
                      XROUTER INTERIM DOCUMENTATION
                      =============================

		    Dynamic Host Configuration Protocol
		    -----------------------------------

		    This revision dated: 15th July 2002



Purpose Of This Document
~~~~~~~~~~~~~~~~~~~~~~~~
"Interim" documentation is that which hasn't yet been incorporated into
the sysop manual.  It is intended to provide easily-accessible and
printable guidance for the configuration and use of new and possibly
experimental features, and is not guaranteed to be complete, accurate,
or permanent.  As development proceeds and feedback is received, the
software and this documentation may be modified.  When the development
cycle is complete, the information herein will be incorporated into the
sysop manual, and this document will be discontinued soon afterwards.

  ====================================================================


What is DHCP?
~~~~~~~~~~~~~
DHCP stands for Dynamic Host Configuration Protocol.  This is a
client-server based protocol which allows clients on a TCP/IP network
to obtain their configuration parameters from a server.  The protocol
supports the transfer of a wide range of configuration parameters,
such as the client's IP address, netmask, DNS and gateway addresses,
plus TCP/IP parameters such as MSS, but is most commonly used to
allocate dynamic IP addresses to clients.

IP addresses are "leased" to clients for a period of time, after which
the client must renew the lease.  Servers generally attempt to re-assign
the same IP address to a given client.


DHCP in Xrouter
~~~~~~~~~~~~~~~
Xrouter currently includes a DHCP client only (a DHCP server will
be included in future). The full range of configuration options is
not supported, since in most Xrouter application scenarios they are
not required.  The options currently supported are client's IP
address and lease time, DNS and gateway IP addresses.

The DHCP client is used only on Ethernet interfaces.  Lease negotiation
and renewal are completely automatic, and the sysop need not be
concerned with the process.


Do I need DHCP?
~~~~~~~~~~~~~~~
If you wish to connect Xrouter to an ISP via a cable modem e.g. to
use it as an Internet Connection Sharing router, you will probably
need DHCP if your ISP uses dynamic IP addressing.  If your ISP
assigns you a static IP address you won't need DHCP.

You will not need DHCP if your connection to the ISP is via dial-up
PPP, because dynamic IP addresses are asigned as part of the PPP log-in
process.

You will not need DHCP for normal Ethernet or amateur radio operations.


Enabling DHCP
~~~~~~~~~~~~~
In XROUTER.CFG, put "DHCP=1" in the appropriate port definition block.
There is no need to specify a port IPADDRESS because one will be assigned
by the DHCP server.  If however, a port IPADDRESS is specified (or it is
not specified but a global IP address is specified), that address will be
used for non-DHCP traffic until DHCP succeeds in leasing a (possibly
different) address.

If the global IPADDRESS is 0.0.0.0 or not specified, it will be assigned
by the first client which obtains a lease.

To disable DHCP, put "DHCP=0" in the PORT definition block, or simply
omit the keyword altogether.


(c) Paula Dowie July 2002
