[95742] in RedHat Linux List
Re: Configuring /etc/ppp/options.cua3
daemon@ATHENA.MIT.EDU (Michael Jinks)
Tue Oct 20 23:17:49 1998
Date: Wed, 21 Oct 1998 03:14:17 +0000
From: Michael Jinks <michael@twopoint.com>
To: redhat-list@redhat.com
Resent-From: redhat-list@redhat.com
Reply-To: redhat-list@redhat.com
"C. Lamb" wrote:
>
> I) Say, my friend John wants to dial into my Linux machine using the
> phone line a ttached to my modem (
> /dev/cua3). Should I use the IP of my friend s machine as The Dns entry
> for that dial up line (/dev/cua3)??
NO. This will only lead to endless grief and plagues upon the land.
Well not really but your setup won't work.
> Or, should I choose an IP of my choice and decide that it will be
> assigned to the dial up line??
That's the right way. Remember, IP addresses belong to interfaces (like
a modem or ethernet card), not to hosts (computers). So any host needs
to have a seperate IP address for each of its interfaces.
>
> II) But how to assign a dns entry to my dial up line??
> should I just go in /etc/hosts and /etc/resolv.conf and add an entry
> like:
> 209.172.9.152 jim.allama.com ( jim.allama.com is the name of my linux
> machine).
> But that would conflict with the real IP of my machine which is
> 209.172.9.130.
Just like IP numbers, DNS names also correspond to interfaces, not to
hosts, although it often doesn't seem that way. So you should give each
of your dialup lines unique DNS names as well as unique IP numbers.
>
> Also, just telling you that there s no dns server setted on my linux
> machine. Just
> a simple linux machine connected dynamically to my ISP. with mgetty and
> IP masquerade
> on it.
In that case, you should probably be using a different set of IP numbers
than the ones you're listing, unless your ISP has specifically assigned
those IP numbers for your use. There are a few different sets of IP
numbers which are available for private use, and any other numbers
should be avoided, since you might be accidentally using somebody else's
number. Only the interface that connects to your ISP should have a
"real" IP number.
When choosing IP numbers at random, anything within the 10.x.x.x or
192.168.x.x subnets is considered legal and "non routable," which means
that packets destined for those interfaces will not be routed over the
Internet by mistake, and even if you choose an IP number that happens to
match somebody else's, it won't matter. The 209.x.x.x subnet is
definitely NOT one of those reserved subnets (I know because my office
is on it).
There are more details than this but I won't use up the bandwidth here,
as there are lots of online resources that explain this stuff better
than I could. Read the Linux Network Administrator's Guide (NAG),
available from www.linux.org and elsewhere, for detailed explanations of
setting up a facility like the one you want, and come back if you have
more questions.
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