Re: laptop,dhcp,fixed addresses

[Matt Price <matt.price@utoronto.ca>]

hey alan,

thanks again!  I'm learning a lot. questions keep coming though, just 
stop answering when you get fed up I guess...

Alan Chandler wrote:
> On Thursday 14 April 2005 02:10, Matt Price wrote:

> Just so that you are not totally confused, my main server has 192.168.0.20 as 
> its main ip address, but also (on the same ethernet card) has 192.168.0.30 
> and 192.168.0.39 addresses.  These are created with additional stanza's 
> in /etc/network/interfaces (heres a snippet to show what I mean)
>
> iface eth1 inet static
>         address 192.168.0.20
>         netmask 255.255.255.0
>
> iface eth1:0 inet static
>         address 192.168.0.30
>         netmask 255.255.255.0


hey, didn't know you could do that.  interesting.

> > > ; below are allocated via dhcp because of compatibility at university
> > > eeyore  IN      A       192.168.0.23    ; Emily's Portable
> > > piglet  IN      A       192.168.0.24    ; Sarah's Portable
> > > ; Special for work portable - must be allocated by dhcp because of
> > > ; Work - it uses the mac address to find this address.
> > > rabbit  IN      A       192.168.0.25
> >
> > these I don't get.  If they IP's are allocated via dhcp, how do you know
> > in advance that they will get the address you assign here?  Are you
> > doing some kind of magic with the dhcp server?
>
>
> Yes - see my dhcp file - it uses the mac address of the ethernet card to 
> detect which machine they are.  Some of the portables have two addresses so I 
> have to play some silly tricks to cover them both.  Note, this also 
> contains a way of setting hostnames.

ah, very nice.  I am going to try and set up something precisely 
parallel -- still haven't been near enough to the classroom to actually 
DO IT -- but soon I hope.  meanwhile, a question:

I'm intrigued by the ocmments in your dns files like:
; Special for work portable - must be allocated by dhcp because of
; Work - it uses the mac address to find this address.

Do you have some trick that enables you to move between locations 
without changing the network interface?  On my laptop I have the 
following ocnfiguration:

# The first network card - this entry was created during the Debian 
installation
iface dynamic inet dhcp

# when connecting via another laptop, use dhcp;
# otherwise use the static configuration
auto eth0
 iface eth0 inet static
        address 192.168.2.198
         netmask 255.255.255.0
        broadcast 192.168.2.255
        gateway 192.168.2.1

 iface net-sidsmith inet static
        address 128.100.34.173
        netmask 255.255.255.0
        network 128.100.34.0
        broadcast 128.100.34.127
        gateway 128.100.34.1


and then this little script I wrote brings one up and the other down:

ifdown -a
ifup eth0=net-sidsmith
ifup lo

do you have a trick that somehow avoids such manipulation?

m