Anand Buddhdev <[EMAIL PROTECTED]> writes:

> I have a FreeBSD 4.7 system, with 3 ethernet cards. The first two
> are recognised as fxp0 and fxp1 and the second as em0 (intel gigabit
> card). I configured the em0 with address I then wanted
> to configure fxp0 with the address, and also connect it
> to the switch so that I can connect to the server via both addresses.
> However, FreeBSD's ifconfig command fails, and won't let me add the second
> address to the fxp0 interface. I read the manual page about ifconfig,
> and read about aliases, where it said that for aliases, I must use the
> netmask /32. When I do try to add the second address with a netmask of
> /32, it works, but it doesn't make sense to me. How is that interface
> going to to know that it is part of a /24 network if I use a /32 netmask?
> Would anyone be kind enough to explain why:
> 1. For aliases, I need the /32 mask

You don't, *unless* the address is inside of a subnet for which you
already have a route.  In that case, you obviously need to avoid

> 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 when a packet comes in for that network, there's no way to
tell which card it should go to.

I think you need to rethink your network design a bit.  If you have
different Ethernet links, you should either bridge or route between
them.  If you want to route between them, they almost always should
have distinct subnet ranges.

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