Not Getting IP Address from Cable Modem

marksabado · Apr 28, 2024, 1:03 PM

@marksabado Does anyone have a hint as to how I might track this issue down? I still can't use one of our two internet providers because the WAN port is not getting an IP address. However, I can plug a PC into the cable modem and successfully get an IP address. Optimum can also see the MAC address of my WAN port when they connect through the Optimum cable modem as well as the IP address the cable modem is trying to assign to it. pfSense just shows 0.0.0.0.

SteveITS · Apr 28, 2024, 1:03 PM

@marksabado first thing would be to upgrade to 2.7.2. If you’re not seeing it run this command: https://docs.netgate.com/pfsense/en/latest/releases/2-7-1.html#troubleshooting

Have you tried powering off the cable modem?

I recall seeing threads about this but I have never had the issue.

viragomann · Apr 28, 2024, 1:03 PM

@marksabado
Are you sure, that the modem is trying to assign an IP to pfSense?

Check the DHCP log. You can filter it for client entries.

Also you can sniff the DHCP traffic on the WAN. It is plain text, so you can read, what exactly going on there.

Jarhead · Apr 28, 2024, 1:21 PM

@marksabado Another thing to try, the PC that gets an address, spoof it's MAC on the pfSense WAN

marksabado · Apr 28, 2024, 2:47 PM

@SteveITS Thanks, I will try upgrading to 2.7.2. We have been through multiple power cycles of both the cable modem and the router.

marksabado · Apr 28, 2024, 2:54 PM

@viragomann I will try to look at the logs and see if I can get any hints. When I have Optimum on the phone, they can see the MAC address of the router's WAN port. They can also see the DHCP address that has been assigned to the router by the cable modem.

marksabado · Apr 28, 2024, 5:09 PM

@Jarhead I tried all the other suggestions in this thread, but MAC spoofing was the one that worked! I used the MAC address from the machine I tested with the modem and that worked. Does this mean that the ISP is locking on an IP address? If so, why did it take a random machine that I connected to it versus the router that has been connected to the cable modem for years? In any event, I did ask the Optimum technician about this while on the phone, and he claimed that they don't tie to MAC addresses.

Good news, router is now connecting through the ISP. Bad news, will there be a conflict if I place the machine with that actual MAC address back on the network - it is on the LAN side while the router is using this on the WAN port?

SteveITS · Apr 28, 2024, 5:21 PM

@marksabado usually powering off the cable modem releases this. Check if it has a battery in it, some with voice do. Possibly, leave it off for a while?

Dobby_ · Apr 28, 2024, 5:51 PM

..... cable modem.....

Is this a real cable modem or a router?

Normally you install the modem in front of the pfSense and connect
it to the WAN port and at the WAN gateway you select IPv4 & IPv6
DHCP if you are not sorted with an static IP address.

marksabado · Apr 28, 2024, 6:06 PM

@SteveITS Thanks, it has been unplugged multiple times, but only for 15-30 seconds. I don't think there is a battery, but happy to try it for a longer period.

marksabado · Apr 28, 2024, 6:08 PM

@Dobby_ Yes, this is how we are setup. There is not a static IP address, but the cable modem assigns an address to the WAN port on the pfsense router through DHCP. This has been stable for several years before it suddenly stopped working and showed an IP address of 0.0.0.0. Since MAC spoofing solves it, I think the cable modem or ISP is somehow locking the old MAC address and excluding it.