2 DHCP servers 1 SBS2003 & 1 Server 2008 on the same subnet

[jajjii]

I have a dilemma when it comes to running two dhcp servers on the same subnet.

I have one Small Business Server 2003 and one Server 2008 and would like/have two DHCP servers Server01 and Server02 for fault tolerance.

SBS server (Server01) is connected to T1 and Server2008 (Server02) is connected to DSL and is the backup in case Server01 fails.

I have the IP ranges A B C D autorized on both DHCP servers with A B excluded on Server02 and C D excluded on Server01. Both are on the same subnet.

If I start the DHCP on Server01 and then start the DHCP on Server02, everything works fine and if Server01 gets shut down, Server02 takes over the clients.

Now the problem is that if I have the DHCP running on Server02 and then try to start the DHCP on Server01 (which as I mentioned above is the SBS server), DHCP on Server01 fails to start because it sees that there is already a DHCP server on the network.

I have read that if you have two DHCP servers running, one shuts down, but I have also read that you can have two DHCP server on the same subnet.

What is correct?
Why am I having the problem when I first start Server02 and then Server01, but not the other way around?

Any clarification would be appreciated.

Remy

[Big Fish]

Not a recommended set up at all and potentially very messy. Naturally you cant have 2 DHCP`s on the same physical network irrespective of the subnets they are on. If your exchange servers are receviing email via smtp this will also cause you problems as your mail will be routed by default on 25 to the internal subnet. You could POP the email instead into exchange but again thats not a best practice or recommended solution.

[jajjii]

"Not a recommended set up at all and potentially very messy."
What would be the correct setup to have fault tolerance?

For the exchange, on both Server01 and Server02, both the public NIC and the private NIC is setup with static IP, so if the DHCP fails on Server01 (Exchange) it can still recieve emails from its own internet connection.

[jajjii]

ANyone else has any comments?

[rammy]

Are you sure you broke up the reservations correctly, DHCP servers wont brodcast to each other and won't let the other know it's reservations. You can only create one scope per subnet on a single DHCP server.

Rammy

[jajjii]

Server1 (Static LAN Ip of 10.10.10.1 and its the Main server) has
Range: 10.0.0.1 - 10.0.10.255
Excluded: 10.0.10.0 - 10.0.10.255
Router:10.10.10.1
DNS:10.10.10.1

Server2 (Static LAN Ip of 10.10.10.2 and its the backup server) has
Range: 10.0.0.1 - 10.0.10.255
Excluded:10.0.0.1 - 10.0.0.255
Router:10.10.10.2
DNS:10.10.10.2, 10.10.10.1

Again, I want the Server1 to handle all the clients IP's and if Server1 goes down, Server2 should pick up and handle all the clients IP's.

[rammy]

Everything looks good there, the key here is SBS. I have heard in the past that SBS once it detects another DHCP server on it's own subnet will shut itself down, by design. Try the following it should work.

The service shutdown can be prevented by disabling DHCP rogue server detection: Let me know how it goes.

To disable DHCP rogue server detection, perform the following steps:


1. Open Registry Editor.

2. Traverse to the following location:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Dhcpserver\Pa

rameters.

3. On the Edit menu, click New->DWORD Value. Use the following parameters for the new key:

Value Name: DisableRogueDetection

Data type: REG_DWORD

Radix: Binary

Value data: 1

4. Close Registry Editor.

5. Restart the DHCP Server service.

[jajjii]

So far so good...
Thanx.