LM1200 repeatedly dropping link

So just thought I would pass this along. I ended up returning the LM1200 due to the connection issues. I bought another vendors equipent but also expierenced some similar, albiet not as extreme connection issues, but ocasionally I would go through cycles where I was disconnected and reconnected. I noticed that I was getting a IPv4 Address and a IPv6 address. After trying some different things, I finally set the protocol type to IPv4 ONLY. Ever since I have done this, the connection has been 100% stable, I change it back to IPv4+IPv6 and i have sporadic connection issues again. There seems to be something weird happeneing with Verizon when getting a IPv4 and IPv6 address.

Since I have already returned my LM1200, I don't recall if disabling IPv6 was an option.

I just got my LM1200 earlier this week and would like to join the growing list of people having this same problem.  I want to connect the LM1200 in bridge mode to my pfSense firewall (core2duo with Intel quad gigabit card).  I have Verizon service with the card the local store recommended when I showed them my LM1200.

First day: I hooked everything up accessed the LM1200 via web interface at 192.168.5.1 using a PC through my pfSense, got a connection after a couple failed attempts and used it for about 4 hours until I was done, and manually disconnected.  Ever after: when I connect the LM1200, it quickly says it is connected, then cycles the link (link light down then up after several seconds), then says disconnected and cycles the link again.  Every now and then, it will be up long enough to get maybe 3 or 4 pings to 8.8.8.8, but that is rare.

I can hook directly to a single computer just fine.  When I connected to a single computer and let it work for a few minutes, then swung the ethernet cable over to the pfSense, I got good pings for about 20 or 30 seconds, then the cell connection dropped again.

I have already disabled IPv6 on all of my PCs, pfSense and LM1200 - I avoid using IPv6 anyway - just call me old-school.  I will certainly try router mode tonight in hopes of getting my whole network online.

Let me know if I can provide anything to contribute to a solution - I really want this to work in bridge mode in hopes that at I could get at least some access into my network from outside.  (I used to host several web sites and frequently remote into my home network from outside util I moved - I'm sure web-hosting is out of the picture over consumer-level cell, but bridge mode is what makes the most sense to use for a router/firewall anyway)

Also, thank you to everyone who has been contributing.  This being my first venture into cell data (since comcast backed out after telling me they could hook me up), I was starting to think I missed some fine print in some verizon usage clause or just didn't understand how the LM1200 was supposed to work.

John 

Hi John, any update on the cycling disconnects with Verizon and bridge mode? I'm a NETGEAR partner and turning anywhere I can to see if there is a fix on the horizon. I really want to buy these in bulk, but my eval unit is exibiting the same behavior as described in this thread: erratic cycling disconnects in bridge mode, with Verizon coming back with a new IP address each time, where router mode seems to be stable. Thank you.

JohnPeng & Et al.

What a troubling issue indeed. Please read below for what I've discovered, if you've been reading this topic for months you'll find it quite interesting.

AT&T hotspot SIM works fine using Bridge Mode in my LM1200, no link dropping no lost IP addresses, this we know already.

All of my testing was done using a MikroTik hAP ac2 running 7.1.3 software for reference.

The Verizon hotspot SIM on our business account in the LM1200 in Bridge Mode receives an IP then drops the ethernet link approximately 26 seconds later and of course loses the IP address, then approximately 23 seconds later the ethernet link is recovered and the cycle repeats. This is the first time I've seen the behavior documented to this level of detail.

I decided to leave the hAP ac2 running all night long, utilizing the LM1200 with the Verizon SIM and left no devices connected to the router. Curiously the Verizon LTE connection never dropped while no other devices were connected to the router. Further, the ZeroTier VPN connection stayed stable and I was able to remotely access the hAP ac2 without issue. This behavior was most curious and so began my attempt at a theory of why. I had something to do with devices connected behind the NAT of the hAP ac2. Sure enough when I connected a device to the router the next morning the LM1200's  connection began the drop and reconnect behavior described above.

