DHCP for 12000 users ???

One of my customers will implement a DHCP server cluster (two active-standby
servers) for 100 000 clients with peak traffic 12 000 clients.
Can you please advice on what type os server can be used, in terms of CPU
type, memory needed and local storage ?

Thanks a lot.

Hi anivasgr,

It is not recommended that you run DHCP using an MSCS cluster. I have seen
this done, but this isn't really a good use of the technology and there are
easier ways to get what you are looking for.

If you are using a "modern" server, you shouldn't have any real problems
with load, but I would comment that 12,000 clients is a lot for a single
subnet, so I am assuming that you will be breaking these up into a number of
sites or smaller segments. You can house these off of a pair of servers, but
if there are WAN links in play, people will usually choose to put DHCP
services at each site -- or at least at major sites. Remember that DHCP uses
broadcasts to locate a server and will take whichever one responds first.
With many sites, you would be relying on IP Helper-address commands in your
routers/ switches to direct that traffic across the WAN. This means that you
have a point of failure there.

This gives you two opportunities... You can either centralize everything
and pass that lease acquisition traffic into a pair of servers to handle it
all, or you can put DHCP services at each site and have a backup across the
WAN -- since the local segment will usually respond faster, the server
request stays local unless it can't get a response.

The key to using multiple servers, whether as a centralized/local pair or as
backup across the WAN, is to make sure that the servers have the same scopes
on each with reciprocal exclusions. If they are on the same segment serving
everyone equally, they need to be split 50/50 as they'll both take traffic.
Otherwise, if it is a failover across the WAN, I usually plan for 80/20 to
allow for some business continuity while you fix the outage.

The single scope with reciprocal exclusion is to prevent a client from
getting a NAK from the server when asking to renew an address. Instead, you
want the server to respond that the address is excluded and offer a different
one rather than just telling the client that it is invalid.

Hope this helps.

--
Ryan Hanisco
MCSE, MCTS: SQL 2005, Project+
http://www.techsterity.com
Chicago, IL

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"anivasgr" wrote:

> One of my customers will implement a DHCP server cluster (two active-standby
> servers) for 100 000 clients with peak traffic 12 000 clients.
> Can you please advice on what type os server can be used, in terms of CPU
> type, memory needed and local storage ?
>
> Thanks a lot.