[Ilugc] Re: A short networking tutorial

[Girish Venkatachalam]

> Reason is simple. It is stupid to have two interfaces have the same
> network address/subnet mask. Why would you do that? You can eminently
> use aliases for adding as many IP addresses in as many network ranges
> you want on a single physical interface.
> 
> The basic purpose of having multiple interfaces is to route packets
> between networks. So obviously they should belong to multiple networks.
> 

This is not always true. It is not "stupid" to do this if you know what
you are doing.

In which case you will not have to read this tutorial. :)

bridge(4) interfaces work this way.

trunk(4)  on OpenBSD work by assigning two interface the same IP
address.

carp(4) on OpenBSD again relies on this.

What is the common thread?

All of them provide redundancy/load balancing in some form. A good
example would be a wired and a wireless link. Or a costly and an
affordable tariff.  In such cases you want fail over or something
similar.


regards,
Girish