What is different when the router connects via the Verizon IP vs though the NAT of the router? Should be nothing, right? A proper NAT translates the device IPs behind it and Verizon shouldn't know any better. How could Verizon know? After digging back into years of IP header theory back in my college days, I had mine (it took a few days) - and it was the TTL value was wrong.

I added a rule in the hAP ac2 that adds 1 to the TTL of all IP packets passing though the NAT. After doing that, the Bridge Mode connection became solid. No cycling of the ethernet link, nor IP addresses releasing and renewing. Of course, upon removing the rule adding 1 to the TTL the connection is dysfunctional as described above. After dozens of tests, the behavior is controllable and predicable based upon the TTL change.

Ok, so your thinking then the Netgear programmers just need to fix this by adding 1 to the TTL when the LM1200 is in Bridge Mode. Wrong!

Just for giggles (does anyone really giggle in these moments?) I decided to really go for it and see what the heck was going on and see if I could determine who's issue it was, now that I'd confirmed what it was. No need to blame Netgear if indeed they were not at fault. It's easy and that's wrong.

Since the hAP ac2 has a USB port and supports the Verizon USB730L functioning as a pass though bridge device I decided to do an experiment with the same Verizon SIM used in the testing with the LM1200. Surprisingly both the USB730L and the LM1200 exhibit the same behavior where the connection is unstable with an unmanipulated TTL and adding 1 to the TTL stabilizes the connection.

Verizon's network used to work properly without TTL manipulation with the USB730L and the hAP ac2. At some point it stopped working. I thought it was a bug in the hAP ac2s software and said well hopefully they'll fix it someday. It wasn't the hAP ac2s software, something has changed Verizon's network, I'm not sure when it changed it's been a while. This is Verizon's issue, not Netgear's.

Unfortunately, I don't know how to get this to the right folks at Verizon. Most people who hear this are going to think it's network gibberish when attempting a support call. I tried to get help from Netgear regarding the device and was promised a call back the next day, the call never came and my Case #: 45696214 was closed in 7 days because I was unresponsive. This is where Netgear is at fault. I'm utterly disappointed in Netgear support, closing the case with no call back is absolutely unacceptable.

Hopefully this helps someone.

--Mike

JohnPeng Can you clarify that you work for / represent Netgear? What is taking so long to sort this out? Is there a solution on the horizon or should we just return our products?

JinTu 

In regards to what the hAP ac2 is setting the TTL to, I don't know what I was thinking in my previous reply.

Before adding 1 to the TTL the TTL is 63, after of course it is 64.

Setting the TTL to 64 on egress to the LM1200 also mitigates the issue when using Verizon LTE.

I had to reply to this only because you can throw me in mix for having repeated dropped connections every 30 seconds. I can only get a consistent connection whenever I plug the LM1200 straight into my laptop, or at night ill carry it over to my smart tv and plug it in there so i watch Netflix.

How is this going on for over 6 months and still not resolved? I blame Netgear just as much as Verizon on this.

I can not setup any of my unifi devices or anything. I am literally just tied to the freaking modem with a flipping ethernet cord with nothing connected to it.

For some reason, whenever I try and have multiple devices everything just fails. I can see the flipping cell tower from my window, i got great signal.

Every time i loseconnection it picks up a new IP address. I just don't get it. Its even worse seeing how long this thread goes on for. No urgency.

I just purchased the LM1200 as a backup WAN link for my TL-R600VPN router. I have Verizon and have experience the same issues as everyone else -- the link is only up for about 5 seconds, then the link drops and this cycle repeats itself. I should have went to this support page instead of wasting several hours of my time trying to figure this out! Very frustrating. My LM1200 works fine if I connect it to a PC ethernet jack, but it exhibits this behavior if I connect it to one of the WAN ports on my router. I have tried both Bridge and Router mode, with the same results. Has anybody found a solution to this? Does anyone know if I ditch this LM1200 for another verizon hotspot like the Verizon 5G M1000 (it has an ethernet jack) will I just have the same problems?

Thanks!