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From: brian@shift.utell.net (Brian Somers)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Multiple IP adresses with FreeBSD
Date: 30 Apr 1997 10:21:20 GMT
Organization: Awfulhak Ltd.
Lines: 46
Message-ID: <5k76f0$p26@ui-gate.utell.co.uk>
References: <5k2t8m$rtd$1@s3.iway.fr> <3366F46C.77AC@OntheNet.com.au>
Reply-To: brian@awfulhak.org, brian@utell.co.uk
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In article <3366F46C.77AC@onthenet.com.au>,
Tony Griffiths <tonyg@OntheNet.com.au> writes:
> pierre revel wrote:
>
>>
>> I suppose that I can make it with the directive 'alias' in ifconfig
>> but it doesn't work... It is not a problem with apache,
>> I'm just trying to 'ping' the server at multiple IP addresses.
>
> Alias' is the correct way of doing this. However, I don't think that
> adding an alias IP address to an Ethernet interface actually tells the
> box to respond to ARP requests. So if another host tries a 'ping' it
> will not be able to determine the MAC address of the host with the alias
> IP addresses!
>
>>
>> If anybody has an experience of this problem, any help
>> will be appreciated !
>
> In all cases that I have come across, the host containing the alias IP
> addresses is either the 'designated router' for the entire C-class, or
> there is an explicit route in the default router which points off to the
> target machine and all of the alias addresses are part of a sub-net that
> is different to the main network on the LAN. (ie. hosts on the LAN don't
> try to ARP but simply send to the default router which knowns to forward
> the packet to the virtual Web server host via an explicit route).
An arp is *always* done for machines deemed to be on the local
segment:
$ (ping -c1 ui-gate; ping -c1 auth)>/dev/null; arp -a | egrep ui-gate\|auth
ui-gate.utell.net (97.0.0.89) at 0:0:c0:f2:e1:a1
auth.utell.net (97.3.0.1) at 0:0:c0:f2:e1:a1
$ rlogin ui-gate
$ ifconfig ed1
ed1: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
inet 97.0.0.89 netmask 0xff000000 broadcast 97.255.255.255
inet 97.3.0.1 netmask 0xffffffff broadcast 97.3.0.1
ether 00:00:c0:f2:e1:a1
> Tony
--
Brian <brian@awfulhak.org> <brian@freebsd.org>
<http://www.awfulhak.org>
Don't _EVER_ lose your sense of humour !