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DDNS DHCP server ptr still remains

Posts: 14
1423     0

Hello all, 

I have configured DDNS on my DHCP server to update automatically via DDNS the DNS server.

When a device is connected after the DORA process, the A and PTR record are automatically registered. 

But when the device is not anymore connected, after lease time, the A record is removed but not the PTR record.

I don't understand why the PTR record remains because when the device moved to another location, it gets a new IP address and we have two PTR record (the old and the new one)


Is there anybody that can explain me why and have a solution to this situation ? 

Kind Regards,

Re: DDNS DHCP server ptr still remains

[ Edited ]
New Member
Posts: 5
1423     0

Having two PTR records (the old and the new one) is a common scenario in DDNS. The reason for this behavior is here. Lets say the client is in network1 originally. The DHCP server performed DDNS and added A & PTR records corresponding to network1 in DNS. Now, when this client moves from network1 to network2, it does not send a request to delete the previously updated A & PTR records corresponding to network1. When the client gets a lease from network2, it is the DHCP server which performs the DDNS for the client i.e. A &  PTR records corresponding to network2. At this time, the A record is replaced since DDNS update is happening to the same Forward mapping zone. But the PTR record is not replaced as the reverse zones corresponding to netwk1 and network2 are different. So, the old PTR record remains in network1 reverse zone and the new PTR record is updated to network2 reverse zone. However, once the lease expires,  the DHCP server should delete both A & PTR records for that client from the respective zones.
Enabling "One lease per client" can be a solution. This is detailed in Admin Guide section "Configuring DHCP Lease Management". However, please note this setting can be changed only at Grid & Member levels and not specifically for Networks or Ranges. Also, please consider that all clients will be affected with this setting change.

Re: DDNS DHCP server ptr still remains

Posts: 14
1423     0

Hello Viz, 

Thanks for the answer, 

It is how I see the process also when a client moves from one network to another one in DHCP. 

In my case, the device is registered with a host record because the device is configured with static IP. When we enable the DHCP on the device, it receive an IP address and is automatically registered in the DNS thanks to DDNS process (A+TXT+PTR record created).

The old static IP where we had a host record becomes only a PTR record and is never deleted from the DNS. This is the issue that I have for the moment.

Have you got also the same comportment ? 

Have a nice day,

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