Unable to delete DHCP reservations and corresponding DNS entry


How to get rid of this DNS entry? Where are the DHCP reservations and the DNS entries stored?

EDIT: The file where the entries have to be deleted is /var/lib/dnsmasq/dnsmasq.leases

But you have to stop dnsmasq before updating that file, and then restart it after the modification.

I did that, but I still think that is a bug, that the entries cannot be deleted from the UI (in constrast to other entries). This should be fixed.

I think the issue with trying to develop a way to do this via the UI is that dnsmasq doesn’t provide any way to do this natively. So it’s not as simple as just issuing a command.

  • Other entries CAN be deleted. Why not the discussed entries?
  • Even if there is no direct command, removing the line from /var/lib/dnsmasq/dnsmasq.leases and restart dnsmaq is just a couple of lines of code.

Because is a not expired lease given to a dhcp client. As soon as the client does not renew the dhcp-lease due time it is removed from /var/lib/dnsmasq/dnsmasq.leases

Can you explain the use case for removing not expired leases manually?

As described above, changing a DHCP configuration to a fixed IP configuration leaves the old DHCP reservation INCLUDING the wrong DNS entry in the DNS server and makes the PC/server unreachable.

Reconfigurations of an address schema. You want to apply a certein schema and want to reassign IP-adresses. Currently is it not possible to delete and reassign adresses which the DHCP server issued on a random basis.

Malfunctions/Bugs. Administering DNS/DHCP servers for 20 years, it happens that orphaned or inkonsistent entries have to be tidied up.

Hello Carsten

It works for me, and I’ve been managing DNS/DHCP for 35 years!

Keep a very small DHCP Pool. I use 241-254 for ALL clients. That’s more than enough.

DHCP does NOT make entries in DNS. I do NOT have use for this function, which is a source of bad planning / lazyness!

All Servers, NAS, Printers have a static IP in my Networks - but also a reservation for the same IP as DHCP (manually). I do this because often I’ve seen printers “lose their memory - or config” after updating, and they switch back to DHCP. This way, I get it right, even if I have to setup a server or printer anew - the IP is correct.

If you MUST use DHCP -> DNS, switch it off before changing anything, but YMMV… I do prefer good or even better planning!

For me, this is a non issue!


My 2 cents Andy

AFAIK this is covered by making a IP reservation :


I can confirm that when converting a DHCP entry to static in the DHCP settings will “free” the old IP and remove the entry - as soon as the dhcp host uses the new IP…

I can’t say anything for DNS entries, as I do use DNS, but no automatic…

Did you make a DHCP reservation? That might remove the old entry, but I was talking about the case, that a device got a dynamic address from DHCP because the default setting was DHCP and I then gave this PC a static, non-DHCP address (which is even not in the DHCP range). In this case the DHCP/DNS reservation is NOT deleted and cannot be deleted manually.

I also tried to conver the dynamic IP assignment with “Make reserveration” into a pseudo-static one, but this also failed with the error message “there is already a host with this name”. This is actually true, because the specific host in this case was the Active Directory domain controller, which got a temporary DHCP address because a virtual hardware upgrade deleted the old network card and created a new one. After assigning the static address in Windows, the Active Directory was still not available because of the wrong DNS entry which could not be deleted.

The “IP reservation” button failed with an error message “Host already existing”. See answer above to @Andy_Wismer .

This is NOT true in Nethserver. NS created DNS entries for evey DHCP reservation, as described above. The DNS entries are in /var/lib/dnsmasq/dnsmasq.

I do the same thing as you and the PC with the problem accidentally got a DHCP adresse because of virtual hardware change. This could not be fixed any, because Nethserver kept the undeletable DHCP reservation with the wrong DNS entry in dnsmasq even though the PC (actually server) was reconfigured to a fixed adress already.

I will admit using the older NethGIU instead of Cockpit to manage DHCP/DNS. There is no automatic DHCP -> DNS entry using the old NethGUI (980). At least not so far in my 25 clients servers or at home.

And as such, an entry can be removed in the old GUI…

I do not know about a DNS entry from DHCP, as said, this did not happen on my NethServers… (so far!).

Try switching the Server/PC back to DHCP… (For testing that you can remove that entry…).

Virtual Hardware can be allocated almost ANY MAC Address, so you should be able to replicate this!

