RE: modem insists on overwriting my resolv.conf

[Cameron Davidson csiro au]

Hi,
	I have just been wrestling with a new ADSL setup
and I think the necessary steps depend rather a lot on
the dsl modem. So whether some of the suggestions in this thread
will work will depend strongly on the modem used.
Here's my story...
I have a dlink dsl-300+, which seems to behave in its
default configuration like a half-router/half bridge.

Specifically, to connect, it MUST receive a dhcp request,
to which it offers a 192.168... for 60 seconds,
 and tells you it is the gateway.
Then, only after you attempt to access some external site,
will it make the pppoe connection (it stores password /ID
locally). After the link is established it renews the
dhcp lease to your eth1 to be the assigned external IP
and starts to behave more like a bridge.

So, in this case, even though I have a static IP, I have to
go through the dhcp client rubbish. And dhcpcd will
overwrite /etc/resolv.conf unless it is passed a "-R" option.
Which you cause to happen in the ifup script by setting PEERDNS=no.

It seemed like a good idea at the time - a modem that handled
the pppoe encapsulation transparently. Did they say transparently?
It only seems to work with the MAC address of the eth card that had
a java-capable web browser talk to it to initialise the configuration.
Naturally there is no documentation on this.

Cameron.



> -----Original Message-----
> From: Paul Lewis [mailto:paul lewis karachi freeuk com] 
> Sent: Tuesday, 10 December 2002 08:30
> To: redhat-install-list redhat com
> Subject: Re: modem insists on overwriting my resolv.conf
> 
> 
> On 2002.12.09 17:08 Rick Stevens wrote:
> 
> > The modem itself CAN'T rewrite your resolv.conf file.  The 
> DHCP client 
> > does that, and only if it actually requests a new set of 
> DNS servers 
> > AND gets a reply to that request from the DHCP server at 
> your ISP.  So 
> > you ARE getting DNS servers from your ISP.
> 
> No actually, I am pretty sure my server is not getting them from the 
> ISP. My modem knows my ISP dns address and it knows what its own 
> internet address is but it offers a completly different set 
> of private 
> ip addresses to my pc.
> 
> > The DHCP lease is granted by the ISP's DHCP server.  The modem has 
> > NOTHING TO DO WITH IT.  It is simply the wire-level interface.  You 
> > would find the same behaviour if you used a cable (broadband) modem.
> > 
> > The most common complaint with DHCP is that it can (and often does) 
> > change your hostname when you're granted a new IP address.  
> That can 
> > cause a world of problems with the lp daemon and X.
> 
> This is an asdl modem (Eicon 2430)  with an inbuilt dhcp 
> server. On my 
> side of the modem (as opposed to the internet side) it 
> provides a fixed 
> ip address for itself 192.168.1.1 and (appears to) expect(s) to 
> assign(s) an IP address and lease to my server of 192.168.1.2. The 
> other thing that happens is my resolv.conf file is 
> overwritten with the 
> following settings;
> 
> search dsl
> nameserver 192.168.1.1
> 
> I take on board what you say about the modem not doing this. But from 
> what I can see, the modem will not permit traffic through to the 
> internet unless it has given and had acknowldedged the lease to the 
> client. It doesn't seem too bothered about the dns configuration.
> 
> What-ever way it is happening I would like to inhibit the 
> allocation of 
> the dns configuration from the modem and retain my own settings which 
> are for my local domain and my isp dns. (I know what they should be - 
> they are certanly not 192.168.1.1)
> 
> search <localdomain.net>  ;specifically chosen not to be valid on the 
> internet
> nameserver 127.0.0.1
> nameserver <isp dns address1>
> nameserver <isp dns address2>
> 
> What I initially tried to do was ignore the ip lease, and 
> just assign a 
> fixed ip address 192.168.1.2 to my server and hope that it would work 
> anyway. But while I could still interrogate the modem through telnet 
> and the web interface it seems that unless the modem itself had 
> provided the ip address (&lease) it would not permit me to 
> talk through 
> it to the internet. Enabling my eth0 interface to get its 
> address from 
> dhcp everything works except the resolv.conf gets overwritten.
> 
> Cameron Davidson has suggested that PEERDNS="no" in my 
> ifcfg-eth0 file 
> might do the trick. I havn't tried it yet but if it works it 
> would be a 
> more elegant solution than overwriting my resolv.conf file 
> every time I 
> get an ip lease from the modem.
> 
> 
> 
> _______________________________________________
> Redhat-install-list mailing list
> Redhat-install-list redhat com 
> https://listman.redhat.com/mailman/listinfo/redhat-install-lis
t
To Unsubscribe Go To ABOVE URL or send a message to:
redhat-install-list-request redhat com
Subject: unsubscribe