How do you test your dhcpd setup?

Frank Price fprice at
Thu Jul 16 17:05:26 UTC 2015

Greetings dhcp-users,

I've recently taken over a pair of ISC DHCP 4.2.5 servers, and I'd like to
know how you test your environment -- both for troubleshooting and also for
validating config changes.  To make things concrete, let me briefly explain
our setup and then what I'd like to be able to do.

We have about 70 subnets defined, with failover peers on most of them
between our two servers.  Our network (cisco) vlan config has ip
helper-addresses which point to both servers.  Mostly we do interim-style
ddns, although there are some static host entries.

Usually everything works fine, until it doesn't, and every few months we
add a new subnet for a lab or something.  To troubleshoot, or double-check
changes,  I'd like to be able to simulate a lease request from a client.
Right now what I do is a) run dhcpd -t against the changes, and then b)
stand up a vm on the new subnet and see what happens.  It would be much
nicer to simply say "pretend you get a request from this MAC on this
subnet, and show me what you'd do."

I've tried dhcping, and it seems to require me to run it from a server
already on the subnet in question -- not quite what I want, but maybe I
just don't understand it well.

Thanks for any advice you can provide,

Frank Price | R & D Services | Lexmark International
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