Devices connect to wifi but no internet - IP addresses not allocated.

[hvorrath]

We have a new NBN connection, with a Sagemcom Fast 5536 modem supplied by Optus. We normally have a PC, a wifi repeater and another device connected to the modem via ethernet. We also have a lot of devices connected by wifi, a couple of phones, an iPad and another tablet, an Apple TV, and so on. All was fine until a friend came to stay with 2 phones, a tablet and a computer. Now we are getting problems where all the devices connect to the wifi, but they don't get an IP address allocated, so there is no internet connection. Once the device gets an IP address, it's fine, but if you have it off for a while and then turn it on again, it may fail to get an address, and so no internet.

As far as I can tell, you should have over 250 IP addresses available. Is there some limitation in the Sagemcom modem? Is there some setting I can change to stop this happening? 

We didn't have this problem with our old Optus cable modem - have had meetings in the house and had a roomful of devices connected to the internet without a problem. 

[YetAnotherAcc]

Sounds like you might be running into a max simultaneous connection per WiFi frequency issue.

I don't know what the hard limit is on the 5366 is (had a quick look on the device and could find no info) but the latest 3864v3 has a default hard limit of 32 devices for 5Ghz + 32 devices for 2.4Ghz.

How many devices do you have each frequency at any given time?

[hvorrath]

Not more than 10 per frequency, usually less than 5.

We have a wifi repeater plugged in to an ethernet connection which is quite close to the modem. We are wondering whether there is some conflict between the modem and the repeater.

We have a second repeater some distance away (the length of a garden) and from that we use ethernet over power to reach rooms further into the house (we have a very long thin property).

We've had this wifi repeater setup for ages and it was all fine until we got the NBN instead of cable and a new modem.

[YetAnotherAcc]

So much for that theory. Even if they stuffed up with the 5366 and it has a max of 16 (which is what the early 3864's apparently had) I would think that'd you'd be ok.

Is it just the 5366 that refuses to give an IP address or is it all the repeaters as well?

Have you checked the error logs on the 5366?

Have you checked if there is an overlap in the repeaters DHCP range and that of the 5366?

[hvorrath]

I think it is both the repeaters and the modem, but it's hard to tell what's connected via what. The devices that connect via ethernet over power to a repeater show up on the My gateway page as being ethernet connected, even though it is actually ethernet->repeater->repeater->ethernet. And like all the best bugs, its intermittent - sometimes it works and sometimes it doesn't.

I didn't know I had error logs, so thanks for that tip. I went looking and found them. The 27 pages of errors seem all to be "DNS name resolution failure." which doesn't tell me anything much. Would that be what you'd get if you weren't connected to the net?

Haven't checked if there is an overlap in the repeaters DHCP range and that of the 5366. I think that might be something to investigate if I can find the manual for the repeaters, but where I am it's bedtime, so I'm going to continue this exercise in the morning.

Thanks for your help. I'm an IT person, but my understanding of networks is pretty basic, so getting some pointers about where to look and what to look for is very useful.

[YetAnotherAcc]

I think it is both the repeaters and the modem, but it's hard to tell what's connected via what.

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If its both then an IP conflict seems like a possibility, if its just the 5366 then I was thinking it might be just its wifi.

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The devices that connect via ethernet over power to a repeater show up on the My gateway page as being ethernet connected, even though it is actually ethernet->repeater->repeater->ethernet.

That makes sense as the repeater issued the devices IP via a wired connection, so that is its connection type.  How it then gets to My gateway is irrelevant. 

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And like all the best bugs, its intermittent - sometimes it works and sometimes it doesn't.

Yeah, and so much fun.

Are you saying that the devices connected to the repeater via ethernet over power also have IP problems, and its not just wifi devices?

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I didn't know I had error logs, so thanks for that tip. I went looking and found them. The 27 pages of errors seem all to be "DNS name resolution failure." which doesn't tell me anything much. Would that be what you'd get if you weren't connected to the net?

The log is fairly crap unfortunately: the time stamps do not work, you can't clear the logs, and some of the messages are vague/misleading. You should work through those logs though. There shouldn't be that many different types of errors in the log and there should be a clue in there.

Would that be what you'd get if you weren't connected to the net?

 Yes, but you also get those intermittently like during a reboot, so that info is of no use without proper time stamps. 

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Haven't checked if there is an overlap in the repeaters DHCP range and that of the 5366. I think that might be something to investigate

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I'm guessing that there will be an overlap. Even if that's no the cause of your current problem they shouldn't overlap so its best to fix it.

if I can find the manual for the repeaters

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You should check if the repeaters have error logs as well.

[hvorrath]

Still having the problem. Sometimes devices connect, and sometimes they don't, with a message saying they can't get an IP address - eg "IP configuration failure" on my Android phone, sitting about 2m from the repeater.

To avoid any conflict between the modem and the repeaters, we turned off wifi on the modem. So everything is connecting (or not) via the Ubiquiti Unifi repeaters. 

If we reboot the modem, it seems to solve the problem, but only temporarily.

I have the controller running for the repeaters, so I can see what they are doing. My phone (which won't connect at the moment) shows up as a client of the repeater, but with the following message:

Problem:

DHCP Timeout

Solution:

Please check that your DHCP server is accessible and properly configured

I assume that the DHCP server lives somewhere inside the Sagemcom Fast 5536 modem. I've looked in the settings and everything looks reasonable - it says the IPv4 pool starts at 192.168.0.2 and finishes at 192.168.0.254 and the lease time is 1 day. The server is obviously accessible at least some of the time.  But it does look as though if you drop a connection on a particular device, it doesn't give you back an IP address when you get back in range, or turn the device on again.

I turned the modem off and on again, and my phone now connects. I'm a big fan of turning it off and on again, but it could get very tedious if I have to do that every time someone walks out of range with their phone or turns off their tablet.

[YetAnotherAcc]

Yeah, its looking like a DHCP clash.

The 5366 has a DHCP server and the repeaters will have DHCP server as well. You should only have one DHCP server running.

I believe the Unifi repeaters have a DHCP relay mode, just enable that on all repeaters. That will force all IP assignment requests end up at the 5366,, which will then assign them without conflict.

[hvorrath]

I'm going through the Unifi Controller options looking for some way to set the relay mode option as you recommend, but I haven't yet found one.

What I did find, under Guest Controls, was the following:

Post-Authorization Restrictions

192.168.0.0/16

172.16.0.0/12

10.0.0.0/8

and there is an option to ADD IPV4 HOSTNAME OR SUBNET

Questions:

- should the top line of the restrictions be 192.168.0.0/254? Is the /16 restricting the number of IP addresses available?

- should I try to add an IPV4 Hostname or Subnet?

[hvorrath]

In the other thread about issues with the Sagemcom 5366, there is a suggestion about turning off DHCP on the 5366. 

Would that be more sensible than trying to turn it off on the Unifi devices?