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Losing DHCP on router when using bridge mode on bluecurve modem from Shaw

ne0rmatrix
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Good morning from Canada! I'm having issues with my internet connection and was hoping for some advice from all of you at Linus Tech Tips forums. I have internet with Shaw Cable in Canada. My internet connection is 1GB down and 100Mb up.

I have my Bluecurve modem (model is Arris TG3482ER3) in bridge mode. Directly connected to it is a Unifi USG-3P router running firmware 2.4.8. From their it connects directly to a USW-FLEX-Mini smart switch. From their I have multiple branching devices. Directly connected to first switch is my PC which uses a ethernet cable to plug into the switch. Also on same switch is a second identical switch. On the first switch the second device a UCK-G2-Plus (That is a unifi cloud key gen2) which controls the network and sets up the devices and updates firmware etc. The router has no custom configuration and has dhcp for both WAN and LAN on default. As configured IPV6 is disabled as it requires custom configuration and I had reset router and not done anything beyond set up wifi. I had a sweet custom configuration with separate VLANS for IOT devices etc but turned that all off for ease of testing out this problem.

Randomly the router loses connection to the internet and shows as having no DHCP lease. The internet goes down for about 4 to 5 min at a time. This happens randomly and can happen multiple times a day then not happen for weeks. Its an intermittent problem. The wan interface shows 0.0.0.0 and says no connectivity.

After talking to Shaw they indicated the modem was working and had a good signal. They said there was nothing wrong. The first thing they told me to do was reboot the modem. I had tried that but went through the procedure again with them on the phone. They said the logs they had access to indicated the modem had been running fine for months. I have called back complaining many times with them now telling me to disable bridge mode and use the modem as my primary internet to try and troubleshoot the issue. I have replaced the ethernet cables with new ones bought recently as a further troubleshooting method.

I have tried running Ping plotter which did catch the device when internet stopped working. It showed my ping to google as being about 1500ms and the connection stops somewhere in a google data center and never gets to google.com. At this time the router shows 0.0.0.0 and no IP and no DNS. I assume I lose the lease and it takes modem 5 minutes or so to give me a new one? I have tried doing hard reset on modem and all connected network devices and updating the firmware on devices. I never lose local access to router its only the WAN that goes down. The light for ethernet port on modem and router are lit up just fine so they are talking to each other but no joy! I can ping the router but have no access to modem while it is in bridge mode. The suggestion to just stop using my third party hardware and my problems will go away is sort of really making me mad.

I don't believe the hardware I have is faulty. I could be wrong. I do not have another router to check if issues persists. I originally bought the unifi hardware because the wifi with shaw was crappy and did not even go halfway down my driveway. Now it goes down the road. Also I could not set the router to use google or cloudflare DNS and it was locked to ISP DNS. I'm pretty sure if I disable bridge mode and just use the ISP equipment all of my problems will go away. But I will lose the ability to control DNS unless i configure it device by device. Also I can't set up VLANS or do a bunch of other things I want to do. Any suggestions to intermittent issues with DHCP lease being lost and taking 5 min to get one back for my router would be appreciated.

 

Upon further inspection I lose my DHCP lease every 1 hour and 10 min. It takes about 5 minutes for the lease to be given to my router. While that is happening the internet is of course down hard.

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This might seem like the lamest suggestion ever but have you tried adding your providers DNS as a secondary DNS provider ? 
I've had similar issues with providers before that was solved with something as simple as that (however lame it seems). 

I hated using an ARRIS router when I was with Virgin Media (UK) and also did bridge mode too with my PFSense box infront of it. 

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Yes I added DNS and that did not affect the problem. I lose DHCP completely when it goes down. TY for suggestion though.

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I've got a similar system to yours - Shaw Gig and some Unifi stuff with a UDM pro and some POE switches. I had some dropouts as recently has Sunday just like you. I rebooted the switches and the UDM Pro and the problem seemed to get better.

 

You can also try to turn off auto-updating on the Unifi devices if you have it set up that way, because when updates randomly occur it can have blackouts on devices. You'll have to manually check for updates for Unifi items on the UKG2.

 

Lastly make sure that the Unifi USG-3P is able to access cool air and is not trapped behind or under items. That thing can get pretty warm and it may be shutting down and going into thermal protection.

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@ne0rmatrix

 

Are you sure 'bridge mode' is set up properly? Is the Arris TG3482ER3's LAN DHCP server turned off? Activating 'bridge mode' should do the latter by default, but some devices might fail to do this.

 

Is the USG receiving a WAN or LAN IP from the Arris?

 

Not sure if you did it based on how you worded your post, but did you try connecting your PC directly to the modem to test the uptime of the connection?

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On 5/18/2022 at 6:01 AM, ne0rmatrix said:

The wan interface shows 0.0.0.0 and says no connectivity.

Pretty sure something wrong with Arris. If Shaw insists nothing wrong, try asking them to replace it on speculation. If they refuse, then try this to force their hand:

 - unplug Arris from the wall, or just unplug the WAN,

 - call Support, say you lost your Internet, pretend you know nothing about Tech and how networking works.

 - confirm to them that Arris indeed has power (lie),

 - they will say they see no connection, while you'll say that power is OK and connections are ok, and when you reboot it nothing changes,

If you're successful they'll have to replace their box and hopefully whatever was giving you problems goes away with the old box.

 

Option2: switch to Telus, their 1G fiber is actually 1Gbit down and up

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  • 3 weeks later...

I found a solution that worked! I started by factory resetting all the Unifi equipment I own. I forgot both the switch mini's, the two AP's, and factory reset the cloud key gen2. After doing that and logging in I chose to set it up as a new device. I then turned the bluecurve modem back into normal mode. Next I switched it back to bridge mode. I then went through setting up IPv6 on the USG. It just worked! So I think turning the bridge mode off and then back on was the fix.

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