IP Spoofing Causing Internet connectivity issues

Posted on 2004-11-03
Last Modified: 2010-04-09
Hello Everyone,

I am experiancing a major problem with my firewall and IP Spoofing.

Last night i changed over our netowrk from a public IP address scheme to a private scheme i.e 66.160..... to 192.168.....
After the change over everything seemed to be runnigns mothly but i had only sampled about 10 of the 45 computers in my office.

today i am getting reports from my SonicWall SOHO2 firewall of IP Spoofing from the internal LAN. The IP address go back to actula workstations some PCs some Macs. All of these "Spoofed" addresses will not connect to the internet, since obveiously the firewall is blocking them from going out to the internet.

I have looked at the SonicWall support site and there really was no helpful tips to resolve the issue. I have double and triple checked the settings via ipconfig and they are all correct to my network.

Any suggestions will be thouroghly welcomed.
Question by:kendingo
    LVL 9

    Accepted Solution

    I do not know SONIC, but other firewalls need to be told of your new IP range forn internal network. These are normally known as Local Address Tables (LAT). Does the Sonic have such a setting for ading IP ranges of your new internal network?

    It could also be a route missing in SONIC. Does it have a route that tells it how to get to your new IP network?

    Just some things to think about. Sorry I don't know Sonic.
    LVL 1

    Author Comment

    Found the problem to be a miss configured subnet mask on the LAN interface. it was only allowing 14 valid hosts. Changed it to the correct setting now everything is super terrific good.

    Thanks for the insight, while not the direct right anser it got me lloking around in the firewall a little deeper.


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