RE: DHCP configuration error?
- From: Ryan Hanisco <RyanHanisco@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 14 Jan 2008 20:58:00 -0800
Hi SA,
In a High Availability configuration mode you will generally configure a
single overlapping scope with reciprocal exclusions to avoid NAK problems.
For simplicity I'll change the scopes, but you'll get the idea.
If you want the range of your addresses to be 10.1.0.0 - 10.2.254.254 with a
/16
DHCP 1
Scope 1 10.1.0.1 - 10.1.254.254 /16
Scope 2 10.2.0.1 - 10.2.254.254 /16
Exclusion 10.1.128.0 - 10.1.254.254
Exclusion 10.2.128.0 - 10.2.254.254
DHCP 2
Scope 1 10.1.0.1 - 10.1.254.254 /16
Scope 2 10.2.0.1 - 10.2.254.254 /16
Exclusion 10.1.0.1 - 10.1.127.255
Exclusion 10.2.0.1 - 10.2.127.255
In this case, I have created two scopes to allow me to manage VLANs or the
like and have split the addresses across the two servers. Whichever server
responds first will give the address, but I have to be sure to specify the IP
Helper line in the switch/ router config. The exclusions are there to
prevent a server for issuing a NAK on a lease renewal telling the client that
the range is invalid. You want it to see that the lease is excluded and
request a new one, not give up or just keep using the expired IP Address.
I could have specified one single scope for the whole range, but I prefer
not to do this as then I have to exclude the 0 and 255 addresses (you don't
have to, but I like to avoid potential inter-op problems). Normally you
would only do this in the case where you allow your network to summarize so I
prefer to break them.
Finally, you could assign one scope to each server and make it responsible
for that only. This gives you a split in load, though not actually High
Availability -- especially if your subnets have meaning for VLANs, equipment
type or something like that.
Hope this helps.
--
Ryan Hanisco
MCSE, MCTS: SQL 2005, Project+
http://www.techsterity.com
Chicago, IL
Remember: Marking helpful answers helps everyone find the info they need
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"SA" wrote:
All:.
I have two DHCP servers running on our network. We have been assigned
10.12.0.x through 10.12.7.x by the network admin.
For load balancing, I set up two servers (Windows Server 2003 R2 SP 2) with
DHCP. I set up a single scope on each server. One server assigns 10.12.0.1
through 10.12.5.255.
I noticed the other day that my server assigned 10.12.1.0 to a client. The
client is working fine... but I am surprised that that IP address was
assigned. Did I make a mistake by having only scope? I.e. should I have a
scope for each third octet and have them assigned from 10.12.x.1 to
10.12.x.254?
(Our subnet is 255.255.248.0).
Thanks,
SA.
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