it. The router operated with IP address all the time I was on the premises, and all the PCs had IP addresses in the same range when they were restarted, so I think I must have saved the configuration ... or, can an unsaved configuration persist until the PCs are restarted on another day, or, perhaps, until the router expereinces a power failure (the router is not yet on a UPS)?

Many thanks for your interest and contribution. I wonder if anyone else has any other ideas?

Thanks, James

Hi James

As alluded to by the previouus poster, if you have not saved the configuration, then the router will work perfectly well on 192.168.1.x and provide these IP addresses via DHCP, up until the router is power cycled. At this point in time it will revert back to it's original configuratin of 10.10.10.x.

This might explain why the router is working fine while you are there. It's possible that maybe the cleaners etc temporarily unplug the router for some reason which causes it to revert back to the original configuration.

Best Regards,


lamav Wed, 03/12/2008 - 09:59
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Michael is exactly right.

Its not a matter of rebooting your PCs or not. Its a matter of rebooting the router. The router is acting as the DHCP server, not the PCs.

Change the router setting to what you want and save it on the router.



jzelliott Thu, 03/13/2008 - 01:30
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Thank you Michael and Victor ...

I am sure you are right - I must have forgotten to save the new IP address. Being in a rural area the power does go off from time to time and that is probably the explanation for the router reverting to factory default IP settings.

Many thank, James

Hi James

It could be that you have saved the configuration and the power outage is causing the problem.

I had an issue a couple of weeks back. Granted the switch involved was not a Cisco and it was a few years old. However the building suffered a power outage over the weekend and the switch is in a lab do no UPS.

Anyway, while I was checking the network, I noticed that I could not connect to any devices off of this switch. When I logged onto the switch, it had reverted back to "out of the box" condition. It had no configuration at all.

These thing happen, though thankfully not that often :)

Best Regards,



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