Discussion:
pppd and ms_dns
(too old to reply)
Chris Nelson
2006-03-31 13:08:34 UTC
Permalink
If I have Linux system with DNS configured (that is, /etc/resolv.conf
has
nameserver entries) is there any reason why my pppd ms_dns options
would list anything other than the contents of resolv.conf?
James Carlson
2006-03-31 15:02:34 UTC
Permalink
Post by Chris Nelson
If I have Linux system with DNS configured (that is, /etc/resolv.conf
has
nameserver entries) is there any reason why my pppd ms_dns options
would list anything other than the contents of resolv.conf?
Sure. The 'ms-dns' pppd option gives DNS server addresses to the peer
system using non-standard Microsoft extensions.

For any of the same reasons that two systems might not have the same
DNS server addresses configured, these might not be the same addresses
as used on the local system.

So, for, example, your local system might be a DNS server and thus
have 127.0.0.1 configured in /etc/resolv.conf, but send out some
routable address to the clients. Or your local system might be on a
DMZ and resolve against an "external" server, while clients resolve
against an "internal" one.

There are any of a number of reasons why these might differ. It
depends on your network topology and deployment.
--
James Carlson, KISS Network <***@sun.com>
Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677
Unruh
2006-03-31 17:46:09 UTC
Permalink
Post by Chris Nelson
If I have Linux system with DNS configured (that is, /etc/resolv.conf
has
nameserver entries) is there any reason why my pppd ms_dns options
would list anything other than the contents of resolv.conf?
ms_dns is a way of asking the other side for dns servers. They are stored
in /etc/ppp/resolv.conf. It is up to you (or the software) to transfer them
to /etc/resolv.conf. (I assume you are asking where Linux is the one
requesting ms_dns. )
James Carlson
2006-03-31 18:28:04 UTC
Permalink
Post by Unruh
Post by Chris Nelson
If I have Linux system with DNS configured (that is, /etc/resolv.conf
has
nameserver entries) is there any reason why my pppd ms_dns options
would list anything other than the contents of resolv.conf?
ms_dns is a way of asking the other side for dns servers. They are stored
in /etc/ppp/resolv.conf. It is up to you (or the software) to transfer them
to /etc/resolv.conf. (I assume you are asking where Linux is the one
requesting ms_dns. )
No. "ms-dns" provides addresses to the peer.

The "usepeerdns" option does what you describe.
--
James Carlson, KISS Network <***@sun.com>
Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677
Chris Nelson
2006-03-31 18:32:58 UTC
Permalink
Post by Unruh
Post by Chris Nelson
If I have Linux system with DNS configured (that is, /etc/resolv.conf
has nameserver entries) is there any reason why my pppd ms_dns
options would list anything other than the contents of resolv.conf?
ms_dns is a way of asking the other side for dns servers. They are stored
in /etc/ppp/resolv.conf. It is up to you (or the software) to transfer them
to /etc/resolv.conf. (I assume you are asking where Linux is the one
requesting ms_dns. )
No, I'm configuring a Linux server and trying to decide what to put on
the ms_dns lines of my pppd options file. I originally thought it
would be what was in that server's resolv.conf but I see now that if
the server is a DNS server, it would be the server's IP on the PPP link
(so that the PPP client would ask the server for DNS stuff) or if the
server is not a DNS server, it might be this server's resolv.conf
values (where the client would likely use this server as a default
gateway and DNS messages from the client would be forwarded).

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