Having issues getting public IP on WAN interface

[bobbythomas]

Hi Team,

Hope everyone enjoying the holidays.

Well it seems like my holidays are going from bad to worse. Coming to the point I have an OPNsense firewall setup in a VM in Proxmox and it has been working great, couple of weeks back my ISP replaced my Docsis 3 ethernet cable modem with a wifi one, since then I was facing issues. I have disabled the wifi on the new Wifi Docsis modem and configured Bridge mode (as I need public IP terminating on my OPNsense firewall). I got public ip on the modem for some time then it started causing issues, I started getting IP address from 192.168.5.0/24 range even though I have disabled DHCP service on the wifi modem. What ever I do, I only receive an IP address from the range 192.168.5.0/24 on my OPNsense firewall, while if I connect a PC to the modem I am hetting a public IP issued by ISP DHCP server. I am scratching my head to understand why it's happening like this.

I also tried a different approach by assigning the MAC address of the PC to the OPNsense WAN interface and then it gets the public IP but it cannot communicate with anything in WAN (cannot ping gateway or it seems no traffic passing through). Any idea how I can get this issue fixed? I think there is some issue with OPNsense DHCP client service.

Thanks in advance,
Regards,
Bobby Thomas

[MBfromOK]

Just another ProxMox + OPNSense + DOCSIS user here...

I have had this issue as well, still looking for a long term solution.

The most productive settings I have found so far:

• Uncheck the "Block private networks" box for the WAN Interface (DOCSIS -> OPNSense WAN).  The surface level symptoms I have seen make me think there might be a bug involved where it either fails to detect valid IP addresses (www.xxx.yyy.zzz) or times out.
• Check IPv6: Many service providers have begun to standup IPv6 connectivity but routing is not correctly configured, when I stopped allowing IPv6 to be used by services most of my issues with the DOCSIS went away.

[MBfromOK]

I think there is some issue with OPNsense DHCP client service.

I agree with this sentiment, although I have yet to figure out what to change to resolve that issue... Again, it seems to be a routing / translation issue.

[bobbythomas]

No, it's not related to routing or NAT, as soon as I change the modem from bridge mode to routed mode I get the private IP from the modem. As for the "Block private networks", it's already unchecked. My ISP doesn't provide IPv6 addresses yet, so it's not related to IPv6.

I think this is something related to DHCP client service or some configuration on the ISP side which restricts IP allocation to certain MAC addresses (like some virtual mac addresses which has unknown OUI).