Devices connect to WiFi but is assigned no IP address

[FlyingCodeMonke]

Hi all,

I've had this issue for a long time and really hoping someone can help as it's driving me and my family crazy.

I have a Smart Hub 7 Pro and because it's an ancient house with thick stone walls, we need  3 WiFi extenders for full coverage. They all have ethernet backhaul to the Smart Hub (upstairs where the line comes into the house), although the extenders are daisy-chained because of the ridiculous way the house was wired (room to room, rather than each room direct to the attic!).

At various different times, the devices in the house keep dropping offline for no apparent reason. I eventually figured out that they're managing to connect to the WiFi network with a strong signal but aren't receiving an IP address via DHCP. After about 5 minutes (or turning WiFi off and on again on the device) it'll connect and obtain an IP address properly.

I've tried increasing and decreasing the DHCP lease time, which hasn't helped. I've tried assigning fix IP addresses via DHCP, which didn't help. I've even tried disabling the DHCP server on the Smart Hub Pro and configured my desktop computer (always online and connected via ethernet) to act as a DHCP server, but I've still got the same issue.

That said, now that I'm running my own DHCP server, I can see the full log output, and it's showing up something odd. Because the device knows about the server, it skips the DISCOVER message and goes straight to sending a REQUEST message to extend/renew the lease. Fine. The server replies with the ACK message - acknowledging the request and supplying all the configuration data, but it's like the device never receives the ACK message. It just keeps firing REQUEST messages. Then, it starts sending out DHCP DISCOVER messages, to which the server replies with the appropriate OFFER message...only to receive another DISCOVER message from the device.

Eventually, something I see DISCOVER, OFFER, REQUEST, ACK in the logs and then there's silence in the file because the device gets its IP address and can access the internet.

Once the device has connected, there is no packet loss on the network, so I don't think it's that. And other devices can be connected and working properly at the same time.

Also it's not always the same device that has trouble - sometimes it's my laptop, sometimes it's my wife's laptop or one of the kids' iPads, or the printer, or something else, or several not working at the same time...or sometimes miraculously everything is working fine. It's absolutely driving me bonkers that I can't figure it out.

WiFi devices upstairs have no problem getting online. It only seems to be the ones downstairs.

Can anyone help me at all please?

Thanks.

[JimM11]

@FlyingCodeMonke If you have the wireless extenders all connected via Ethernet backhaul, then there is no wireless to wireless connection between the devices as the Ethernet cable is taking care off that, what cable are you using between the devices ie Cat5e etc, they should all be connecting direct at 2.5Gb/s the NIC interface, you may have to look at the web manager interface to see that all 3 are connected to the hub, advanced wireless and the extenders should show you the state off play, https://192.168.1.254 to get there and inspect.

Have a look at the wireless securities at wpa3-T and see if the irksome devices work better on a compatible network connection that you may need to set up and test, dont think you can lower the main to wpa2-psk mode anymore. 

[FlyingCodeMonke]

Hi @JimM11  Thanks for your reply.

The cable between the devices is Cat6 and unfortunately they're not connected directly to the hub - I have to daisy-chain them, but they do all say "Connection Status: Good" and "Connection Type: Ethernet". Ethernet Status says 1000 Mbps rather than 2.5 Gb but that's because I've had to use an old gigabit switch to handle all the other ethernet devices I have. Unfortunately the WiFi extenders only have two ethernet ports 🙄

You're right, it's not possible to drop the security of the main network, but I tried turning on the compatible network like you suggested. I removed the details of them main network from the devices, but that didn't work either.

Can you think of anything else to try?

[bobpullen]

@FlyingCodeMonke - on one of the laptops could you try explicitly configuring the IP details via the network connection's TCP/IP properties? i.e. configure the LAN IP, gateway and DNS server on the device itself.

Not going to fix anything, but if the problem persists when things are configured like that then it would tell you that the issue can be related to DHCP (as the laptop wouldn't be dependent on it).

Where do your switches sit in the network topology? The fact that it only happens downstairs would suggest that the issue is isolated to when a device tries connecting to one of the extenders.

[JimM11]

@FlyingCodeMonke do have a look at your Ethernet setting and connections through switches etc, the extenders are showing wireless daisy chain effect unless the software does not report correct, see this picture although of a complete wifi disc connected through to a smarthub 2 were i am at currently working as the owner has a BT system that i had to get working for him....

[FlyingCodeMonke]

Hi @bobpullen and @JimM11 

Thanks for your replies. I wanted to give it a decent amount of time to be sure, but configuring one of the laptops with a fixed IP address and taking DHCP out of the equation does resolve the issue for that device. As soon as the laptop wakes up, it connects to WiFi and immediately has access to the internet.

As you say, not a long term solution, but at least it thoroughly points the finger at DHCP as I had expected.

The extenders are definitely connected via Ethernet:

The network layout looks like this. Apologies for the crudeness of the diagram!

[JimM11]

@FlyingCodeMonke Middle section is that using more than two connections as you have the additional Ethernet there so surely there is a switch also?

[FlyingCodeMonke]

Hi @JimM11 ,

Sorry, I wasn't at home when I drew that diagram and I did it from memory - I should've known better! I've just checked and the middle floor WiFi extender only has one ethernet device connected. The 1Gpbs switch in the kitchen is wired back to the 1Gpbs switch in the attic (it's only the playroom that's got the crazy room-to-room wiring).

I do have one more WiFi Extender that's not currently being used anywhere. I can try incorporating it anywhere in the setup if you think that would help. Last time I tried though, it complained of either being too close or too far away, I could never find a sweet spot for it.

[JimM11]

@FlyingCodeMonke Wiring all looks good Ethernet connection wise, do not remember anyone complaining about the DHCP operation on the Pro hub, but you have taken that out off the picture by disabling it and using the PC as the DHCP Server, switch to switch should be fine as passthrough on a non managed switch, would not bother about the additional extender unless you need it, but you will need to ignore messages about too far / too close as that has been reported before when mixed wired / wireless connection's, but do think they work just message is not 100% accurate. Mesh is not easy and devices can get confused when attaching especially when waking up from sleep mode in wireless operation.

[bobpullen]

@FlyingCodeMonke - thanks for the diagram, speaks a thousand words! 🙂

Clearly more complex than your average setup but I  agree with @JimM11 - it should work.

The one thing that perhaps raises an eyebrow for me is the far right extender here: -

Looking at your topology diagram, I'd expect that Playroom extender to report as being backhauled via the Middle Floor, not the Kitchen 🤔

I wonder if you wire things how the Hub Manager thinks you have them if there'll be any change in behaviour i.e. instead of the Playroom extender terminating on the Kitchen switch, is it practical to try wiring it to the Kitchen extender instead? Looks like you'd need to remove the Ethernet device that's currently connected to the Kitchen extender to make room.