I doubt that this is a old/new UI problem and clain that the IS such an entry also in your servers. The DNS entry is hidden in the file /var/lib/dnsmasq/dnsmasq and is NOT displayed in the Nethserver UI, but dnsmasq resolves it. To test, do the following:

  • Have a client get a dynamic IP address.
  • start nslookup, set server address to nethserver it is not the default, query the client name. It should give the assigned address. Also check /var/lib/dnsmasq/dnsmasq for an corresponding enytry.
  • Go to the client and change from DHCP to static IP configuration and give it another ip-address.
  • Retest step two. Result: The old entry is still in /var/lib/dnsmasq/dnsmasq and dnsmasq still resolves the name to the wrong, old address. And the wrong reservation cannot be deleted (at least in cockpit).

BTW: No, the mac address should not be replicated everytime you change an interface, and it is not needed for static ip addressing. But even then, if is a bug that the wrong entry cannot be removed from Nethserver in case you forget to forge the MAC address, because the wrong DHCP-address cannot be fixed any more. Therefor it must be possible to delete dynamic leases (maybe with a warning confirmation).

I will have to check… Since I moved DHCP to OPNsense, NethServer dose not handle DHCP anymore, it still handles DNS (together with NethServer).

The randomness which with NethServer handles the PTR record if there are 2 A Names in DNS (as a CNAME is only possible for NethServer, not for any other hosts…) was my primary reason for this change.

But I still have 1-2 friends who use NethServer as Firewall, DHCP & DNS.

I need to see if I can do a test either Wednesday or Thursday. Today and tomorrow I’m outstation, at clients…

So it is quite a useless discussion. I described a bug in Nethservers DHCP/DNS handling and you just said, that you do not use it, as you don’t to DHCP with NS. It is no surprise that a NS-DHCP-UI-bug does not appear if you don’t use NS-DHCP.

I said i do not use it any more, I did use it a lot until 2019/2020. (Most clients upgraded their old firewall in those two years…).

This sounds like a use case; did not take assigning an IP outside the DHCP range into account.

The problem ist not adressing outside the DHCP-IP-range, but the static assignment of the IP-address in the PC. There is no deregistration. A similar problem appears if a temporary test VM gets an address and is deleted afterwards or a temporary device gets an IP or you want to change the DHCP adressing change. All are use cases, where you have to delete existing leases, to the it must be possible to to this.

How to delete Ip Dhcp Pool In Cisco Switch

Cisco ios dhcp reservation and cisco dhcp lease release, sharing buttons:.

00:00 this video show you how to configure

00:01 Cisco IOS DHCP reservation this machine

00:05 as you see get an IP address one or two

00:09 assisted 52:21 from the DHCP server in

00:13 our example DHCP server is my Cisco

00:16 router as you see show IP dhcp binding

00:21 will show you which addresses assigned

00:25 to the clients for example here this is

00:28 the only IP address that the cisco

00:30 router assigned to the client now I

00:33 always want this MAC address or this

00:36 machine get an IP address 192 160 160

00:41 8.50 dot 30 for example confetti IP dhcp

00:49 pool create a pool the name of this pool

00:53 type any name for example here Tariq and

00:56 type the host IP address one at 168 5230

01:01 and type the client identifier

01:05 what is the client identifier the client

01:08 entity far as you see here this is the

01:11 client identifier this is the MAC

01:13 address of this machine from 0 0 to 1 d

01:17 as you see here and windows 7 machine or

01:21 in this address and 0 1 represent the

01:26 media Ethernet type okay so type the

01:32 client identifier cabbage from him and

01:35 best it here and click enter before I

01:40 see before I disable and enable the

01:42 network interface on this PC exit I

01:46 should leave the previous IP dhcp

01:51 binding clear IP dhcp binding and type

01:56 the IP address of the previous binding

01:58 which is here or you can type asterisk

02:01 means you will clear all addresses click

02:05 enter and now open this device again

02:10 disable the network until

02:13 scarred and it led here in a beam that

02:16 will get the new IP address one at to

02:21 one sixty eight dot fifty dot thirty

02:24 let's see click on details thank you for

02:28 watching

Related queries:

Other suggestions:.

