man dhcpd.conf

907_N8tiv · 08-25-2017, 01:01 AM

Just so I'm understanding this right…

Quote:

For every subnet which will be served, and for every subnet to which
the dhcp server is connected, there must be one subnet declaration,
which tells dhcpd how to recognize that an address is on that subnet.
A subnet declaration is required for each subnet even if no addresses
will be dynamically allocated on that subnet.

Some installations have physical networks on which more than one IP
subnet operates. For example, if there is a site-wide requirement that
8-bit subnet masks be used, but a department with a single physical
ethernet network expands to the point where it has more than 254 nodes,
it may be necessary to run two 8-bit subnets on the same ethernet until
such time as a new physical network can be added. In this case, the
subnet declarations for these two networks must be enclosed in a
shared-network declaration.

Note that even when the shared-network declaration is absent, an empty
one is created by the server to contain the subnet (and any scoped
parameters included in the subnet). For practical purposes, this means
that "stateless" DHCP clients, which are not tied to addresses (and
therefore subnets) will receive the same configuration as stateful
ones.

In order for DHCP automation to work… Do I have to change the configuration file for my Gateway NIC (enpls0f0), with a subnet mask and label "shared" in order for DHCP to recognize it?

Not sure if that question made sense… :-)

business_kid · 08-25-2017, 04:24 AM

I don't think the question did, but that doesn't matter.

dhcpcd is fairly good at sniffing around if you invoke it with

Code:

dhcpcd <interface>

, e.g. 'dhcpcd eth0'. It will find your dhcp server, and get you going.

It is only if that doesn't work that you need to start thinking. Subnets and vlans are separated networks over the same wire, typically to restrict access. dhcpcd can't guess those, so you have to treat it as stupid. These are typically in companies where groups like admin, R&D, and perhaps others want to have confidential traffic. But technical backup exists in companies also.

If you have a simple system, try it and record what goes wrong. If you have a complex system with subnets and/or vlans or several dhcp servers sharing the same wires, you may not be able to post externally the info required to get your query answered. We would need a fairly full description.