DHCP Backup Servers

All,

I'm restructuring 3 existing lab networks, consisting of several subnets,
overlaying a AD Domain. At the moment each subnet has its own DHCP server
(some MS based, other UNIX based). I was thinking of condensing that to one
DHCP server, and adding relay agents on each subnet.

If I do that though, I have a potential single point of failure in having
only one DHCP server. So how can I setup a "backup" DHCP server?

My other idea is to replace the existing DHCP servers with Microsoft
products, then use the MMC to attach to each.

Whats the best method??

Adrian

Just build a second DHCP with identical Scope settings. Then use Exclusions
on each so that one gives out half the addresses and the other gives out the
second half of the addresses. If one dies, you just remove the Exclusions on
the remaining one so it can give out all addresses. Return the Exlcusion
back to the way they were when the bad one is fixed.

"Adrian Marsh" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> All,
>
> I'm restructuring 3 existing lab networks, consisting of several subnets,
> overlaying a AD Domain. At the moment each subnet has its own DHCP server
> (some MS based, other UNIX based). I was thinking of condensing that to
one
> DHCP server, and adding relay agents on each subnet.
>
> If I do that though, I have a potential single point of failure in having
> only one DHCP server. So how can I setup a "backup" DHCP server?
>
> My other idea is to replace the existing DHCP servers with Microsoft
> products, then use the MMC to attach to each.
>
> Whats the best method??
>
> Adrian
>
>

I thought with DHCP relay, that you had to specify the specific DHCP server
to use... Can you specify more than one server??


"Phillip Windell" <@.> wrote in message
news:(E-Mail Removed)...
> Just build a second DHCP with identical Scope settings. Then use
Exclusions
> on each so that one gives out half the addresses and the other gives out
the
> second half of the addresses. If one dies, you just remove the Exclusions
on
> the remaining one so it can give out all addresses. Return the Exlcusion
> back to the way they were when the bad one is fixed.
>
> "Adrian Marsh" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
> > All,
> >
> > I'm restructuring 3 existing lab networks, consisting of several
subnets,
> > overlaying a AD Domain. At the moment each subnet has its own DHCP
server
> > (some MS based, other UNIX based). I was thinking of condensing that to
> one
> > DHCP server, and adding relay agents on each subnet.
> >
> > If I do that though, I have a potential single point of failure in
having
> > only one DHCP server. So how can I setup a "backup" DHCP server?
> >
> > My other idea is to replace the existing DHCP servers with Microsoft
> > products, then use the MMC to attach to each.
> >
> > Whats the best method??
> >
> > Adrian
> >
> >
>
>

"Adrian Marsh" <(E-Mail Removed)> wrote in message
news:uQJK$(E-Mail Removed)...
> I thought with DHCP relay, that you had to specify the specific DHCP
server
> to use... Can you specify more than one server??

It is done on the LAN Router. On our router, yes, you can give it a List of
IP#s to forward to. On some routers you have have it forward to the subnet
which then allows any DHCP runing on that subnet to be found.

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

> Just build a second DHCP with identical Scope settings. Then use
> Exclusions on each so that one gives out half the addresses and the
> other gives out the second half of the addresses. If one dies, you
> just remove the Exclusions on the remaining one so it can give out
> all addresses. Return the Exlcusion back to the way they were when
> the bad one is fixed.

Well Phil, an alternate solution (if possible) would be changing the
netmask to double the subnet address space, then setting up the
two DHCP servers to serve one half each one, this way if one of the
servers goes down, the other one won't need manual intervention
since its address space will suffice for all the clients; another way
although more complex ... is to install a monitoring software on the
"backup" DHCP such s/w (it may even be a scheduled script) will
monitor the primary DHCP and if it goes down will start the DHCP
service on the backup machine