pfSense, Virgin Media, Modem Mode

Posted on Thu 29 December 2016 in pfSense

pfSense, Virgin Media, Modem Mode

I had to make a few changes to pfSense that needed a reboot. The Virgin Media SuperHub throws a little hissy fit when I do this and drops the WAN IP.

A while back I read about this happening. A few posts suggested there was an exact timing needed to re-gain a WAN address. I've found a few things whilst troubleshooting;

You can reset your own connection: Login to my virgin media. I usually do a search for "virgin media service status". On the "every things ok" page. Click the run test button. As far as I can tell this resets your line, the same as a new connection or new modem.

Assigning a static IP to the WAN address and putting the superhub in router mode seems to re-enable internet access. Router mode, 9/10 picks up a WAN address. You'll need to set up any port forwarding on the superhub if you run in router mode. Don't point IP's at the clients, point them to pfSense.

Usual: dynamicIP:port = myreallycoolwebpage.com = internal-IP:port

Superhub - Router Modem

dynamicIP:port = Superhub WAN = pfSense = myreallycoolwebpage.com = internalIP:port

This adds an extra hop and makes administration a nightmare, hence modem mode. It's not ideal, but works.

The key is timing, not an exact science. You need to leave everything to settle a while.

Should you loose you WAN IP address.

Reboot the modem Reboot pfSense Do this one after the other, don't wait for either Do the virgin media service check / run test Wait a while, half hour should do it Reboot modem Reboot pfSense

For context, I did this and a few other things last night. Nothing seemed to work. As a last punt, I switched of pfSense, reset the router completely, waited for it to work in router mode. Left it 20 mins. Put it in Mode. Went to bed. 5 hours later woke up, rebooted superhub rebooted pfSense - all working.

What's happening?

Don't quote me on this but I believe it to be a DHCP REBIND Issue Client one talks to server 1, requests a DHCP address. Issued Client one tries to renew it's lease with server 1, who is down for maintenance Server one is unable to respond, client one keeps requesting a release, increasing the time between requests Client one is effectively stuck, unable to gain a WAN address After a while of failed requests, client one enters the REBIND state and broadcasts for a DHCP address

Now this is where the issue lies.

Server two is supposed to respond with a new lease, but may choose not to. It appears that from Virgin Media's side, either server two doesn't exist, or is choosing not to respond. Rebooting everything and leaving it a while allows the REBIND timer to expire, once this happens it enters the REBIND state automatically. There's another possibility. Your modem has a MAC which is being sent with the initial DHCP request. I have a feeling pfSense's WAN MAC is also. Haven't got to tracing that yet. It may well be that repeated DHCP requests from multiple MACs is causing the REBIND issue.

Cloning the superhub's WAN MAC to the WAN interface on pfSense is supposed to get around this, doesn't appear to work for me.

Seems that once the WAN IP has been lost from pfSense, best thing to do is power down the modem for a while, power it up and reboot pfSense at the same time.