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What Is This?
~~~~~~~~~~~~~
This is an implementation of the ad-hoc link-local IP autoconfiguration
algorithm described in the IETF Draft "Dynamic Configuration of IPv4
link-local addresses", provided in the tarball, and also available at:
http://www.ietf.org/internet-drafts/draft-ietf-zeroconf-ipv4-linklocal-07.txt
[Note, zcip does not currently completely comply with this version]
Basically, it is a way of getting an IP address without manual assignment
or DHCP.
Usage
~~~~~
Refer to the man page.
Building
~~~~~~~~
This uses "libnet", from http://www.packetfactory.net/libnet;
there are other "libnet" projects, make sure you get the right one.
Version 1.0.2a works. Later versions don't.
It also uses "libpcap", from http://www.tcpdump.org;
Version 0.7.1 works.
On RedHat 7.3, you may need to modify the Makefile. Dave Brownell
says:
CPPFLAGS += -I/usr/include/pcap
On NetBSD (and probably FreeBSD) you need to apply a couple of
patches that are provided in the tarball (makearp-netbsd.patch and
zcip-netbsd.patch). These will be tested and probably applied in
the next version.
Just type "make".
Troubleshooting
~~~~~~~~~~~~~~~
Linux kernels need to support the "Socket Filtering" option (CONFIG_FILTER)
in the networking code. This is not turned on by default in standard "Linus"
kernels. If you don't have it, you'll normally get a message like:
kernel doesn't support BSD socket filters ... reconfigure
You may need to recompile your kernel to get the needed functionality - see:
http://www.linuxdoc.org/HOWTO/Kernel-HOWTO.html if you need
instructions on kernel modification.
If you get "high speed" looping, where addresses are tried and
immediately discarded (without any apparent delay), and messages like
the following:
interface: eth0 (00:40:05:DE:83:36)
probing for 169.254.41.245
avoiding collision - discarding address
address in use
probing for 169.254.117.250
avoiding collision - discarding address
address in use
probing for 169.254.24.84
...
then you probably have a kernel problem.
Copyright
~~~~~~~~~
Copyright 2002 Transmeta Corporation. This program as released under
the 3-clause BSD license, see the file "Copyright" for details.
Written by Sebastian Kuzminsky <seb@kernel.org>, with contributions from
Peter Anvin <hpa@transmeta.com>, David Brownell <david-b@pacbell.net>,
Michael Schmidt <schmidt@nue.et-inf.uni-siegen.de>.
Brad Hards <bradh@frogmouth.net> is the current maintainer.
Updates
~~~~~~~
The latest version of this program is available at
<ftp://ftp.kernel.org/pub/software/network/zcip> or from
http://zeroconf.sf.net
For more information, or if you have questions, comments or
patches, please join the ZCIP mailing list. Get info by sending
a message with just the word `help' as subject or in the body to
<zcip-request@hera.kernel.org>, or visiting:
http://linux.kernel.org/mailman/listinfo/zcip
Interoperability
~~~~~~~~~~~~~~~~
Windows ME:
When set to "Obtain an IP address automatically", WME tries to DHCP
for an address. If it fails, it looks to see if it has remembered a
previous DHCP lease. If one is found, it is used. If no old lease is
found, it'll do a variant of the zeroconf trick. So the general case
for getting WME to talk on a zeroconf network is to boot it up, run
'winipcfg', click 'Release', then click 'Renew'. When the hourglass
goes away and the 'Error' window comes up, you're good to go.
Windows 2000:
I did my tests with Windows 2000 Professional, build 2195.
Verify that "ipconfig /all" shows "Autoconfiguration Enabled: Yes"
for the relevant network interface.
W2K behaves differently from WME in terms of network configuration.
When it's set to "Obtain an IP address automatically", it'll first
try to DHCP. If that fails, it'll do the zeroconf autoconfiguration.
This is an improvement, but all is not well.
If it does not automatically do zeroconf, run "ipconfig /release",
then "ipconfig /renew". When it returns with the error "DHCP Server
unreachable", it's set up and good to go.
NOTE: W2K does not comply with the zeroconf standard draft.
The standard draft defines three distinct stages of configuration
(although it does not talk of them in these terms): 'detection',
'claim', and 'defense'. In the 'detection' phase, the machine
sends out a couple of ARP probes (ARP requests with the sender IP
address set to 0.0.0.0, indicating that the sender does not yet
have a valid address). If no ARP response is received, then the
machine moves on to the 'claim' stage and sends out some gratuitous
ARP requests with the sender IP address being the machine's desired
IP address.
W2K skips the 'detection' stage and goes straight to the 'claim'
stage. That is, the first ARP request it sends out has the sender
IP set to it's desired address. This will cause a collision defense
response from any zeroconf-standards-compliant machine configured
with that address. Normally the defending machine would send out an
ARP request defending it's ownership of the address, and the newcomer
would see the claim and try another address. However, W2K ignores
the defense and sends out second identical gratuitous ARP request.
A defending standards-compliant zeroconf implementation is required
to respond to this second collision by releasing the address and
reconfiguring.
So if W2K decides to use an address that is already in use by another
machine, W2K will effectively kick the defending machine out of
the disputed IP address, forcing it to pick a new one. This is a
relatively low probability occurrence, roughly 1 in 65000 if there
are only two machine on the network.
Windows XP:
Windows XP behaves like Windows 2000: it correctly tries to do
autoconfiguration if DHCP fails, and it does it wrong. The only
difference I've noticed between WXP and W2K in this regard is that
WXP doesn't have the 'ipconfig' program which lets the user tell
Windows to obtain an IP address automatically (this is required for
autoconfiguration to work). The user can still set this option by
going to the Network configuration section of the control panel.
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