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Internet Software Consortium
Dynamic Host Configuration Protocol Server
Version 1.0
December 6, 1997
This is Version 1.0 of the Internet Software Consortium DHCP Server
(ISC dhcpd). In this release, support for the core DHCP and BOOTP
protocols are provided. This release currently works well on Digital
Alpha OSF/1, SunOS 4.1.4, NetBSD, FreeBSD, BSD/OS and Ultrix. It can
also be run usefully on Solaris as long as only one broadcast network
interface is configured. It also runs on QNX and Linux as long as
only one broadcast network interface is configured and a host route is
added from that interface to the 255.255.255.255 broadcast address.
If you wish to run dhcpd on Linux, please see the Linux-specific notes
later in this document. If you wish to run on a SCO release, please
see the SCO-specific notes later in this document. You particularly
need to read these notes if you intend to support Windows 95 clients.
If you are running a version of FreeBSD prior to 2.2, please read the
note on FreeBSD. If you are running HP-UX, Ultrix or Digital UNIX,
please read the notes for those operating systems below.
BUILDING DHCPD
To build dhcpd, type ``configure''. If configure can figure out what
sort of system you're running on, it will create a custom Makefile for
you for that system; otherwise, it will complain. If it can't figure
out what system you are using, that system is not supported - you are
on your own.
Once you've run configure, just type ``make'', and after a while you
should have a dhcp server. If you get compile errors on one of the
supported systems mentioned earlier, please let us know. If you get
errors on a system not mentioned above, you will need to do some
programming or debugging on your own to get dhcpd working.
LINUX
There are two big LINUX issues: Linux 2.1 ip_bootp_agent enabling and
the all-ones broadcast address.
BOOTP AGENT ENABLING
Also, some versions of the Linux 2.1 kernel apparently prevent dhcpd
from working unless you enable it by doing the following:
echo 1 >/proc/sys/net/ipv4/ip_bootp_agent
BROADCAST
In order for dhcpd to work correctly with picky DHCP clients (e.g.,
Windows 95), it must be able to send packets with an IP destination
address of 255.255.255.255. Unfortunately, Linux insists on changing
255.255.255.255 into the local subnet broadcast address (here, that's
192.5.5.223). This results in a DHCP protocol violation, and while
many DHCP clients don't notice the problem, some (e.g., all Microsoft
DHCP clients) do. Clients that have this problem will appear not to
see DHCPOFFER messages from the server.
It is possible to work around this problem on some versions of Linux
by creating a host route from your network interface address to
255.255.255.255. The command you need to use to do this on Linux
varies from version to version. The easiest version is:
route add -host 255.255.255.255 dev eth0
On some older Linux systems, you will get an error if you try to do
this. On those systems, try adding the following entry to your
/etc/hosts file:
255.255.255.255 all-ones
Then, try:
route add -host all-ones dev eth0
Another route that has worked for some users is:
route add -net 255.255.255.0 dev eth0
If you are not using eth0 as your network interface, you should
specify the network interface you *are* using in your route command.
SCO
SCO has the same problem as Linux (described earlier). The thing is,
SCO *really* doesn't want to let you add a host route to the all-ones
broadcast address. One technique that has been successful on some
versions of SCO is the very bizarre command:
ifconfig net0 alias 10.1.1.1 netmask 8.0.0.0
Apparently this works because of an interaction between SCO's support
for network classes and the weird netmask. The 10.* network is just a
dummy that can generally be assumed to be safe. Don't ask why this
works. Just try it. If it works for you, great. If not, SCO is
supposedly adding hooks to support real DHCP service in a future
release - I have this on good authority from the people at SCO who do
*their* DHCP server and client.
HP-UX
HP-UX has the same problem with the all-ones broadcast address that
SCO and Linux have. One user reported that adding the following to
/etc/rc.config.d/netconf helped (you may have to modify this to suit
your local configuration):
INTERFACE_NAME[0]=lan0
IP_ADDRESS[0]=1.1.1.1
SUBNET_MASK[0]=255.255.255.0
BROADCAST_ADDRESS[0]="255.255.255.255"
LANCONFIG_ARGS[0]="ether"
DHCP_ENABLE[0]=0
The above hack supposedly does not work on HP-UX version 9.x.
However, another hack which supposedly _does_ work on 9.x is to add
the following entry to your /etc/hosts or DNS database:
255.255.255.255 all-ones
Then modify the broadcast as follows (change to suit your
configuration, of course):
ifconfig lan0 [your ip addr] netmask [your netmask] broadcast all-ones
I would appreciate any reports as to how well this works for you.
ULTRIX
Now that we have Ultrix packet filter support, dhcpd on Ultrix should
be pretty trouble-free. However, one thing you do need to be aware of
is that it now requires that the pfilt device be configured into your
kernel and present in /dev. If you type ``man packetfilter'', you
will get some information on how to configure your kernel for the
packet filter (if it isn't already) and how to make an entry for it in
/dev.
DIGITAL UNIX
Digital Unix has one minor caveat - this version of the Internet
Software Consortium DHCP server cannot currently coexist with rarpd.
If you run dhcpd and rarpd together, dhcpd will never see any DHCP
requests, because the RARP filter has a higher priority.
FreeBSD
Versions of FreeBSD prior to 2.2 have a bug in BPF support in that the
ethernet driver swaps the ethertype field in the ethernet header
downstream from BPF, which corrupts the output packet. If you are
running a version of FreeBSD prior to 2.2, and you find that dhcpd
can't communicate with its clients, you should #define BROKEN_FREEBSD_BPF
in site.h and recompile.
SUPPORT
ISC DHCPD is not a commercial product, and is not supported in that
sense. However, it has attracted a fairly sizable following on the
Internet, which means that there are a lot of knowledgable users who
may be able to help you if you get stuck. These people generally read
the dhcp-server@fugue.com mailing list.
If you are going to use dhcpd, you should probably subscribe to the
dhcp-server and dhcp-announce mailing lists. For details, please see
http://www.fugue.com/dhcp/lists. If you don't have WorldWide Web
access, you can send mail to dhcp-request@fugue.com and tell me which
lists you want to subscribe to, but please use the web interface if
you can, since I have to handle the -request mailing list manually,
and I will give you the third degree if you make me do your
subscription manually.
PLEASE DO NOT SEND REQUESTS FOR SUPPORT DIRECTLY TO ME! The number
of people using dhcpd is sufficiently large that if I take an
interrupt every time any one of those people runs into trouble, I will
never get any more coding done.
PLEASE DO NOT CALL ME ON THE PHONE FOR SUPPORT! Answering the phone
takes a lot more of my time and attention than answering email. If you
do call me on the phone, I will tell you to send email to the mailing
list, and I won't answer your question, so there's no point in doing
it.
BUGS
This release of dhcpd does not contain support for DHCPINFORM.
Support for DHCPINFORM will be present in the next release.
DHCPINFORM is somewhat tangential to the main purpose of the DHCP
protocol, so this probably won't be a major problem for most users.
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