LM1200 repeatedly dropping link

[kpbong]

This is the same behavior I'm seeing. I'll add that if I log into my UDM Pro and add a static route on the command line:

ip route add 192.168.1.5 dev eth9

Then I can use the web interface and see that the device is connected, etc. When I swap the WAN interfaces and try to actually use the modem, it resets itself as you describe.

[mal7887]

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.

[kpbong]

I was intrigued by this report so I tried eding the APN to change the PDP from IPV4IPV6 to IPV4 only. This did not change the behavior I'm seeing in bridge mode, where the device resets itself when my router attempts to get a DHCP address. Router mode seems more stable with IPv4-only PDP.

[bbatty66]

Can you give a bit more by way of specifics please? Per the thread, I'm assuming this is using an LM1200 on Verizon. If running in router mode, what did you use for gateway and DNS addresses?

[kpbong]

I posted further up in the thread. I’m using an LM1200 on Verizon with a BYOD data SIM. In router mode I’m using the default 192.168.5.1 address and DHCP range.

[JohnPeng]

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@mal7887 wrote:

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.

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This is an important information. Thanks for your feedback.

As our investigation shows, even though the device settings can cause the issue, eventually, the issue happens on the Verizon network side since the network intitiates the disconnection and the issue happens intermittently. 

Thanks

[Fiddlin]

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.

[AaronWTCI]

This thread has been going since August of 2021. We still have no solution and its obviously not some one off thing. I have opened a ticket with Verizon support as well just to get another angle on it. A tier 2 tech told me he would monitor my connection and escalate the info to engineering. I am still waiting to hear back from them. I have sent 2 follow up emails but no response yet.

[AaronWTCI]

I also shared the link to this with them as well. Maybe Netgear and Verizon could get it figured out together..

[JohnPeng]

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@AaronWTCI wrote:

I also shared the link to this with them as well. Maybe Netgear and Verizon could get it figured out together..

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Thank you for following up with Verizon on your side as well. We also escalate the issue to Verizon, but the response is slow. 

John

[JohnPeng]

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@Fiddlin wrote:

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.

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Thanks for the detailed information. Based on the discussion here, we know that pfsense can trigger the disconnection issue easily, but the disconnection initiated on the Network side. Really need to get the network logs to find out why. We could reproduce the same issue with other Netgear fixed wireless products on Verizon network. Even with LM1200, we can see that the issue happens intermittently, but when it happens, the link will keep resetting for a while before it finally gets stable.

Thanks

[cgh]

Using verizon here. I am experiencing the same issues in this thread. The disconnects between LM1200 LAN port and router port are a layer 2 issue correct? Link up/down/up/down. Why does the (MAC) layer 2 connection between the LM1200 change? What does that have to do with the Verizon wireless connection? I am using a edge router 4. For comparison, if I disconnect the coax from my cable modem, my modem and router are still connected layer 2.

[JohnPeng]

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@cgh wrote:
Using verizon here. I am experiencing the same issues in this thread. The disconnects between LM1200 LAN port and router port are a layer 2 issue correct? Link up/down/up/down. Why does the (MAC) layer 2 connection between the LM1200 change? What does that have to do with the Verizon wireless connection? I am using a edge router 4. For comparison, if I disconnect the coax from my cable modem, my modem and router are still connected layer 2.

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Seems you are using Verizon cable box connecting to LM1200 WAN port and a router connecting to LM1200 Lan port. If this is true, the issue discussed in the thread doesn't apply to your setup. The Verizon disconnection issue happens when using Verizon wireless network.

Thanks

[cgh]

John, Apologies. I am not using a Verizon cable box, I am using a LM1200. I was attempting to draw comparison to another type of modem and the behavior when the service provider connection gets dropped. This might help eliminated confusion if the LM1200 LAN to router L2 connection remained persistent through provider connection dropouts. No other modem that I am aware of drops L2 link when the service provider connection drops.

[JohnPeng]

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@cgh wrote:
John, Apologies. I am not using a Verizon cable box, I am using a LM1200. I was attempting to draw comparison to another type of modem and the behavior when the service provider connection gets dropped. This might help eliminated confusion if the LM1200 LAN to router L2 connection remained persistent through provider connection dropouts. No other modem that I am aware of drops L2 link when the service provider connection drops.

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OK. I got your point. By default, LM1200 is set as Bridge mode. It will pass the network assigned IP to your router. That is why when the wireless network disconnects the connection, the device will try to reconnect, refresh the IP and pass it to the router client.

Please try setting the device to Router mode to see whether it will help. 

Thanks

[petro1020]

Same issue here. Verizon data-only SIM, LM1200 connected to Ubiquiti USG Pro 4 as a failover WAN connection.  Bridge mode simply doesn't work with a router at all (I've also tried two regular consumer model routers and get same result). 20 years of network engineering/IT experience and have tried all the different configurations listed in the topic to no avail (IPv4 only, 1 minute keep-alive, etc.). I am going to try the double-NATed approach with Router mode, but this is awful considering this device is advertised on the box as being "Certified with Verizon Wireless". Even if it is a "Verizon issue", Netgear should be responsibile for working with them to fix it if they've certified this device as working with their network.  Guess I'll go the route of returning this device if we don't get a resolution soon 😞 .  Also, it's a bit disconcerting that I just bought this device and it doesn't seem to be listed on the list of available Model Numbers to choose when posting on this forum...

[mrgenius]

@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]

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@mrgenius wrote:

@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.

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Right now, the issue in Verizon's hand. We have provided the device information for them to check the network logs. Seems this is not a device issue since we noticed the same issue also happens on other devices. Will push Verizon to provide the update asap.

Thanks for your patience.

[JinTu]

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@JohnPeng wrote:

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Right now, the issue in Verizon's hand. We have provided the device information for them to check the network logs. Seems this is not a device issue since we noticed the same issue also happens on other devices. Will push Verizon to provide the update asap.

Thanks for your patience.

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@JohnPeng for anyone experiencing this issue who wants to reach out to Verizon to put additional pressure on them to investigate/resolve the issue, is there as specific case or ticket number that we can reference to direct their attention to the case Netgear already has open about this?

[AaronWTCI]

Verizon has never responded to my ticket after the first day. The tech I spoke to promised to get back to me the next day. I have since sent three emails asking for updates and have not heard a word back. Awesome support from these mega companies! I would suggest everyone just start calling in and reporting trouble, daily. Somebodies stuff is obviously not working right. I plan to call in again as soon as I have the precious time too.

[mrgenius]

@JohnPeng

Here's an idea: Many other competing LTE routers have an option to power-cycle the unit when failing over between the LTE modem and wired WAN. If that feature was put into the LM1200, it would make the unit usable in the context of this string and the problems with Verizon. Yes, it would take a bit longer for the device to come back online, but it would come back with a stable LTE connection, and effective failover would be achieved. My customers wouldn't think anything different in behavior.

[labellama]

@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

[solah]

@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]

@labellama this is an interesting discovery. I just did a quick check and by default my pfSense-based router is setting the TTL (and hop limit for IPv6) to 64 for the gateway health checks (but this varies for other traffic on failover) What is the minimum TTL/hop limit that you are seeing on egress from the hAP ac2 after making this change?

[labellama]

@JinTu I’m seeing a TTL of 54 to 8.8.8.8, 113 to 8.8.4.4 and 50 to 1.1.1.1, these are the TTL values after the manipulation rule that adds 1 for all egress to the LM1200.

From my testing, forcing the TTL to 64 or 65 on egress did not change the dysfunctional behavior.