> I have addresses and I want to run different
> services on the 2 different IP addresses. In a linux system, I do:
> ifconfig eth0 netmask
> ifconfig eth0:0 netmask
> So that I have 2 different addresses bound to the same interface.
> On FreeBSD, if I do:
> ifconfig fxp0 netmask
> ifconfig fxp0 netmask alias
> That fails.

It should fail, you should enter:

# ifconfig fxp0 netmask alias

In this situation you can ignore the /32 netmask, it will act as /24.

> The ifconfig manpage states that a nonconflicting netmaks must be used
> for the alias, and suggests to use 0xffffffff. I don't understand why,
> because I don't see why one network interface cannot have more than one
> address bound to it within the same network. If I use a /32 netmask for
> the alias address, how will the kernel respond to arp requests for that
> alias address?

arp requests for .2 will be handled properly by the kernel as if it were /24.

> > >2. Adding a second IP to a *different* network card in the same server
> > >does not work if the second IP is within the network of the first one.
> >
> > Because it breaks routing and the basic concept of IP addys and netmasks.
> > If you have two NICs on the same network, how is the kernel supposed to
> > route packets?
> I still don't understand. In a linux system I can do:
> route add -net netmask gw dev eth0
> route add -net netmask gw dev eth1

To my knowledge, this is a Linux feature.  Solaris, *BSD, and others don't let you 
specify the network interface when you add a
route.  I know for a fact under Solaris that when you have 2 interfaces which live in 
the same subnet, the interface with the lowest
numbered IP will be the interface used for outbound traffic.

> All I want to do is to have 2 different IP addresses on each of the
> different interfaces in the server, where the addresses are in the
> same network. I can do it in linux. Why can't I do it in FreeBSD?

Good question.  I'd defer this anwser to someone a bit more intimate with FreeBSD's IP 
stack and routing.

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