DHCP Redundant Configuration Question

April 17, 2008

Hello folks,

We've got a domain that has about 120 DHCP clients. We've got two

Win2K DCs. Until recently, all of our DHCP was handled by the second

domain controller. I modified the setup to provide some DHCP

redundancy and have some questions. Here is the current setup:

DC1

Scope: 10.1.5.60 - 10.1.5.254

Exclusions: 10.1.5.157 - 10.1.5.254

DC2

Scope: 10.1.5.60 - 10.1.5.254

Exclusions: 10.1.5.60 - 10.1.5.156

The overlapping scopes and mutually exclusive exclusion lists were set

up based on a recommendation in TechNet DHCP best practices. This

basically leaves half of range on each DHCP server. With the current

setup, each DHCP server has 97 available addresses to hand out which,

I know, is not enough for the 120 DHCP clients. The hope is that it

would be enough to get us through a crunch if one of the servers went

down. Until I can get additional IP space allocated, I will have to

live with that setup. I do have some questions about this setup that

some of you may be able to answer:

- Is there a chance a client will not be able to get an address under

normal operations? For example, if the scope on one server fills up

and the client happens to hit that server, will it get denied and give

up?

- Is there any better way of setting this up without changing the IP

range?

TIA!

MPG

April 17, 2008

Re: DHCP Redundant Configuration Question

Hello MPG,

If both servers are up and running, you will be fine, the client will search

for a DHCP server until it gets an address, doesn't matter which one. If

no server is available it will use the APIPA address. So in your case one

server must be down AND the client has to be at the half lease time, because

then it starts to renew the address. So if you are aware that one server

will be down, free the excluded range and all clients can get addresses.

Best regards

Meinolf Weber

Disclaimer: This posting is provided "AS IS" with no warranties, and confers

no rights.

** Please do NOT email, only reply to Newsgroups

** HELP us help YOU!!! http://www.blakjak.demon.co.uk/mul_crss.htm

> Hello folks,

>

> We've got a domain that has about 120 DHCP clients. We've got two

> Win2K DCs. Until recently, all of our DHCP was handled by the second

> domain controller. I modified the setup to provide some DHCP

> redundancy and have some questions. Here is the current setup:

>

> DC1

> Scope: 10.1.5.60 - 10.1.5.254

> Exclusions: 10.1.5.157 - 10.1.5.254

> DC2

> Scope: 10.1.5.60 - 10.1.5.254

> Exclusions: 10.1.5.60 - 10.1.5.156

> The overlapping scopes and mutually exclusive exclusion lists were set

> up based on a recommendation in TechNet DHCP best practices. This

> basically leaves half of range on each DHCP server. With the current

> setup, each DHCP server has 97 available addresses to hand out which,

> I know, is not enough for the 120 DHCP clients. The hope is that it

> would be enough to get us through a crunch if one of the servers went

> down. Until I can get additional IP space allocated, I will have to

> live with that setup. I do have some questions about this setup that

> some of you may be able to answer:

>

> - Is there a chance a client will not be able to get an address under

> normal operations? For example, if the scope on one server fills up

> and the client happens to hit that server, will it get denied and give

> up?

>

> - Is there any better way of setting this up without changing the IP

> range?

>

> TIA!

> MPG

April 17, 2008

Re: DHCP Redundant Configuration Question

the way you are doing it is exactly the way I have always done it and I have

never had any trouble with it. The lease peiod is 8 days by default,

meaning it renews every 4 days,...so it would probably take quite a while

(but sooner if clients are rebooted daily) to eat up all the addresses on

one DHCP if the other goes down,..but yes it would eventually happen,...the

idea is to just buy time to get the broken one fix right away. If you get

delayed on repairs just adjust the Exclusion on the remaining one to provide

a few more addresses then put it back to original aferwards.

The only difference I do is that I *always* use the entire IP Range in the

Scope based on the subnet mask, then use Exclusions to mark out the lower

Static Addresses.

It still works your way as well, so it is kind of just a preference I

suppose.

So I would have:

DC1 (with a mask of 255.255.255.0)

Scope: 10.1.5.1 - 10.1.5.254

Exclusion: 10.1.5.1 - 10.1.5.59

Exclusion: 10.1.5.157 - 10.1.5.254

DC2 (with a mask of 255.255.255.0)

Scope: 10.1.5.1 - 10.1.5.254

Exclusion: 10.1.5.1 - 10.1.5.59

Exclusion: 10.1.5.60 - 10.1.5.156

--

Phillip Windell

http://www.wandtv.com

The views expressed, are my own and not those of my employer, or Microsoft,

or anyone else associated with me, including my cats.

-----------------------------------------------------

"MPG" <mgaciarz@gmail.com> wrote in message

news:bba87c3c-59f0-4e9b-bcca-83a7bf547c7e@l64g2000hse.googlegroups.com...