[Hub3] Modem mode stops working

[Kack_Hans]

Heya,

I've seen a few posts regarding problems in modem mode, but couldn't find anything that describes my issue.

My hub3 is downstairs, with a cat5e ethernet cable in port 1, going all the way up to my office and connecting to my TP-Link Archer AX53 - which works as the main supplier.

I simply don't want to use the hub, it's featureless, buggy and the load times on it's local webinterface are horrendeous and there is a ton of bufferbloat without SQM/QoS

Initial config/setup worked relatively smoothly with the guidance from previous threads on this board, but the actual usage has become a massive drag.

On to the point:

Every once in a while (It's safe to say somewhere between every 12 to 48 hours) the internet connection just dies and does not recover.

My TP-Link router reports the lack of a physical connection.

The cat5e ethernet cable is fine as the port LEDs are flashing green on both devices. It never caused any issues while I was at Talktalk and hasn't been causing any issues while I've put the the hub3 for a four days in router mode.

I don't know how to 100% rule out the TP-Link router, but it works completly fine if it's just used in access point mode, while the hub is in router mode (tested over the last 4 days).

As mentioned above, I've tested everything in router mode from Thursday and reverted it to modem on Monday, with the internet breaking down again last night. 192.168.100.1 is unreachable.

Now, I really would like to see the logs of the hub3 to potentially discover anything there, but I always need to factory reset it, set it back to modem mode and it just magically works again.

When I plug the ethernet cable out of my router and plug it into my PC, so that the PC is directly connected to the hub in modem mode, I do get internet. If I now try to connect to the web interface of the hub (192.168.100.1) I get redirected to http://192.168.0.1:5422/?tool_troubleshoot&mid=Troubleshoot, which is unreachable too.

Does this indicate that there is a fault in the hub3 that is causing that issue in modem mode?
Am I overlooking something in the settings of my third party router?

I have already raised this with tech support while they stated that modem mode is unsupported, they sent the following (see screenshot):

I've read in previous threads that you do have to configure modem mode again if your WAN IP changes. Is that what's happening? Is there any way to prevent this?

[legacy1]

It sound like VM balls up modem mode with a firmware and don't want to fix it and make people use router mode because O look its stable! Not the bloody point VM! Your a ISP that gives out WAN IP's your not a CGNAT ISP! support modem mode

If you have a PC with 2 NIC you can hook one up to modem mode the other to your router using MS internet connection sharing as you run wireshark with filter or you can get a smart switch with port mirroring between your router and hub to view the traffic

port 68 or port 67 or arp

https://www.wireshark.org/

to see whats happening when it drops but you may need to test with with reg setting on your NIC

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{NIC with WAN IP}

DhcpConnEnableBcastFlagToggle 0

DhcpConnForceBroadcastFlag 1

as TP-Link like to use Broadcast reply that may be the problem

or TP-Link had a firmware update and thats the problem.

[jpeg1]

The WAN IP changes very rarely, so that's unlikely to be the cause. 

Could your long LAN cable have been damaged, would it be easy to replace it? Cat 5e is OK but a cat 6a cable is usually more robust and has better screening. 

[Kack_Hans]

Hi all,

Thanks so far for all the replies

@legacy1 I don't have two NICs, but I may have a smart switch, I'll see if it supports port mirroring and then see if I can figure it out. I might also get

@jpeg The ethernet cable works fine, I'm 100% sure of it. I'm about to replace it with a cat6e this weekend anyway, but I doubt this will fix the issue, as I can connect directly to the hub and get internet back, as I've outlined in my original query.

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@Kack_Hans wrote:

The cat5e ethernet cable is fine as the port LEDs are flashing green on both devices. It never caused any issues while I was at Talktalk and hasn't been causing any issues while I've put the the hub3 for a four days in router mode.

When I plug the ethernet cable out of my router and plug it into my PC, so that the PC is directly connected to the hub in modem mode, I do get internet. If I now try to connect to the web interface of the hub (192.168.100.1) I get redirected to http://192.168.0.1:5422/?tool_troubleshoot&mid=Troubleshoot, which is unreachable too.

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[legacy1]

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@Kack_Hans wrote:

@legacy1 I don't have two NICs, but I may have a smart switch, I'll see if it supports port mirroring and then see if I can figure it out. I might also get

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What you need is three ports available two in a isolated untag VLAN for router and hub and the other to a NIC for mirroring traffic from the port to the hub. So you still need a NIC like this for wireshark

BENFEI Ethernet Adapter, USB 3.0 to RJ45 1000Mbps Gigabit LAN Adapter Compatible for MacBook, Surfac...

[Kack_Hans · Accepted solution]

Thanks for the helpful advice, @legacy1

I was able to narrow it down and enabled "Get IP using Unicast DHCP" on the TPLink router.

If anyone else has the issue:

1. Head to your tplink interface (tplinkwifi.net) and sign in
2. Head to advanced
3. Under network, head to Internet
4. Under Internet, expand Advanced Settings
5. Tick "Get IP using Unicast DHCP"

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[legacy1]

Yes VM are at it again which they should not do because not all routers have such a option.

unless there is a rfc about this saying broadcast replies to be phased out it should still be allowed