Secondary DNS and DHCP

  • Thread starter Thread starter Guest
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Guest

Hi,

I'm setting up a backup DC for Active Directory, DNS, and DHCP.
I've got the Active Directory synching (by setting it up as a DC).

1) The second server automatically synced with the first when I setup the
DNS server.
I now have the second DNS server setup in my DHCP records, in case
the first server goes down completely. And have the static IP servers point
to the secondary DNS server IP. Let me know if I've setup a best practice
configuration.

2) How do I setup DHCP on the second server, so that it automatically serves
DHCP addresses when the first server dies?

I basically want maximum uptime if one of servers dies.

Do
 
There's no easy way to create a "hot-standby" DHCP server
at least without more hair than is worthwhile as DHCP isn't
at all resource intensive.

You would normally do this by creating a single scope with the same
address range on both DHCP servers, excluding each other's
address lease range to avoid conflicts. Then let both servers lease.

For example, if your DHCP addressing is 10.1.1.*,
then DHCP server "A" would have a 10.10.1.1...10.10.1.254 scope
with an exclusion for 10.10.1.128...10.10.1.254 (the range
we're going to give to "B").

DHCP server "B" would have the same scope range, but with
an exclusion for 10.10.1.1...10.10.1.127 ("A"'s range). This
prevents each DHCP server from leasing the other's addresses.
You also need to create any special range exclusions and
reservations you use identically on both servers.

If you run into problems because you can't change the existing
scope and don't want to delete it, you can usually solve the
problem by creating a superscope containing both the old and
new scopes.

As long as you've listed both DNS servers in DHCP, you should
be fine there (a "fire drill" is always recommended.) You might
want to list the DNS servers in different order in the two DHCP
servers so as to balance the load, but it usually isn't a big deal
either way in most situations when both servers are on the same LAN.

Steve Duff, MCSE
Ergodic Systems, Inc.
 
For additional information on setting up DHCP in this configuration see: 280473 How to Configure Dynamic Host Configuration Protocol Servers with Split
http://support.microsoft.com/?id=280473

Thank you,
Mike Johnston
Microsoft Network Support

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