Re: DNS adress

[Alan Chandler <alan@chandlerfamily.org.uk>]

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On Sunday 25 May 2003 8:32 am, Piero wrote:
> I istalled a dhcp client (dhclient3) in order to let my computer
> interact with a router-switch (Netgear RP614) that contains a dhcp server.
>
> The output of "ifconfig eth0" is:
>
> eth0      Link encap:Ethernet  HWaddr 00:05:5D:AA:3B:E0
>            inet addr:192.168.0.3  Bcast:192.168.0.255  Mask:255.255.255.0
>            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>            RX packets:3 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:22 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:100
>            RX bytes:472 (472.0 b)  TX bytes:2827 (2.7 KiB)
>            Interrupt:11 Base address:0xb800
>
> This seems in order with the instructions from Netgear. Nevertheless,
> when I try to reach any Internet site, I get an answer (helas I didn't
> write it down) that lets me think that its name cannot be resolved. In
> effect, I didn't give any piece of information concerning a DNS server.

The netgear unit also uses dhcp to get the ip address of its external 
interface from your ISP.  You would normally expect as part of that process 
for it to be given the nameserver address it uses.

When it dishes up a IP address for your machine - it gives it self as the 
nameserver, but acts as a cache between you and your ISPs address.

If all is working, then dhclient on your end should then fix up so that you 
use the nameserver address (I can't remember if it writes to 
/etc/resolv.conf).  

You should be able to see what its picked up by logging on to the netgear 
router with your web browser and selecting the Router Status option.  This 
lists the nameservers it thinks your ISP has given it.

There is nothing to stop you using another nameserver.  In my setup, all the 
machines behind the netgear box (ie on my local lan) have names and therefore 
I run a nameserver on one of them to dish these out.  It then forwards 
requests to the netgear box.  Because if this, I also run a dhcp server on 
the lan and disable the netgear one.  I am therefore able to allocate 
specific IP addresses based on ethernet MAC address - something the netgear 
box can't do.  This means I cna then use port forwarding to forward specific 
ports to particular machines on my network.

[Incidently, despite buying the netgear box only a week ago, it did not come 
with the latest router software.  You can download a new version and install 
it.  It gives a few extra faciliites].

- -- 
Alan Chandler
alan@chandlerfamily.org.uk
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