*BSD News Article 55315


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From: rstevens@noao.edu (W. Richard Stevens)
Newsgroups: comp.unix.bsd.bsdi.misc
Subject: Re: ifconfig alias command???
Date: 19 Nov 1995 00:12:44 GMT
Organization: National Optical Astronomy Observatories, Tucson, AZ, USA
Lines: 22
Message-ID: <48lsps$5ip@noao.edu>
References: <Pine.OSF.3.91.951113190701.27487B-100000@hubble.sheridanc.on.ca> <DI932r.9JF@metrics.com>
NNTP-Posting-Host: gemini.tuc.noao.edu

>    # Add routes to aliases through the loopback address (why?)
>    for i in $aliases ; do
>	echo -n "."
>	route add 198.133.164.$i $loopback >/dev/null
>    done
>    echo "."
 
Why are the route commands required ... this changed from BSDI 1.1 to
BSD/OS 2.0, with the move to the 4.4BSD-Lite networking code.  Here are
comments from my netstart file, right before the route commands for the
alias addresses:

# With 4.4BSD we must also add a local route through the loopback interface.
# Before 4.4, the code in arpresolve() went through all the IP addresses
# for the host, to check if the destination is the sender, and if so, the
# packet was sent to the loopback interface.  With 4.4 this was removed,
# and each IP address for a host must have a routing table entry that
# points to the loopback interface.  This route is automatically installed
# for the primary address for each interface (p. 708 of "TCP/IP Illustrated,
# Volume 2") but must be done manually for aliases.

	Rich Stevens