DHCP server using Dynamic DNS overwrites correct entry?

[Dave Willcocks]

Hopefully someone can help me with this one.

I have 2 DHCP servers in an office. Both are set to always update
DNS.

Scenario

A Windows XP client machine is has an IP address of 10.1.1.1, issued
from DHCP server #1
After a reboot it collects IP address 10.1.2.1 from DHCP server #2
When I try to ping the Client the name resolves to the old address.
I check the DNS and see that the record is still 10.1.1.1, so I delete
the record and ensure that all DNS servers have no record for that
machine.
WINS has the correct address.
On the client machine I run ipconfig /registerDNS.
The DNS record is updated succesfully and and I am able to ping the
machine from the rest of the network as it resolves correctly to
10.1.2.1
Approx 2 hours later I am no longer able to ping, the client is
resolving back to the old address (10.1.1.1)
Checking DNS I see that the record has returned to it's old address.

When I check the DHCP servers I see that both have leases for the
client machine. DHCP#1 has 10.1.1.1, DHCP#2 has 10.1.2.1

I am assuming that DHCP#1 is re-registering the address with DNS and
overwriting the correct entry.

I assumed that DHCP only updates DNS when it gives out a lease, but
this would appear to show that DHCP must keep updating DNS at certain
times.

So what I'm asking is this:
If I was to change the the DHCP server to update DNS only when the
client requests would this fix the problem?
What is the schedule for DHCP updating DNS (if this is what it does),
and can this be altered?
Does the older DHCP lease have priority as it is the original owner of
the record?

BTW to fix the problem in this instance I deleted the lease on DHCP#1

Cheers in advance to all you networking gurus out there.

dave

 

[licknlabia]

You don't have replication setup between the two.

One needs to be the SOA, the other one will be a replication partner.

- lnl


Hopefully someone can help me with this one.

I have 2 DHCP servers in an office. Both are set to always update
DNS.

Scenario

A Windows XP client machine is has an IP address of 10.1.1.1, issued
from DHCP server #1
After a reboot it collects IP address 10.1.2.1 from DHCP server #2
When I try to ping the Client the name resolves to the old address.
I check the DNS and see that the record is still 10.1.1.1, so I delete
the record and ensure that all DNS servers have no record for that
machine.
WINS has the correct address.
On the client machine I run ipconfig /registerDNS.
The DNS record is updated succesfully and and I am able to ping the
machine from the rest of the network as it resolves correctly to
10.1.2.1
Approx 2 hours later I am no longer able to ping, the client is
resolving back to the old address (10.1.1.1)
Checking DNS I see that the record has returned to it's old address.

When I check the DHCP servers I see that both have leases for the
client machine. DHCP#1 has 10.1.1.1, DHCP#2 has 10.1.2.1

I am assuming that DHCP#1 is re-registering the address with DNS and
overwriting the correct entry.

I assumed that DHCP only updates DNS when it gives out a lease, but
this would appear to show that DHCP must keep updating DNS at certain
times.

So what I'm asking is this:
If I was to change the the DHCP server to update DNS only when the
client requests would this fix the problem?
What is the schedule for DHCP updating DNS (if this is what it does),
and can this be altered?
Does the older DHCP lease have priority as it is the original owner of
the record?

BTW to fix the problem in this instance I deleted the lease on DHCP#1

Cheers in advance to all you networking gurus out there.

dave

 

[Dave Willcocks]

I'm not certain what you mean. I assume you are talking about the DNS
servers. The primary DNS server is located in another office. The
DHCP servers run DNS and hold secondary copies of the zone, they
retrieve updates from the primary.

When the DNS record is updated by DHCP it is on the primary DNS
server, and this is then replicated out to the secondaries.

Dave

 

[licknlabia]

Duh, my bad, yes, I was talking about DNS, when I should have been talking
about DHCP, sorry about that.

What is the lease time your client pc's get from your DHCP servers.

- lnl



I'm not certain what you mean. I assume you are talking about the DNS
servers. The primary DNS server is located in another office. The
DHCP servers run DNS and hold secondary copies of the zone, they
retrieve updates from the primary.

When the DNS record is updated by DHCP it is on the primary DNS
server, and this is then replicated out to the secondaries.

Dave

 

[Chris Edson [MSFT]]

The DHCP Server will only update/touch the DNS entries when it hands out the
lease, when the lease is renewed, or when the lease is deleted.
I saw mention later in the thread about a primary and a secondary DNS Server
somewhere? Is it possible that one DNS Server is 'updating' the record on
the other DNS Server?

By having the DHCP Servers only update records at client's request, you will
have the clients updating their own records, which would probably do a
little better, but you need to make sure you don't have any clients that
can't request an update...

-Chris

--
==============================
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(e-mail address removed)

This posting is provided "AS IS" with
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