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DHCP Issues

Frequent Visitor

DHCP Issues

I just replaced my cable modem, and only certain devices can get an IP address from the modem. I'm not sure why, but my router I was using no longer can get an IP from the Cable modem. I had to switch back to an older router that I had lying around just to get internet access. When I log into my account, the serial number of my cable modem is listed as the MAC and not the serial. Not sure if the 2 are related. Not sure why certain devices get IP's and other's dont. Tested multiple devices.

Expert

Re: DHCP Issues

Are you power-cycling the modem each and every time that you change the device that is being directly connected to it ?

 

You should call in to customer service and get the MAC addy/ serial number thing straightened out.



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Frequent Visitor

Re: DHCP Issues

Yes I unplug it. I'll get a 192.168.100.20 address temporarily, but never an external IP on those devices.
Expert

Re: DHCP Issues

Try suggestion number two.



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
Frequent Visitor

IPv6

Is IPv6 Required on my router to get an IP address from the comcast DHCP servers. I found out my router does not support getting a IPv6 Address via DHCP and I'm wondering if that might cause my issues for connectivity.

Frequent Visitor

Re: IPv6

I get a 192.168.100.20 address when the cable modem is configuring, but won't get that external IP afterwards. This was working fine with my prior cable modem which was sb6121 I believe, but wont' work with my sb6190 Help @ComcastJohn