split scoping

Simon Hobson dhcp1 at thehobsons.co.uk
Tue Nov 24 21:11:37 UTC 2009

Ausmus, Matt wrote:

>What are the pros and cons to using just split scoping between a 
>couple of ISC servers vs. using the draft fault tolerance mechanisms 
>built into ISC DHCPd?  1 obvious con is that DHCP leases would be 
>split between 2 different machines.  What are some others and are 
>there any pros to this setup?

I assume split scoping means running two independent servers with 
non-overlapping address allocations.

Well the first issue is that without manual intervention (and 
problems when you come to recover), both servers must have enough 
address allocation to service the entire client base (excluding fixed 
addresses which can be common across multiple servers). So if you 
have 200 clients, you need over 400 available addresses - of which 
over half will be unused.

The next problem is that if a server fails under split scoping, then 
any clients using a lease from that server WILL get a new IP address.

Simon Hobson

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