Download your favorite Linux distribution at LQ ISO.
Go Back > Forums > Linux Forums > Linux - Networking
User Name
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.


  Search this Thread
Old 08-25-2017, 02:01 AM   #1
LQ Newbie
Registered: Aug 2017
Location: Anchorage, Alaska
Distribution: CentOS 7 64-bit
Posts: 13

Rep: Reputation: Disabled
Question man dhcpd.conf

Just so I'm understanding this right…

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
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… :-)
Old 08-25-2017, 05:24 AM   #2
LQ Guru
Registered: Jan 2006
Location: Ireland
Distribution: Slackware, Slarm64 & Android
Posts: 16,015

Rep: Reputation: 2277Reputation: 2277Reputation: 2277Reputation: 2277Reputation: 2277Reputation: 2277Reputation: 2277Reputation: 2277Reputation: 2277Reputation: 2277Reputation: 2277
I don't think the question did, but that doesn't matter.

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


dhcp server, network, networking

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
man page is not found although $MANPATH and man.conf changed Abbraxas Linux - Newbie 3 09-05-2011 07:40 PM
slackpkg failed to find /usr/lib64/ or man.conf should be in /etc? grissiom Slackware 12 08-18-2009 03:57 AM
How to re-invoke dhcpd after changes were made to dhcpd.conf file. Azazwa Linux - Newbie 3 03-30-2009 05:44 AM
/etc/dhcpd.conf or /ltsp/dhcpd.conf ? maxsanders Ubuntu 1 07-07-2007 07:32 AM
dhcpd subnet declaration problems in dhcpd.conf vcrispo Linux - Networking 6 07-15-2005 11:32 AM > Forums > Linux Forums > Linux - Networking

All times are GMT -5. The time now is 07:46 PM.

Main Menu
Write for LQ is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration