DHCP Fault-Tolerance on Different subnets

[Guest]

Hi,

I would like to implement 2 DHCP servers at 2 different sites and obtain
fault tolerance at the same time.

Sites A and Site B will be as follows:
Site A - Subnet A is 172.16.X.X/16
Site B - Subnet B is 192.168.0.X/24
My Routers are Bootp.

Superscopes will be as follows:
superscope on DHCP server1 (SiteA):
scope1 :172.16.0.1 - 172.16.0.254
scope2 : 192.168.0.1 - 192.168.0.50

superscope on DHCP server2 (SiteB):
scope1 : 192.168.0.51 - 192.168.0.254
scope2 : 172.16.1.1 - 172.16.1.254

Is there a risk that DHCP clients at Site A receive IP address 192.168.0.X?
Do I need to put in any exclusions?
I would like to know if my design is correct and if I am acheiving
fault-tolerance.

thks and rgds

 

[Phillip Windell]

Is there a risk that DHCP clients at Site A receive IP address 192.168.0.X?

Yes.

Do I need to put in any exclusions?
No.

I would like to know if my design is correct and if I am acheiving
fault-tolerance.

Don't use Superscopes,...that isn't what they are for. Superscopes take all
the small scopes you add to them and make them behave as one single large
scope,...this is the opposite of what you want.

What you want is two separate single normal scopes,..one for each subnet.
Use the entire address range in each scope. configure both DHCP servers
exactly identically. Then use Exclusions on each one so that each one gives
out half of the available addresses. Then if one DHCP box geos down you
simply remove the Exclusion on the remaining one so that it can give out all
the addresses. When the first one is repaired, put the Exclusions back
again.

The location physical of them is up to you but they will do the same thing
wherever you put them. The "reachability" of them is determined by the
routing device between the subnets and how sophisticated it is about
forwarding DHCP "queries". The "reachability" does not depend on the DHCP
Servers themselves.