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Unauthorized DHCP server on my neighborhood's Layer 2 branch
Cross posted from Customer Support. I have a solution to my specific problem that I'd like to make available to others that may be in a similar situation.
I had been having a problem where every few days I'd lose Internet connectivity for up to 15 minutes, but I could speed up recovery by logging into my router and forcing a DHCP release/renew. About 2 weeks ago while doing this, I noticed that my WAN address was on the 192.168.100.0/24 subnet. Unfortunately I did not catch the IP of the DHCP server.
To resolve my issue I added a line to my router's dhclient.conf file:
reject 192.168.0.0/16;
Ideally the rogue DHCP server should be located and corrected, but that would require action from Comcast. I believe someone just misconfigured their router and set DHCP on the wrong port. It's most likely another customer, so there's nothing I can do about it. All I can do is block DHCP offers from the rogue.
Reference pages for adding the "reject" line to dhclient.conf
https://askubuntu.com/questions/482684/is-there-a-way-to-refuse-a-dhcp-response-from-a-specific-ip
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