FW: [Malvern] DHCP versus static.

[Ian Pascoe]

OK then so far I understand that all of this is around a router etc.  Now
being curious how does this work when you link one PC to another using their
network ports and the prime PC has the internet connection?

Ian

-----Original Message-----
From: malvern-bounces at mailman.lug.org.uk
[mailto:malvern-bounces at mailman.lug.org.uk]On Behalf Of Richard Forster
Sent: 27 February 2006 19:49
To: malvern at mailman.lug.org.uk
Subject: Re: [Malvern] DHCP versus static.




> On Mon, Feb 27, 2006 at 11:41:41AM +0000, 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 ?

I have DHCP. But then I have the simplest network possible (PC and
router on a /30) and clicking one checkbox to get my PC to talk DHCP was
the setup that required minimal effort.


> Do you have a dynamic network?  If not, there's no need for DHCP.  If
you're
> gonna ssh into other boxes or mount their disks then it's a pain if you've
> got DHCP running on the remote ends, you don't know where they are unless
> you're running a local DNS.  If your DHCP always gives the same addresses
to
> the same machines then it's not dynamic either and it's just a stupid way
of
> achieving a static network setup.

Simple and stupid are not quite the same ;-)

Geoff, you probably don't need it. In fact, if you are more interested
in what you do with connectivity on your LAN (local apt caches for
example so you only download Debian updates once) then just code static
addresses. If you are more interested in getting it to all auto
configure and be expandable (in theory) then by all means have a play
and get them all to use DHCP.

You could also think about setting up an IPv6 network. For kicks.


>>Can you read out the MAC number of  another host (that being invariable) ?
>>A bit like pinging, but more specific and informative.
Many ways.

arp will get you started
nmap is awesome (try nmapfe for the GUI). Type 192.168.0.* (or your
equivalent) into the target(s) section and click 'scan'. nmap will tell
you what OS your machines are running, who made your network card and
ADSL router etc, which ports are open etc etc etc.
ethereal, as Chris mentioned is also awesome. You can filter by source,
destination, traffic type etc etc. Also draws cool graphs. Very groovy
when run on a machine plugged into a switchport set to 'monitor' mode.

While you're playing, lookup how you can change your MAC address with
ifconfig.

> You mean do an equivalent to ping at the eth level instead of at IP level?
> Probably.  Have you looked at things like tcpdump and ethereal to see
what's
> happening on your network?

I think arping is closest to what Chris thought was probable.


Cheers

Rick


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