RE: tlug: More IP addresses

[Frank Bennett <bennett@example.com>]

On Tue, 8 Dec 1998, Stephen Carter wrote:

> Is there a good fac on how to set up IP masquerading, especially how to
> incorporate a dynamically allocated address of the dial-up ppp sort?  The
> kind of think all the ISPs wish we wouldn't do?

If you have a Linux box with installed documentation handy, it's
probably in your machine waiting for you.  Under TL or RedHat, try:

  /usr/doc/HOWTO/mini/IP-Masquerade

Think carefully before going the dynamically-allocated route.  The only
circumstance in which it does anything for you is when you have to
allocate real-world IP addresses that have been allocated to you for
distribution by the powers that be, and you have more users to service
than you have IP addresses to hand.  If that doesn't describe your
situation, then static assignment is a better choice; it makes it simpler
to track down the source of trouble when someone's machine goes crazy and
starts piping hazardous rubbish to your server.

In particular, if you are using masquerading to subnet, every connection
from a subnetted machine will appear to the Internet to have originated
from the masquerading firewall machine itself.  Behind the masquerading
firewall, you will use private addresses in the local range for
firewall-client communications.  I forget the exact starting-point of the
range, but there are 64,000 addresses in it, so you're not likely to run
out.  :) 

My two bits' worth, anyway.

Note that there is one limitation to a masquerading setup; masquerading
only works for outbound connections, so you won't be able to station a
public server behind the firewall -- public servers would have to run on
the firewall machine itself.

Cheers,
---
Frank G Bennett, Jr         @@
Faculty of Law, Nagoya Univ () email: bennett@example.com
Tel: +81[(0)52]789-2239     () WWW:   http://rumple.soas.ac.uk/~bennett/



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