Question about failover with ISC DHCP

[Olivier Nicole]

Hi Luis,

> I am looking to replace my current DHCP server with the ISC.  Right now
> I have to servers which are working with split scopes.   Some of my
> schools need over 600 IP's,  so I have the school with a 255.255.240.0
> which give them 16 Class C, network, so to avoid conflicts I assign the
> 3 lower to one server and the 3 highest to the other.=20

This part is really not clear: you have 16 class C, and you assing 3
and 3? What about the 10 others?

> Now comes the question, in the following section there is a split of
> 128.  If I give a range of 3 class C's do I set this value to 128 or
> (128*# Class C Networks)? =20

Fron man dhcpd.conf

       The split statement

         split index;

         The  split statement specifies the split between the primary and sec-
         ondary for the purposes of load balancing.   Whenever a client  makes
         a DHCP request, the DHCP server runs a hash on the client identifica-
         tion.   If the hash comes out to less than the split value, the  pri-
         mary  answers.    If it comes out to equal to or more than the split,
         the secondary answers.   The only meaningful value is  128,  and  can
         only be configured on the primary.

This is certainly not giving much information, but they suggest you
use 128, so try with 128 first.

I'd suggest that you let the load balancing run for a while, then you
can see how many clients are served by each DHCP server and you may
try to fine adjust the split value.

I have been using fail-over while I was preparing a new DHCP server
recently (so the clients could start using the new server and the
leases were transfered from the old to the new machine) and it was
really seamless.

Best regards,

Olivier