Summary: DHCP

From: Robert Borowicz <>
Date: Fri Dec 07 2001 - 11:23:23 EST
Here is a Summary of my DHCP Question. Primarily I wanted to know about
redundancy of DHCP and LDAP services. Thanks to:

Stephen Harris
Alan "dwarf"
Ken Germann
Phil Brutsche
Dan Lowe

****************** My Original Question ******************

I'm begininng my research into moving DNS, DHCP, and LDAP services from our
primary E450 NFS server onto 4 Netra's we are about to get. I know DNS offers
a secondary mechanism, but does DHCP and LDAP? IE: Can we have two DHCP
service processes running at the same time and have them dynamically
We want 2 of the Netra's to be primary DNS/DHCP/LDAP and the other two to be

****************** END *******************************

***************** Ans 1 *******************************

> a secondary mechanism, but does DHCP and LDAP? IE: Can we have two DHCP

LDAP is designed to have replica servers.  That's no problem.  Well, relative
to the headache LDAP actually is :-)

DHCP is harder; by default no you can not have two servers serving the same
scope.  If you have enough free addresses (eg if you are serving out 10.*
addresses) then I generally configure DHCP server 1 to serve half the scope
and server 2 to serve the other half.  Both work all the time.  If one dies
then you still have the other one serving valid addresses.

Commercial products, like Quadritek/Lucent QIP have backup DHCP abilities
as far as I can tell.

**************** End Ans 1 *****************************

****************  Ans 2 ********************************

Generally with LDAP you have one master and can have one or more
consumers (sometimes referred to as slaves).  The changes are always
made on the master but those changes get reflected on consumers, and
lookups against any of them should result in the same returned data.
How to do that specifically depends on what server you're using, and
should be in the server docs.

***************** End Ans 2 ********************************

****************** Ans 3 **********************************

Not hard to do.  If your DHCP scope is for 255 address's you could put
128 on one server and 128 on the other, then if one goes away they other
can still serve up IP address's.  For LDAP, use iDAR, iPlanet Directory
access router or any other load balancer and keep the data in sync.

**************** Enb Ans 3 *********************************

Robert K. Borowicz
Unix/Network Admin.
O: 512-936-2401
P: 512-899-7360
Received on Fri Dec 7 16:23:23 2001

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