DHCP Client options and Remove DHCP

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How to Detect Who Deleted a DHCP Reservation

DHCP-Server event: DHCP Reservation deleted

In order to create an alert triggered each time whenever someone deletes a DHCP Reservation:

Whenever someone deletes a DHCP Reservation, you will receive a similar alert:

Netwrix Auditor Alert: DHCP Reservation Deleted

Monitor Deletions of DHCP Reservations to Avoid System Unavailability

The deletion of a DHCP reservation can cause IT services to be unavailable. For instance, users can experience problems accessing e-mail, file servers, SharePoint, etc. And because users won’t be able to access files on corporate shared resources or use their mailboxes, the IT helpdesk will see a significant increase in ticket volume. To minimize the risk of system unavailability and the resulting failed access attempts, IT administrators need to keep an eye on DHCP reservations and spot any deletions as soon as possible.

Netwrix Auditor for Windows Server provides visibility into Windows Server activity and delivers actionable information about all Windows Server access events and changes, including the deletion of DHCP reservations. Then, by using the Interactive Search feature, IT staff can generate an easy-to-read report showing all the details about a deleted DHCP reservation, including who deleted it, when and where the deletion occurred, and other details. The solution also notifies IT administrators about deleted reserved IP addresses by sending them email alerts in order to further help prevent system unavailability.

Delete Dhcp Server Reservation - Netkrom AIR-BR500GHP User Manual

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DHCP reservation

When connectiing via WI-FI to our company Network am supposed to get a reserved IP via our DHCP server....

I dont get the rerserved address but I do get an address.......

when checking ADDRESS leases using the DHCP admin tool on my windwos server I see the address listed with my iPad name but the Lease expiration says INACTIVE and the type = NONE

the other iPad's (they dont have reservations) are listed and have TYPE=DHCP which seem to be correct

any idea why my iPad does not seme not be able to use a reserved IP..I have double checked my MAC address over and over for typo's but its in there accruratly

If I delete the reservation.....and then just do a regular DHCP like the other iPads do once again I DO get an addres handed to me ...but when veiwing the DHCP admin tool I never see my ipads name in the name field where as all the other ipads do have their iPads name listed one their assigned IP line

this I have observed for quite some time and I have no explaination for why myiPad's name does nto get displyed withing the ADDRESS LEASE details screen

I called Apple support on the phone and as soon as I started talking about DHCP..the tech said they dont offer that kind of support ! I even bought applecare in order to have this kind of supporrt as we go forward using this device in our windows enviroment.... To be honest, I am strugging to get these iPads to be a usefull tool for my users ina Windows business environment .......I see where its a great device for one to have for your personal use....but boy its hard alternative to a windows tablet...... and to hear there may be very limited support for issues like this that are rooted on TCPIP connectiviey and such is dissapointing to say the least

[email protected]

iPad 2, iOS 5.1

Posted on Apr 2, 2012 7:11 AM

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Apr 2, 2012 8:27 AM in response to decoursey

Set up the DHCP reservation on the DHCP server. Connect to the wi-fi network and go to the settings for that network and select "static ip". Set the static ip address to the same as the reservation address on the DHCP server, make sure the subnet mask, router ip, etc. are all set correctly here as well. You should be good to go.

dhcp delete reservation

Dhcp Reservations

About › Forums › Windows Update › Dhcp Reservations

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In order to fix the whole issue of DHCP Reservation woes, Microsoft has also announced that it will be fixing the entire problem of Windows XP compatible routers. Actually, these are router problems which all the customers who want to use a new Netgear router should opt for. However, these may not be able to access Internet by default. Instead, they have to connect the router by using some special software. The idea behind this is to provide better coverage and speed of the Internet to the users. Unfortunately, there were many internet users who were not able to use the Netgear router due to the fact that the manufacturers did not provide the compatibility list for Windows XP based routers.

But, Microsoft has now announced that they are going to fix the issue by providing all the information about this situation. Actually, it has been found that a certain virus may be present in some of the drivers of these routers. Therefore, it was concluded that all the customers should use the drivers from the anti-virus software to be able to remove this virus. This virus had been causing a lot of damage to the routers. And, in order to fix the problem, Microsoft released a soft-ware which was capable of resolving all the network compatibility issues. When a customer is running this soft-ware, all the other drivers of the router should be compatible with the Windows XP operating system. Thus, the DHCP Reservation problem would be resolved.

The statement from Microsoft also stated that once the customers are running the CPAP systems, they should turn off the hardware function of the router so that the reservation and switching off of the operation of the software should be avoided. The only thing that the users need to do is to follow the instructions that were provided by Microsoft. Actually, many people had reported about the compatibility issue between the Windows XP and Windows routers. They should try to remove the virus from the routers in order to avoid problems in the future.

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