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Date:      Wed, 20 Oct 1999 00:41:32 -0400 (EDT)
From:      Mike Nowlin <mike@argos.org>
To:        Sam Samalin <ssamalin@ionet.net>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: Class C hack instead of ifconfig aliases
Message-ID:  <Pine.LNX.4.05.9910200031110.29285-100000@jason.argos.org>
In-Reply-To: <380CCA4D.8A7230BB@ionet.net>

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> Is there anyway to bind a class C to an interface without a lot of
> aliases?  whats the downside of aliases?  I have a 2.2.8 hack that does
> the C, but I'd like to avoid having to port it to 3.3.

What do you mean by "bind a class C"?  Make an interface so it will
respond to incoming requests for 10.1.2.x?  ewww, yuck!

Aliases are (for me, at least) a love/hate relationship.  I have a few
machines floating around on some of my networks that use them to get
around some routing problems, and they generally work quite well for
incoming connections...  I imagine that FBSD probably has the same problem
as Digital UNIX for outgoing connections, though....

Picture, if you will, the following:

ed0   192.168.2.4  netmask 255.255.255.0  alias 208.132.36.131
route 192.168.2.0/24 -> ed0
route 0.0.0.0/0 -> gateway 208.132.36.129

Any packets sent to the gateway get 192.168.2.4 as the source, not
208.132.36.131 -- the gateway will send the packet off to the rest of the
world, where it gets immediately dropped due to the "internal use only"
source IP address.  IMHO, it should notice that it's going to a member of
the aliased network, and change the source IP to the alias address, not
the "normal" 192.168.2.4 address.

This can (usually) be fixed at the gateway with some fancy natd/ipfw
lines, but it gets ugly...

If FreeBSD does NOT have this "problem", I think we should send a copy of
it off to DEC -- I'll dig up my sequence number from the problem call I
placed a couple years ago regarding this.... :)  I finally fixed it on the
Alpha by purchasing another (really expensive - damn TurboChannel bus)
network card to handle the 2nd IP address......

mike




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