Re: Looking for software that adds dhcp pcs to a host file

Chris F Clark <cfc@xxxxxxxxxxxxxxxxxxxx> hath wroth:

Yes, it does for one thing, but as far as I can tell the soho router
doesn't proved rarp and I want to run dhcp there because it is the
only constant on the lan, since without it, there is no lan. All the
other boxes, including the server in question, I keep it powered down
most of the time. Thus, aside from the router everything else is
transient depending upon what laptops I have brought home on any given
day and what addresses the router assigns them when I hook them in.

Therefore,, I want this software, so when sitting at this server (and
thus have it powered up), I can ssh into one of the laptops I brought
home and copy files off it onto the server. And, I don't want to have
to go to the laptop and ask it what its ip address is, since it might
not be in the same room (or even on the same floor). And, I'd like to
address the laptop by name, as that's how I know which each one is.
They're real creative names like t42p, a30p, sony, hdxpl1040 (that's a
work one and they picked the name) but I know which one each is.

If that's all you want, you're doing this all wrong. There's a
feature called "static DHCP" or "Pre-assigned DHCP" found in many
routers. These guarantee that the router will assign the same IP
address to a specific MAC address. You get all the benifits of having
a static IP address for your desktops, with central IP/DHCP
administration in the router. If you need to go to a specific known
desktop, you just point to the IP address.

The only place where this goes wrong is for laptops with an ethernet
port in both the laptop and a docking station, as well as a wireless
device. Each of these has a different MAC address and will have a
corresponding different IP address. Assigning 3 different IP
addresses for a specific laptop has caused me some grief.
Specifically, the pre-assigned DHCP table in most cheap routers is
limited in size and will not handle a large number of machines. For
example, the Dlink DI-624 can only handle 32 entries:
<http://support.dlink.com/Emulators/di624_revE/Home/h_dhcp.html>
If you need more than 32 entries, but still want to leave the power
off on anything that might be used as a DHCP server, then methinks
you're ready for a fancy new router with more features and a high
price tag.

Actually, I don't care about perfection. Duplicate entries are
interesting, because some of the laptops have cloned machine names, so
that could be an issue.

It will be a major issue if the table grows and grows with duplicate
entries every time the script is run. You'll end up with a rather
ugly huge script. The "uniq" command should fix that. Something
like:
echo "localhost 127.0.0.1" > /etc/hosts (wipe hosts file)
cat /etc/hosts.static >> /etc/hosts (restore static IP from file).
sh script.sh | uniq | sort > /etc/hosts (append results of script)

That actually, looks like a good start, I just need to revise it to
loop over the address range rather than the name in the hosts file.

Fine. I was gone for a boring lunch. I'll have some time to work on
it later tonite. It's no big deal. However, I suggest you reconsider
doing this as "pre-assigned DHCP" is a much easier way of doing it.

--
Jeff Liebermann jeffl@xxxxxxxxxxxxxxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.

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