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wrt54g + alchemy: my internet interface gets a private ip!

Discussion in 'Cisco/Linksys Wireless Routers' started by pifou, Dec 3, 2005.

  1. pifou

    pifou Guest

    My router has been working for weeks, but some strange things started to happen. This week, the router, which serves as a dhcp server for the internal subnet, and as a dhcp client for the cable modem, got this ip from the modem: 192.168.100.30.

    But the IP should have been a public IP

    I've never used this kind of range, never, my highest subnet was 192.168.17.0/24. I have no idea how the router could have received this IP. The external interface is connected to the modem....there is absolutely nothing special in the config. THere is a WDS, which is working perfectly (192.168.1.0/24) and 3 machines connected to the internal switch. After restarting the router, the IP was correctly detected by the dhcp client, a public IP.

    I've called the ISP, they have no idea and told me to call them as soon as it happens again.

    Is there a 192.168.100.0/24 range hard coded in the router ? Someone have an idea ?

    Note: the other problems I was talking bout could have been cause d by electrical problems (short glitch on the AC power, maybe).

    I'm thinking about 3 possibilities:

    1) hacking (via wireless, but the WDS is protected by WPA and a strong password, but the admin pass was default :shame)
    2) electrical problems: The house could have problems caused by very old wires.
    3) ISP problem: They are migrating many customers to a new platform and are sending new cable modems to replace older models.
     
  2. Guyfromhe

    Guyfromhe Network Guru Member

    What kind of modem do you have?
    many cable modems use the range of 192.168.100.0/24 for troubleshooting, if the modem isn't locked at the the when an IP is requested via DHCP the modem will return an ip in that subnet so you can connect to it's webserver/telnet server if it has one. if it's a Motorola Surfboard this is probably what it is, you can try to reproduce it by doing this:
    1) Unplug the coax from the modem.
    2) unplug and then reconnect the modem
    3) unplug and reset the router
    4) see if it's WAN ip is in the 192.168.100.0/24 subnet
    if it is then thats what the problem was, it requested an ip when the modem fell offline for whatever reason... you can then check the default gateway and try to browse to it and you should see the modems diagnostic page.
     

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