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IP addressing

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by california dead head 1 view

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We had a power outage. After the power was restored the workstations came back up and had were getting IP addresses according to the ipconfig/all from 192.168.0.1 which is NOT our dhcp server it is our firewall. According the the firewall the DHCP service is off on it. DNS came up 192.168.0.1 as well and I know the firewall can't do DNS. Does anyone know if w2000 workstation and XP will default to 192.168.0.1 for the DHCP and DNS even if they really aren't getting addresses? Ideas? If a computer can't find a DHCP server doesn't it go to 169.xxx.xxx.xxx

9 replies

by curacao_dejavu

if a computer doesn't get a ip indeed if gets a 169 adress.
so there is a machine out there that does provide dhcp services.
I suggest to set a ping to 192.168.0.1 and start shutting down devices till you get the one that is providing the dhcp.
It should be possible to snif the network and receive the mac adress and the netbios name of the dhcp server but I don't know how to do that.

Leopold

by bughunter

My guess would be that Internet Connection Sharing (ICS) is enabled on a machine somewhere in your network. Try doing a tracert command using the 198.168.0.1 address (tracert 192.168.0.1), hopefully you will get a machine name back. If you do then that is the machine that is acting like a DHCP server.

by voldar

So, you said that after the power outage all your lan starts going crazy (firewall providing DHCP etc.) If I were you I'd do the following:
- first of all I'd check the DHCP server - to see if it has the right IP address and then the scopes of the DHCP. If all is okay but still the DHCP seams not to lease IPs to the clients I would shotdown it and then start it again. Then I'd check the computer clients performing a ipconfig /release and then ipconfig /renew - just to see if they really get IP from DHCP service.
- and at last but not least I'd turned off the switches and then switch on ;).

To found the computer name with the IP 192.168.0.1 use ping -a 192.168.0.1. If DNS is up you'd obtain the computer name.

Yes - when a computer is in a network environment and no DHCP server is available, automaticaly it gets the APIPA IP (169.x.x.x).

by reference

Chances are that the power outage wiped out a device on your network that is DHCP Server capable. The power outage probably reset this device back to factory default settings which are DCHP Server enabled. The fact that DNS is also set to 192.168.0.1 makes me believe that it is your firewall, because it would consider itself the the authority for DNS resolution if it were the first and last step between clients and internet. I would try recording all Firewall settings, and doing a hard reset/factory reset, and reconfigure, or slap in another firewall to see it if goes away. The suggestion about pinging 192.168.0.1 and shutting down devices is a sure way to discover which device is doing it, I would start with firewall first, you may get lucky!
BTW ping -t 192.168.0.1 will do a continuous ping.
ping -a 192.168.0.1 will attempt to give back information about the name of the device.
Good Luck!

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