Router DHCP failing on me?

[.Griff.]

I have a Netgear Nighthawk D7000 that I've used for a year or two with no issue.

As I have multiple devices on my LAN at any one time I use the internal DHCP server to assign devices on the LAN IP address automatically in the 192.168.0.2 - .254 range.

Nothing earth-shattering there.

However, of late, I've noticed that more than one device has lost internet connection and when I've triaged the issue the device has been assigned a 169 address. This has happened to my main PC as well as a Samsung Q9FN.

Any obvious reasons why this would happen lately? I've had two (ish) years of no issues and then this is happening more and more often of late. No firmware upgrades on the D700 either.

DHCP server failing on me?

 

[.Griff.]

Wired directly via ethernet.

 

[.Griff.]

How often does this occur?

What's your current network topology? How do both devices exhibiting issues connect? Is it via the same switch or completely different runs?

Once a week may be that I'm aware of. I've been away on a course last week so haven't been here to have much visibility but it did it again yesterday afternoon.

Symptoms differ for each device (due to the nature of the device itself) but on the Windows PC websites will fail to load suddenly and IPconfig shows a 169 address assigned to the PC. On the Q9FN Youtube videos will stop and constantly attempt to buffer. Going into Network settings will show a 169 address assigned to it.

PC is connected directly to the D7000 via ethernet, the Q9FN does go via a Netgear switch (used for AV devices).

Rebooting the router fixes the issue each time.

Have you checked the cable? No cuts, no kinks, securely plugged in both ends? Check especially where the cable goes through a doorway.

Admittedly I haven't. I probably should as we have two cats and I wouldn't put it past them chewing on stuff they shouldn't. I'll do that tonight.

 

[.Griff.]

If you want to dig in at a technical level, install Wireshark on your PC and start a trace to watch the DORA process (Discover, Offer, Request, Acknowledge) that makes up DHCP.

Start the trace and then run ipconfig /renew from a command line to see what happens. To filter the Wireshark display, type "bootp" into the filter box (DHCP is a feature of BOOTP)

Good suggestion. The course I alluded to was on OSINT and we covered DORA as part of that. I'll give it a go.

 

[.Griff.]

Give your devices static IP addresses, make your DHCP scope smaller, and set devices to have their own Static (just your PC and TV for now).

Cheers. I'd considered doing just that but reluctantly held off until now as there's circa 15 devices on the LAN (most wireless) and I'd only seen the symptoms exhibited on the two devices I use daily - PC and TV.

I might just do what you suggest and assign static IP to the two devices I use most often.

 

[.Griff.]

Dunno if it helps but my D7000 started doing the exact same thing after 2 years of ownership. It mainly affected wireless. I tried everything I could, firmware, beta firmware, moving router, new cables etc. in the end I had to replace the router and as soon as I got a new one, no issues.

That's interesting then. Same router and same time period.

Now you mention it I've had periodic issues with my iPad (over wireless obviously) and I just ended up resetting the networking settings on it. Maybe it's the same issue as experienced with the PC and TV.

 

[.Griff.]

You got any static address on the lan in the same range as the dhcp pool? Sounds like an ip conflict to be honest. WIndows doesnt always pop up a wee moan about it either, first you know is when devices stop working and fire up a gash 169 address.
Maybe move your dhcp range to another subnet if you want to nail it down.

No statics in use.

Have you recently added or reset any devices on the network that might have a DHCP server on them?

The 169.254.x.x/16 address range is an old IBM standard called APIPA and it’s what your devices get handed out when there is no DHCP server running.

Just because they are connecting over the WLAN doesn’t mean they are getting an IP address from the router. If, for some reason, the Netgear thinks it’s not the DHCP server for the network, it won’t give out any IP addresses and it (or something else on the network) will instead hand out APIPA addresses. Can you check if the DHCP server on the Netgear is running? Port 67 is the one to check. If it’s not, that’s why it’s handing out APIPA addresses. If it is, then something else is handing out APIPA addresses. That could be a wireless extender, a NAS unit or even the Virgin Hub if it’s suddenly come alive.

Nothing has been added and/or reset lately. Certainly, nothing that has a DHCP server on them.

The DHCP server is definitely running on the D7000. I'm working from home and I can see it assigning IP's to the work laptop and mobile correctly.

As for something else handing out IP addresses, there is nothing on the network that might do that. No NAS, not sure where the reference to the Virgin hub came from as I''m not, and never have been, with Virgin. Yes there are a couple of wifi extenders but this IP issue is affecting wired devices.

 

[.Griff.]

Any Powerline adapters. It's quite possible for them to connect to a neighbour's network and give you access to their DHCP server as well as your own.

No powerline adapters.

The two (that I've noticed) devices affected are wired directly to the D7000 (well the Q9FN does go via a switch but certainly no powerline adapters or wife extenders being used for these devices)

 

[.Griff.]

The more I read the more I see references to inherent issues with DHCP on the D7000. Not to mention a user on here with the same issue on the same router.

What is your DHCP lease time set to? Long or short? You could just make it VERY long.

You cannot amend the lease period on the D7000 unfortunately. No idea what the predefined lease is but I've seen references to as little as 15 minutes.

You say that you can see the Netgear allocating IP addresses but clearly the Windows PC isn’t getting an IP address, so it’s not.

The Windows PC is getting an IP address. At least initially but more on that below.

What appears to happen is this -

Wake up > Switch the device in question on > DHCP on D7000 correctly assigns IP > work away as normal for a few hours > lose internet connection > check assigned IP and it's changed from 192.168.0.x to 169.254.x.x

If the reference I've seen to the D7000 having a lease period of 15 minutes is correct I assume the following is happening;

Device gets IP assigned correctly when turned on > once 50% of the lease period has passed the device requests to extend it but gets no reply from DHCP server > tries again after 75% expired but gets no answer > tries again after 87.5% expired but gets no answer > lease expires and device in question broadcasts for another IP from any DHCP server and gets 169.254.x.x assigned instead.

 

[.Griff.]

You only set the lease to such a short time when you're changing DHCP servers. Set it to a week or a month.

I think you've misread my comments.

Namely, I stated there is no ability to set/change/alter/amend the lease period on the D7000.

 

[.Griff.]

Ah, I'd missed that. Sorry. Anyway, I thought the default lease time on the D7000 was 1 hour.

You might be right mate. Either way, it seems like multiple devices are requesting lease extensions and are not being acknowledged leading to them broadcasting for another DHCP server and the ensuing issue.

 

[.Griff.]

I have a D7000 v2 and after a year I just went back to ISP supplied stuff. It kept dropping connections exactly like yours and after the first month of ownership Netgear weren't interested in helping. I did get a replacement but that was as bad as the first one I brought.

That makes three of us in this thread with same router and same issue. It can’t be a coincidence. Maybe I’ll look for a replacement.