SUMMARY: Multi Homed Host

From: Jim Jones <jrjones_at_comsource.net>
Date: Fri, 24 Nov 1995 09:41:19 -0600 (CST)

Thanks all who replied to the multi homed host question.

Below are the replies I received.

From: Greg Schlabs <schlabs_at_csc.cxo.dec.com>

  You can do this with IP alias'ing only if both ip addresses are on
    the same subnet.
    an example is:
        ifconfig ln0 16.140.64.244 netmask 255.255.255.0
        ifconfig ln0 alias 16.140.64.240

 Your aliases have to be in the same subnet as the primary
    interface subnet (172.70.101). Otherwise, the results are
    undefined and I would not be surprised to hear there are ARP
    and other problems. The system is not designed to work with
    aliases outside the subnet, which is why it's not supported.

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From: John Banghart <john_at_success.net>

Basically, you have to use 'ifconfig' with the 'alias' command. For example:

If I want my DEC to answer to an additional name of host2.my.dom, I would use
the command 'ifconfig <ether interface> alias host2.my.dom', where <ether
interface> is the interface name determined by your type of ethernet card.
Mine is tu0, yours could be different.

If you want this to work after a reboot, you have to add the above line
somewhere in your startup. I add them to /sbin/init.d/inet and that seems to
work just fine.

------
From: Eric Bennett <bennett_at_hpel.umd.edu>

Use the ifconfig command, alias option. I think you can alias only one
address at a time.

This will work for services started from inetd, which seems to understand
about multiple addresses. Since they get an already-opened socket, they
don't need to bind a socket to the alternate address.

Servers which live on a certain port, like named, probably only bind to
the primary address leaving the other unattached. In any event
they don't work at the alternate address.

-----

From: Sean Watson <swatson_at_ultrix6.cs.csubak.edu>

ifconfig tu0 -alias <new ip address>

In general, look at "man ifconfig"

-----

From: Roman Gollent <roman_at_portal.stwing.upenn.edu>

Look at the ifconfig man page and search for the heading "alias". It
will describe the exact syntax that you need.

--------
From: Fritz Kleemann <kleemann_at_informatik.uni-wuerzburg.de>

There is an option in command ifconfig:

  alias Establishes an additional network address for this interface.
            This is sometimes useful when changing network numbers and one
            wishes to accept packets addressed to the old interface.

Try ifconfig <other ip> alias

------
From: Pulak Rakshit <pulakr_at_cableol.net>

Try

#ifconfig ether_inter alias IP_address

You can put this in the /sbin/rc3.d, startup.

--------

From: Matt Theriault <knash_at_MNSi.Net>

Jim,

You must configure another network interface. I used the /usr/sbin/rcmgr
command to configure 'ln0' manually with a second IP address in a different
class for our Alpha running 3.0. I believe I remember seeing something in
the 'Guide to Network Administration' from our original OSF/1 1.3 manuals.
 Anyway, here is what I had to do (in /etc/rc.config):

/usr/sbin/rcmgr NUM_NETCONFIG="2"
/usr/sbin/rcmgr NETDEV_1="<network interface>" (same as NETDEV_0)
/usr/sbin/rcmgr IFCONFIG_1="<new IP> netmask <new netmask>"

/usr/sbin/rcinet restart to restart the network services or reboot the
machine if you can.

-------

From: "Lucien HERCAUD"_at_paribas.com
     
     Use ifconfig with the "alias" option. See the man page for ifconfig.
     
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Received on Fri Nov 24 1995 - 18:29:40 NZDT

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