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R7000 keeps offering IP but device cannot connect

ringlord
Apprentice

R7000 keeps offering IP but device cannot connect

I keep on having connectivity issues on my R7000.

Even when I connect a wired device, I see my R7000 handing out what I think is a prevoiusly assigned IP to that device.

But the offer is never accepted or my R7000 does not register this offer as being accepted and keeps on offering it.

So the end result is no connectivity.

I cannot trace what is happening, the only thing that I see is these DHCP offers every 10 seconds.

This even happens when I connect directly to one of the LAN ports of the router.

 

[DHCP IP: (192.168.1.12)] to MAC address 8C:C1:21:5B:60:75, Monday, Feb 06,2017 20:36:04
[DHCP IP: (192.168.1.12)] to MAC address 8C:C1:21:5B:60:75, Monday, Feb 06,2017 20:35:54

 

@ElaineM offered me a procedure previously that I assume cleared out the DHCP lease database.

But it cannot be that I have to do that reset procedure every time I reconnect a previously connected device?

What can I do 

Model: R7000|Nighthawk AC1900 Dual Band WiFi Router
Message 1 of 13
LeeH
Prodigy

Re: R7000 keeps offering IP but device cannot connect

Turn on all your network connected devices.  Open a web browser to the routers web interface.  Go to the Advanced tab and select Setup the select LAN Setup under that.  Use the +Add button to reserve all your IP addresses one by one.  Click the Apply button at the top of the screen.

 

If you add any devices to your network add a reservation for each one of those as you add them.  Cell phones are especially bad at IP conflicts.

Message 2 of 13
ringlord
Apprentice

Re: R7000 keeps offering IP but device cannot connect

Of course that would defeat the purpose of DHCP where the router does all that admninistration for you.

 

In my case it is as if the router remembers what MAC address 'owned' that IP in the past and the tries to offer it to the device.

But either the offer does not reach the device

or the device does not accept it

or the router does not hear the ACK

 

The problem is that with this Netgear firmware I cannot trace the communication.

Message 3 of 13
StephenB
Guru

Re: R7000 keeps offering IP but device cannot connect


@ringlord wrote:

Of course that would defeat the purpose of DHCP where the router does all that admninistration for you.

 

 


Not really.  The router still assigns the addresses.

 

With DHCP, the client "leases" the address, and needs to renew it when the lease expires.  Sometimes if you reboot the router, the client thinks it still has the lease, but the router of course doesn't remember that.  That particular problem usually only happens if you have ethernet switches (so the client doesn't see a dropped connection).

 

Do you have any devices that use static addresses?

 

Message 4 of 13
ringlord
Apprentice

Re: R7000 keeps offering IP but device cannot connect

Hi Stephen, yes I have static IP addresses outside the DHCP range.

 

I already did this to work around these DHCP issues.

Message 5 of 13
StephenB
Guru

Re: R7000 keeps offering IP but device cannot connect


@ringlord wrote:

I have static IP addresses outside the DHCP range.

 


Since they are outside the range, there is no conflict there.

 

If you are using a mix of static and dhcp - did the address conflicts disappear when you assigned the static addresses?

Message 6 of 13
ringlord
Apprentice

Re: R7000 keeps offering IP but device cannot connect

No, this is what happens :

 

A device on the network with mac address 8C:C1:21:5B:60:75 gets IP 192.168.1.12 (inside DHCP range)

At a given time I unplug or reboot the device.

At that time we see that the router offers IP 192.168.1.12 to that same device (when it reconnects)

For an unknown reason that IP is not assigned to the device and the router keeps offering it.

Message 7 of 13
LeeH
Prodigy

Re: R7000 keeps offering IP but device cannot connect

That is why Netgear created the IP reservation capability under the Advanced tab, Setup then LAN Setup under that.  Making IP reservations that cause the same IP address to be assigned to the same MAC address is a good thing to do.  You will most likely continue to have issues until that is accomplished.

Message 8 of 13
StephenB
Guru

Re: R7000 keeps offering IP but device cannot connect


@ringlord wrote:

 

A device on the network with mac address 8C:C1:21:5B:60:75 gets IP 192.168.1.12 (inside DHCP range)

At a given time I unplug or reboot the device.

At that time we see that the router offers IP 192.168.1.12 to that same device (when it reconnects)

For an unknown reason that IP is not assigned to the device and the router keeps offering it.


I guess the bad behavior is the last step?  I'm not sure what you mean by either "that IP is not assigned to the device" or "the router keeps offering it.  Do you have a wireshark trace of some sort that shows this?

 

Normally I would expect the assigned device IP to remain the same in this scenario.

 

Message 9 of 13
ringlord
Apprentice

Re: R7000 keeps offering IP but device cannot connect

Yes the bad behaviour is the last step.

I only have a logfile in the web interface of the R7000 router that keeps repeating every 10 seconds.

[DHCP IP: (192.168.1.12)] to MAC address 8C:C1:21:5B:60:75, Monday, Feb 06,2017 20:36:04
[DHCP IP: (192.168.1.12)] to MAC address 8C:C1:21:5B:60:75, Monday, Feb 06,2017 20:35:54

I also have a client device that does not get an IP addres.

I did not use wireshark (I don't know If I would be able to interpret the logging from that tool)

 

 

Message 10 of 13
StephenB
Guru

Re: R7000 keeps offering IP but device cannot connect


@ringlord wrote:


I only have a logfile in the web interface of the R7000 router that keeps repeating every 10 seconds.



[DHCP IP: (192.168.1.12)] to MAC address 8C:C1:21:5B:60:75, Monday, Feb 06,2017 20:36:04
[DHCP IP: (192.168.1.12)] to MAC address 8C:C1:21:5B:60:75, Monday, Feb 06,2017 20:35:54

  

 The client might be re-requesting an address every 10 seconds.  So this could be a client problem.  What device is it?  Is it connecting over wifi or ethernet?


@ringlord wrote:

I also have a client device that does not get an IP addres.

 


How many clients do you have?  Also, if you turn off the one that is repeating, does the client get an address?

 

 

Message 11 of 13
ringlord
Apprentice

Re: R7000 keeps offering IP but device cannot connect

I think that is indeed the problem.

Combined with help on another forum I found that the device that is probably NOT getting an IP becasue it was connected to the LAN port of the R7000.

It appears that DHCP only works on the WAN port of the R7000  OR on the LAN ports, but not on both.

Thinking about that, it sounds logical, I guess.

Message 12 of 13
StephenB
Guru

Re: R7000 keeps offering IP but device cannot connect


@ringlord wrote:

I think that is indeed the problem.

Combined with help on another forum I found that the device that is probably NOT getting an IP becasue it was connected to the LAN port of the R7000.

 


DHCP should definitely work on the LAN port - and in fact the DHCP server won't work on the internet port.  

 

The R7000 has a DHCP client that gets an internet address from your ISP.  But it's DHCP server is only for your home network (LAN and WiFi).

 

Plus it is assigning an address.  The client is either not getting that assignment, or is it is misconfigured somehow.

Message 13 of 13
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