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My work setup had only one Windows 2003 DHCP Server which resides on DC01. I wanted to improve the redundancy for DHCP so I installed DHCP services on another server (DC02) which is also a DC and DNS Server.

Both DHCP servers use the same scope: xxx.xxx.172.20 to xxx.xxx.172.240. Previously DC01 administered leases for the entire scope, however we decided to implement opposite exclusions for the scope.

  • DC01 has exclusions xxx.xxx.172.111 to xxx.xxx.172.199
  • DC02 has exclusions xxx.xxx.172.21 to xxx.xxx.172.110

With the exclusions activated, no one DHCP server can supply enough leases for all our clients (approximately 140).

The first DHCP server (DC01) continues to provide DHCP leases, but the new DHCP server (DC02) doesn't give out leases even though it is authorised and active.

For testing, I took my PC off the network. We checked DC01 and its leases were at 100%. I did an ipconfig /release and ipconfig /renew however we couldn't get an IP. We only managed to get an internal 169.x.x.x IP.

This xxx.xxx.172 is a vlan, and we have setup iphelpers on the dist switch.

Are we missing anything?

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Is the DHCP helper config on the switch pointed to both DHCP servers, or just the old one? –  Shane Madden Feb 1 '12 at 7:13
    
Hi Shane, we have updated the iphelper. –  gwalker Feb 1 '12 at 21:29

2 Answers 2

We got this fixed this morning after speaking with our network guy. The iphelpers were confirmed as ok.

furhter investigation on the switch interfaces that the DHCP servers were plugged into showed they didn't have IP DHCP snooping trusetd. the following ** commands were added to the switch interfaces that the DHCP servers were plugged into.

interface GigabitEthernet0/14

description DC02

switchport access vlan 40

** ip arp inspection trust

spanning-tree portfast

** ip dhcp snooping trust

end

Thanks for the replies.

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Please remember to accept your own answer. :-) –  Nic Feb 6 '12 at 5:45

Not an answer to your question but I think this should be an answer to your actual problem, DHCP redundancy.

There is a tool I know of, "DHCP Redundancy for Windows Server 2003". This tool provides %100 redundancy by simply querying the DHCP service state of the main DHCP server and if there is a problem, starts the service on the second server. Two DHCP server's configuration is the same but in secondary server the service isn't working until primary server's service stops or unaccessible somehow.

The tool can be downloaded from http://www.c64gg.com/dhcp-redundancy/download.html . You can give it a try if you like..

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Thanks for the feedback however I want to get to root cause as to why the second DHCP server is not issuing leases. –  gwalker Feb 1 '12 at 21:10

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