isc-DHCP in multi-homed servers

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Here's an important tip when running a DHCP server (isc-dhcp-server on Debian) on a machine which is connected to several, physically-separated, networks:

In order to tell you dhcpd to which interfaces to listen to, edit the file "/etc/default/isc-dhcp-server" and add your DHCP-served interface names to the variable "INTERFACES".
For example, if you have 3 network cards in one computer: eth0, eth1 and eth2 - and you'd only like to serve DHCP-requests on eth1, edit the line as follows:

INTERFACES="eth1"

Then restart the dhcp-daemon:

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/etc/init.d/isc-dhcp-server restart

And verify that the changes got applied, by looking at the dhcpd process, using "ps aux":

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ps aux | grep dhcpd

This should return something like this:

root 22964 0.0 0.0 4232 2056 ? Ss 12:45 0:00 /usr/sbin/dhcpd -q eth1

As you can see, the "eth1" commandline argument shows that the DHCP-server is only listening to "eth1".

Voila!