DHCP

[HenkR]

Is it ok to have 2 DHCP servers running?

for example
server1: scope: 192.168.1.10 -> 192.168.1.50
server2: scope: 192.168.1.51 -> 192.168.1.90

 

[djtech2k]

Yes

 

[HenkR]

I asked because on another forum I read that it was not a good idea, but I don't know why...

 

[FloDiggs]

Typically, when you are using two DHCP servers, you operate under the 80/20 rule. This ixplains it pretty well.

http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/cnet/cncb_dhc_ogjw.mspx?mfr=true

 

[Spirit]

80/20 only works if the 20 is enough for you purposes either load balancing or redundancy.

You might have to create 2 ranges large enough for each dhcp server to allow 100% of the clients to get their leases.

Iain

 

[WhoKilledKenny]

server1: scope: 192.168.1.10 -> 192.168.1.50
server2: scope: 192.168.1.51 -> 192.168.1.90

All the advice your getting is good, so my .02

From what you have shown, this is how I build my scopes.

Server 1:
Scope 1 - 192.168.1.1 -> 192.168.1.254
Ip Exclusions - 192.168.1.1 -> 192.168.1.9; 192.168.1.51 -> 192.168.1.254

Server 2:
Scope 2 - 192.168.1.1 -> 192.168.1.254
IP Exclusions - 192.168.1.1 -> 192.168.1.50; 192.168.1.91 -> 192.168.1.254

The reason I do my scopes this way is that using exclusion ranges allows for more flexibility with scope changes.

The 80/20 split rule is a Microsoft rule and should work fine. The only time I've seen issues are with short lease times like one-day. The standard 80/20 rule and the default of lease of 8 days is plenty.

I understand spirit's thinking regarding scope redundancy but I just disagree with the logic. A lease time of 8 days would allow plenty of time to restore and in worse case rebuild a DHCP server. Clients will maintain their IP Address while resolving the issue, at least maintain them until 100% of the lease expires.

Just to keep the terminology from getting confusing, DHCP is not Load Balanced. You can cluster DHCP if high avail is required.