Actually to be clear, I don't need to reboot the server, I can just toggle the DHCP off and on again, which re-initialises the DHCP service.

Still not great though.

Note also that I tried disconnecting and reconnecting the cable to the device before restarting DHCP. That didn't work. I did the same after restarting DHCP just to initiate the network connection on the device. That then immediately picked up the address - the same one that it failed with previously 

Hi @ckdash,

Can you capture and post the following info?

• Your DHCP settings
• Client reservations (if any)
• Client lease list when you have the issue
• Client lease list after it's working again
• DHCP logs during the problem timeframe

D-C wrote

Hi @ckdash,

 

Can you capture and post the following info?

• Your DHCP settings
• Client reservations (if any)
• Client lease list when you have the issue
• Client lease list after it's working again
• DHCP logs during the problem timeframe

  @D-C 

as requested:

DHCP settings really basic.

I set the Gateway/Subnet to 192.168.0.1/24

I click button to "Update DHCP Range"

I edit that DHCP range to

192.168.0.100 - 192.168.0.254

Lease time 120 minutes

Legal DHCP servers not checked

DHCP L2 Relay not checked

No client reservations. 
I do have some fixed IP addresses, but I keep them in the lower hundred addresses that are outside the DHCP range. 
 

Ways the best place to get the client lease list - there are several places e.g. Insights->known clients, the clients page, possibly even Past connections 

It is currently behaving itself so can't get logs right now. I have set up remote logging so I'll keep an eye on it. 

@ckdash, I don't use the TP-Link router, but I assumed it was a feature; a post about a year ago said it wasn't.  Nothing in your setup looked suspicious, but is it possible that you have another DHCP service running on your network?

  @D-C No other DHCP server. Even if there was, I wouldn't expect the client to keep requesting an address if there was another DCHP Server that had given it an address.  Plus I'm not sure how rebooting the TP-Link router's DHCP server would fix things if that was the case.

@ckdash, rogue DHCP service or static address in the DHCP range are the usual suspects, so didn't want to rule them out.  Is the IP address rejection always the .136 address or is it random address in the DHCP range?  That might indicate a static IP issue.  If you increase the lease times, it should decrease the frequence of the issue, but you can also reduce it when you want to troubleshoot.

  @D-C - thanks for the thoughts. 

It's not always the same device or IP. 

A DHCP server reset always fixes it. 
When it recurs, it's for a different device and IP. 
I've set up an external logging site with alerts so I'll find out when it next happens rather than randomly checking my router logs to see if there are any devices failing.