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I use a building Wi-Fi network that I don't control. Normally it works fine, but fairly routinely I have trouble where my laptop (Windows 8.1, Intel Dual Band wifi chipset) gets "limited network access" -- specifically, it seems to have trouble with DHCP and acquiring a valid IP. This problem often lasts hours or even a day, and then resolves as mysteriously as it begins.
Often, another device, like my Android phone, will be able to connect just fine. If so, I have been able to make my laptop work fine by selecting a static IP based on the subnet and gateway my phone gets from DHCP. I don't think this is how you're supposed to use networks.
ipconfig \flushdns, ipconfig \renew, and ipconfig \release don't help. And I cannot ping 8.8.8.8 at all when in the failed state. I also cannot seem to ping the DHCP server, which is the same as the gateway.
Is there anything I can do to make this problem stop happening? Or anything that would be good to check the difference between my phone and my laptop? For that matter, is there anything I can ask the (somewhat distant and not very technically skilled) operator of the network to do, other than "reboot the router"?
ikrase
Posted 2019-11-05T08:00:34.540
Reputation: 121
2Are you able to ping the DHCP server after configuring a static address? Are the PC and the phone connected to the same access point? (You can use "Wi-Fi analyzer" apps to see the APs' MAC addresses (BSSIDs), they will usually be different for each physical AP.) In general, even determining what the problem is will likely need the operator's help. – user1686 – 2019-11-05T08:06:09.580
1@grawity I'm not sure how to know the DHCP server's address to ping it -- is it the same as the gateway? – ikrase – 2019-11-05T08:12:00.237
@grawity It looks like both the computer and the phone are on the same AP -- this wifi network has several APs. One notable thing: My phone's MAC can be changed but I don't think I can change my PCs' MAC. – ikrase – 2019-11-05T08:16:29.160
@grawity Looks like I cannot pic the DHCP server, which is the same as the gateway, with either device. – ikrase – 2019-11-05T08:35:40.623
3I've been in the same situation myself. Tell the building's IT department. The router is most likely either running out of IP addresses due to too narrow a scope or excessively long lease times, or its DHCP server keeps crashing and the router is being rebooted as a workaround. Either way, the IT guys need to know that users are being affected so they can start investigating. The best thing you can do is tell them ASAP and specifically mention that you're unable to acquire an IP address with one specific device. – Mr Ethernet – 2019-11-05T09:28:20.563
@MrEthernet Does the fact that the subnet mask is 255.255.255.0 suggest that there's only 250-ish unique IP addresses available?
This building doesn't have a real IP department, but I will see what I can do. – ikrase – 2019-11-05T09:38:47.133
2Yes but you might have much fewer. There are two issues here: how many valid IP addresses are in that subnet (253 max) but more importantly, how many IP addresses are available via DHCP. The limiting factor is the DHCP scope, which by default is usually something like 192.168.1.2 - 192.168.1.99. If the guy doesn't know what he's doing, the router might only allow 98 wireless clients to connect and isn't freeing up their IPs until 7 days after they've disconnected. This is an educated guess based on typical default settings but you could be looking at as few as 98 devices/week. – Mr Ethernet – 2019-11-05T09:41:49.247
1I would give the inexperienced IT guy easy instructions so that he can fix it himself or at least look in the right place. "Please try decreasing the lease time from 7 days to 1 day and increase the End IP value from 99 to 200". If he can't figure that out and/or you want a quick and dirty workaround, give yourself a static IP above 100, which is likely to be outside the default DHCP scope so unlikely to give you a conflict. E.g. 192.168.1.251. This is all based on the assumption you're running out of IPs. Only the IT guy himself can see if this is the problem though. – Mr Ethernet – 2019-11-05T09:49:55.920
1Also, see if you can find out the make and model of the router by browsing to the default gateway's IP address in your web browser. E.g. 192.168.1.1. See if the logon screen tells you what it is. You can then easily find out all the default settings and see what's probably going on. That will help you to guide the IT guy. – Mr Ethernet – 2019-11-05T09:58:21.267
1Have you tried disconnecting from the network on the laptop and reconnecting? While that doesn't solve the underlying issue at play, it would at least be a workaround until the IT dept can resolve the issue. – JW0914 – 2019-11-05T12:09:26.877
@JW0914 that very much doesn't work. – ikrase – 2019-11-05T20:19:17.347
1@ikrase That rules out an issue common in Windows with certain routers and the issue is what others have suggested, the DHCP server itself. – JW0914 – 2019-11-06T11:10:14.560