Duplicate DNS Entries -- Forward/Reverse Zones

[jeffkelly]

I read other posts about this issue but want to introduce our specific details in hopes someone can assist with a resolution. No matter what we do, the problem remains.

Thanks in advance to all who respond.

---------------------------------------------------

Need help with DNS.

Issue: Forward and reverse lookup zones have duplicate entries. Despite having a low TTL and scavenging enabled, records do not delete when computers disconnect from the network.

I have three ways to obtain and IP address from the DHCP server (1) Ethernet (2) Wireless (3) VPN. As the DHCP server assigns IP addresses, an A record is created in the DNS Forward lookup zone and Pointer record in the reverse lookup zone. Because neither is deleting when a workstation disconnects, my DNS server has many duplicate entries in both zones (Forward zone duplicates IP address while reverse duplicates NetBIOS name and host IP number).

Our DHCP server properties are configured as:
[ul square]
[li]General TAB the, “Lease duration for DHCP clients” is set to 8 hours.[/li]
[li]DNS TAB, the following radio buttons are checked:[/li]
[ul disc]
[li]“Enable DNS dynamic updates according to the settings below:[/li]
[li]“Dynamically update DNS A and PTR records only if requested by the DHCP clients.”[/li]
[li]“Discard A and PTR records when lease is deleted.”[/li]
[li]“Dynamically update DNS A and PTR records for DHCP clients that do not request updates (for example, clients running Windows NT 4.0)”[/li]
[li]On The Advanced DNS TAB, the Assign IP addresses dynamically to clients of: both is checked [/li]
[li]“Lease duration for BOOTP clients: limited to 30 days” [/li]
[/ul]
[/ul]



Our DNS Server properties are configured as:
[ul square]
[li]At the DNS Server level: [/li]
[ul disc]
[li]Server Aging/Scavenging Properties – “Scavenge stale resource records” is not checked.[/li]
[/ul]

[li]At the Domain level: (Forward Lookup Zones) & (Reverse Lookup Zone) [/li]
[ul disc]
[li]Zone Aging/Scavenging Properties – “Scavenge stale resource records” is checked.[/li]
[li]No-refresh interval and Refresh interval is configured at 7 hours. [/li]
[li]Refresh Interval is set to 7 hours[/li]
[li]Domain Host (A) Properties: “Delete this record when it becomes stale” is checked. [/li]
[li]Time to live (TTL): is configured to 20 minutes. [/li]
[li](Reverse Lookup Zone) [/li]
[ul circle]
[li]At the Pointer (PTR) : “Delete this record when it becomes stale” is checked [/li]
[li]Time to live (TTL): is configured to 15 minutes. [/li]
[/ul]
[/ul]
[/ul]



Regards,

Jeff

 

[Freestone]

At the DNS Server level, Properties, Advanced tab check Enable automatic scavenging of stale records and choose a Scavenging period.

 

[jeffkelly]

Freestone: I took your advice and the issue remains. It is causing serious routing problems on my network.

I welcome other ideas.

 

[58sniper]

Despite having a low TTL and scavenging enabled, records do not delete when computers disconnect from the network.

Why would DNS records delete when a machine disconnects? DNS is not aware when a computer disconnects. In a normal environment, a computer requests an address from DHCP. When the address is accepted, DHCP updates DNS accordingly, and that DNS record stays until scavenging takes place.

Pat Richard MVP
Plan for performance, and capacity takes care of itself. Plan for capacity, and suffer poor performance.

http://www.ucblogs.net/blogs/exchange/

 

[jeffkelly]

OK, a poor choice of words. Let me rephrase: the scavenging process (as presently configured) isn't removing inactive DNS records.

 

[Molenski]

I don't know if you still have the issue but if so, is there anything in here that might help?

http://blogs.technet.com/b/networki...afraid-of-dns-scavenging-just-be-patient.aspx