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Wifi ok but no DHCP - LAN is fine

  • zigzak
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24 Apr 2021 10:46 #1 by zigzak
Wifi ok but no DHCP - LAN is fine was created by zigzak
Hi,
I've recently put in a Draytek 2865ac router connected directly with a VDSL connection. It's running firmware 4.2.3_BT, which according to it's own check is the latest.

I have a strange problem with Wifi though. Devices will find the Wifi, accept the key, and connect ok.. .BUT they aren't receiving an IP address - on a device where I can check (such as my iPhone) it just shows the "auto" 169.x.x.x style address.

However other devices will work just fine, and a device that isn't working will suddenly start working some time later. This is happening with various phones, an Alexa, and also with a laptop. Cabled devices are totally fine. The router is running the DHCP service - the pool is 160 IP addresses and they don't generally have more than 40 devices in the DHCP table so I don't think it's running out of addresses.

In terms of troubleshooting on my own phone I tried switching wifi off/on, forgetting the network and rejoining, I rebooted the router, I switched off 5Ghz range, 2.5 and 5 are both set for auto channel so I did try selecting a couple of other channels based on the results from AP Discovery - nothing made any difference. I was onsite for a couple of hours yesterday and my phone didn't connect at all, yet others were connected and working the entire time.

I have the same SSID and key with WPA/PSK2 configured for 2.4 and 5Ghz. I haven't enabled any kind of schedule, MAC filtering, or anything like that.

I do have VLAN enabled with P1 to P4 and SSID1 l inked to LAN1 which is the one having the problem.

Any ideas where I go with this? The client is understandably pressing for a solution.

David

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  • hornbyp
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24 Apr 2021 13:57 #2 by hornbyp
Replied by hornbyp on topic Re: Wifi ok but no DHCP - LAN is fine

zigzak wrote:
Any ideas where I go with this? The client is understandably pressing for a solution.



Anything useful in Syslog?

Otherwise:

Could they be exceeded the maximum number of Wi-fi clients? I can't find that number documented for the 2865, but there are 'hints' that it might be 64. Presumably, that would be per Radio/Band.

Does this issue occur on both 2.4GHz & 5GHz? (might need some additional test SSIDs, to force a specific connection)

What happens if you add a failing wireless client to the Bind-to-IP list?

Unlikely, but worth a look - it the 'Strict Bind' option set? (I've seen this 'set itself' - on my 2860n following firmware upgrades. I don't think anybody believes me :) )

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24 Apr 2021 14:29 #3 by piste basher
Replied by piste basher on topic Re: Wifi ok but no DHCP - LAN is fine
May or may not be related but for a while I was running a 2927ac with 4 AP903s ( :oops: ) in a mesh configuration. The APs were located - 1 in an upstairs bedroom, 1 downstairs in the lounge, 1 downstairs in the kitchen and 1 outside in the garage. Initially I was using 802.1x "fast roaming" but later changed to "straight" WPA2/PSK.

With this setup I not infrequently found that my iPhone had no internet connection although it had an apparently strong wifi signal. On investigation I found the symptom you describe - the phone had a "black hole" IP address. Turning wifi off and back on on the phone would resolve the situation, but clearly that was not ideal.

I have now switched to using 2 AP960C APs downstairs and the single AP903 in the garage. I have never experienced this IP address issue since switching to this setup. I can only think that somehow the presence of too many :?: roaming options had perhaps confused the phone, or maybe the operation of the wifi in the 960 is in some way "improved" over that in the 903 (and the 2865?) ??

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  • zigzak
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24 Apr 2021 15:40 #4 by zigzak
Replied by zigzak on topic Re: Wifi ok but no DHCP - LAN is fine
Thanks for the replies.

@Phornbyp - I think I'll try establishing a separate SSID on LAN3 or something with a different subnet and see what happens to the problem, thanks. Never thought to enable/look at SysLog will do that. I did tried turning off 5ghz as they never had this problem with the previous ISP supplied router and I'm pretty sure it wouldn't have been dual band.

@Piste - Thanks, I don't have any linked access points (there are other access points but they have different SSIDs and are different makes, etc,) so maybe not exactly the same problem. Switching wifi off/on on my own phone didn't seem to solve the problem, nor did restarting the router.. which is worrying, lol.

David

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