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Reserved DHCP addresses on Hub One

IngeJones
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Registered: ‎07-01-2014

Reserved DHCP addresses on Hub One

With devices I currently own and can be seen in the current DHCP table, I can see their IP addresses and get the router to fix or reserve the address, or chance it, or set it to be not reserved.   Unfortunately some addresses I try to allocate get the error message that it's already in use.  Although no device is shown to be using it.  I suspect these are addresses I reserved ages ago for devices I no longer own.  Is there any way to see a list of reserved addresses and clear out the old ones?

11 REPLIES 11
Baldrick1
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Re: Reserved DHCP addresses on Hub One

@IngeJones 

Doing a factory reset on the Hub should fix it. You can then start again with a clean sheet.

IngeJones
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Re: Reserved DHCP addresses on Hub One

Well that is fairly obvious.  I hope it was also obvious that I didn't want to try that as my first method of choice if there is any alternative.  Anyone else with a better idea?

VileReynard
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Re: Reserved DHCP addresses on Hub One

Dynamic addresses are reserved for a period - typically defaults to 12/24 hours.

But simply rebooting the router should flush its DNS cache.

"In The Beginning Was The Word, And The Word Was Aardvark."

IngeJones
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Re: Reserved DHCP addresses on Hub One

I did try that..  but there are still some slots I can't reserve for a new device.   Maybe I need to power off for a little while.  Though come to think of it.  we'd not want to lose reservations we had deliberately chosen to be static just because the router rebooted.   I know I did that for a few devices in the past that I no longer own and completely forgot to release their router-assigned static addresses.

VileReynard
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Re: Reserved DHCP addresses on Hub One

A long reboot would make no difference.

Many routers allow you to restrict the allowable IP address range for DHCP.

What IP addresses can't you reserve for the new device?

Don't forget that mobiles etc will allocate thenselves new addresses...

 

"In The Beginning Was The Word, And The Word Was Aardvark."

IngeJones
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Re: Reserved DHCP addresses on Hub One

I have restricted the range.  Of course the HubOne won't allow you to reserve an address outside that.  I had rather hoped to have 1-99 for Device-fixed IPs (eg PCs and we have also got fixed IPs for our mobiles on that network)  and 100-150 for devices the router will allocate a reserved IP and the rest of the range for random DHCP.   The ones I can't use I have discovered are ones which had been allocated to the Nest Protects which only pop onto the wifi for a couple of seconds every day.   But they could have easily got a new IP next time - there was no need for the router to be so mean about it lol.  Ok don't worry I am giving up on this I think the router just won't allow this sort of management.

wisty
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Re: Reserved DHCP addresses on Hub One

@IngeJones 

Not sure about the Hub1 - I don't have one to test, but using a BT Hub 5 ( albeit the business version), I found that if I set the DHCP to cover the range I wanted for device reserved IP addresses, I could allocate the reserved addresses as you would expect. If I then reduced the DHCP scope to exclude that range, the router remembered the reserved addresses(provided the device had been active) outside its scope and  issued those addresses when the device reappeared.

It's a bit of a faf, but it did work. Give it a try on your Hub 1, and let others know if it works.

IngeJones
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Re: Reserved DHCP addresses on Hub One

I think I have probably already discovered that as I have an IP camera which was allocated a reserved IP within the old range which is no longer in the new range.  It now shows up the same as devices with internally fixed IPs.   So to release its IP I'd presumably have to lower the range again before the "No" option became enabled again.   My actual problem was releasing ones I had reserved previously where I no longer have the item.  Unless I can get them to connect again from wherever they are living now, I will never get that IP back again other than with a factory reset

wisty
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Re: Reserved DHCP addresses on Hub One

As an outside chance. I have a couple of laptops/tablets that allow me to change the MAC address of the (wired) network card. 

If you happen to have such a device (the setting is in Device driver/Advanced/Network Address) and you know the MAC address of the devices, you could try spoofing the MAC address, connect the device and se if that will allow you to release them.

VileReynard
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Re: Reserved DHCP addresses on Hub One

Might be worth reducing the DHCP lease time while you are experimenting - at least you would only have to wait for a shorter time for an allocation to disapear.

My router says the minimum time is 1 minute!!! 😲

"In The Beginning Was The Word, And The Word Was Aardvark."

IngeJones
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Re: Reserved DHCP addresses on Hub One

@VileReynard my router has the minimum of 1hour, but yeah I did select that when I was messing about (fruitlessly)  I wouldn't want it all the time though as my nest devices are hopping on and off and sending me a crowd of notifications each time!!!

 

@wisty interesting idea!  I'll see if I have anything I can do that with