2 dhcp servers and Reservation

Originally, we had one dhcp server that is running on windows 2003. IP
reservation was set up for a few network devices in DHCP.

Recently, we implemented a second dhcp server. We split off part of
the dhcp ip address range on the older dhcp server to this new one.

Am I allowed to set up reservation for those same network devices on
the second dhcp server?

Or will that cause a conflict because the reservation is already set up
on the first one?

Yes - you should create the reservation on all servers serving that subnet
even if the IP is excluded from the scope:

http://www.microsoft.com/windows2000...asp?url=/windo
ws2000/en/advanced/help/sag_dhcp_imp_bestpractices.htm

Doug Sherman
MCSE, MCSA, MCP+I, MVP

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> Originally, we had one dhcp server that is running on windows 2003. IP
> reservation was set up for a few network devices in DHCP.
>
> Recently, we implemented a second dhcp server. We split off part of
> the dhcp ip address range on the older dhcp server to this new one.
>
> Am I allowed to set up reservation for those same network devices on
> the second dhcp server?
>
> Or will that cause a conflict because the reservation is already set up
> on the first one?
>

If you have half a scope on one dhcp server and half the scope on another,
you should not create two reservations unless you don't have a issue with
which dhcp scope gets assigned.

In other words with two live dhcp servers whichever response first to the
lease request will be the active ip. For example ff your first dhcp scope is
192.168.0.5-25 and you have reserved 5-10 and your second dhcp servers scope
is 192.168.0.26-50 and you reserve 26-30 for the same devices this means a
switch could end up with either .5 or .26 for ip address.

Personally I would not do it that way since that wastes ip addresses.
Second reason is if my primary dhcp server went down I have two options. Get
the server backup before the lease expires or then manually reserve ip
address on the second dhcp server [if first is hard down I would redo the
dhcp scope to be whole again and do the reservations at that time]

I think you misunderstood. Reservations don't work that way. You should
create the same reservation IP on both servers. A DHCP server will supply a
reserved IP even from an excluded range;

http://support.microsoft.com/kb/196066/en-us

Doug Sherman
MCSE, MCSA, MCP+I, MVP


"Joshua Bolton" <(E-Mail Removed)> wrote in message
news:C828F95C-CA10-44D3-BDCE-(E-Mail Removed)...
> If you have half a scope on one dhcp server and half the scope on another,
> you should not create two reservations unless you don't have a issue with
> which dhcp scope gets assigned.
>
> In other words with two live dhcp servers whichever response first to the
> lease request will be the active ip. For example ff your first dhcp scope
is
> 192.168.0.5-25 and you have reserved 5-10 and your second dhcp servers
scope
> is 192.168.0.26-50 and you reserve 26-30 for the same devices this means a
> switch could end up with either .5 or .26 for ip address.
>
> Personally I would not do it that way since that wastes ip addresses.
> Second reason is if my primary dhcp server went down I have two options.
Get
> the server backup before the lease expires or then manually reserve ip
> address on the second dhcp server [if first is hard down I would redo the
> dhcp scope to be whole again and do the reservations at that time]