[Malvern] DHCP versus static.

[Stefan Szwarnowski]

On Monday 27 February 2006 11:41, Geoff Bagley wrote:
> I am still trying to get a better understanding of Ethernet.
>
> Do you guys  prefer to use Static IP addresses on your LAN,  or do you
> prefer DHCP ?
>
> Can you read out the MAC number of  another host (that being invariable) ?
> A bit like pinging, but more specific and informative.
>
> By the way,  some outfit in Hunan, China,  keeps probing my system
> (unsuccessfully) !

We're using DHCP entirely on our LAN with mixture of static and dynamic 
assignments. ISC dhcpd running on an old PC is used as the DHCP server. 
Desktop computers get a static assignment through an entry in /etc/dhcpd.conf 
with their MAC address and hostname/IP. There is also a dynamic IP pool and 
this has been setup for Wireless LAN users (mostly the neighbours :-).

You can determine a machines IP address by pinging it as usual and then 
running /sbin/arp. This will get you the kernel's IP<->MAC address table. You 
might want to try the 'arping' package; this functions in a similar way to 
the standard ping application but uses ARP instead of ICMP.

Here's an example of pinging a host on my LAN. Unlike the '/sbin/arp' method 
above, you will need to run this as root though.

----------
# arping access-rtr
ARPING 192.168.0.1
60 bytes from 00:01:42:33:24:1e (192.168.0.1): index=0 time=1.501 msec
60 bytes from 00:01:42:33:24:1e (192.168.0.1): index=1 time=1.507 msec
60 bytes from 00:01:42:33:24:1e (192.168.0.1): index=2 time=1.557 msec
60 bytes from 00:01:42:33:24:1e (192.168.0.1): index=3 time=1.506 msec

--- 192.168.0.1 statistics ---
4 packets transmitted, 4 packets received,   0% unanswered
----------

If you're using debian 'apt-get arping' otherwise get it here 
http://freshmeat.net/projects/arping/

Hope that helps,

Stefan.