Re: Determine IP address assigned to MAC

On Fri, 13 Jan 2006, in the Usenet newsgroup comp.os.linux.networking, in
article <YcednVxYQL7bVlrenZ2dnUVZ_sudnZ2d@xxxxxxxxxxx>, Ian Pilcher wrote:

>David Schwartz wrote:
>> Don't use DHCP for machines that you need to connect to. Configure them
>> statically, don't make the gateway assign the IP.
>
>That approach would be fine if the laptop never left my house. I often
>travel, however, and need to plug in to various networks. Reconfiguring
>the Ethernet interface on the laptop between DHCP and a static address
>would probably be more of a pain than having to locally run ipconfig

The way we've always handled that problem is using different runlevels
to select DHCP verses Static. Minor problem is that most modern
distributions obfuscate the hell out of the boot scripts. but it's not
an insurmountable problem. For example, look at your /etc/inittab to see
what levels are already in use. Red Hat and clones generally have runlevel
4 virtually identical to runlevel 3 (compare the links in the runlevel
directories). We simply change the "S??network link to point to a different
script that brings the network up differently. Once that is done, the
user can select the run level at boot time (LILO makes this incredibly
easy - merely pass "linux 3" or "linux 4" as the selection at the LILO
boot prompt. GRUB can do this as well, but it takes a bit more effort on
the user's part.)

Another technique is to modify the network boot script so that it asks
the user which way to go. On a laptop which won't likely be doing unattended
reboots, this is painless.

At least one other method is "profiles" - set up by some distributions. This
allows you to tailor the setup at boot time in a similar manner.

Old guy
.

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