Groups > alt.folklore.computers > #225952

Re: What happens to old MAC assignments?

From	Lynn Wheeler <lynn@garlic.com>
Newsgroups	alt.folklore.computers
Subject	Re: What happens to old MAC assignments?
Date	2024-07-24 14:07 -1000
Organization	Wheeler&Wheeler
Message-ID	<87plr2z64q.fsf@localhost> (permalink)
References	(5 earlier) <v7o21r$15v3i$1@dont-email.me> <v7o6kr$h2ts$1@paganini.bofh.team> <v7phef$1dsq8$7@dont-email.me> <v7qhuj$rr17$1@paganini.bofh.team> <v7r6ia$1ptki$1@dont-email.me>

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Lars Poulsen <lars@beagle-ears.com> writes:
> If the two machines have the same IP address but different MAC
> addresses, the new machine cannot take over so long as the ARP entry
> survives. Old implementations would keep the ARP table entry as long
> as it was used. Newer implementations re-arp after half the entry's
> lifetime has expired. Been there, done that as the implementor of an
> embedded IP stack.
>
> If the new machine has the same MAC address as the old one, old MAC
> level routes may survive in one or more switching hubs. Best cure for
> that is sending a broadcast from the new location. (Seen as an issue
> in a wireless network when a mobile end node moves between access
> points.)

circa 1990, when we were doing IBM's HA/CMP ... and doing IP-address
take-over (as part of failure handling) ... while (BSD) Reno/Tahoe 4.3
TCP/IP stack implementations had ARP-cache time-out, it had special code
that would save the previous MAC&IP address pair (to avoid calling
ARP-cache routine, that special save never timed-out) ... in various
client/server scenarios, some (Reno/Tahoe based TCP/IP) client use was
the same server address and therefor there was (almost) never a call to
the ARP-cache routine. We had to do special hack to do pings to clients
from different IP-address (to force a call to the ARP-cache routine)
... when take-over was involved.

-- 
virtualization experience starting Jan1968, online at home since Mar1970

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What happens to old MAC assignments? David Lesher <wb8foz@panix.com> - 2024-07-18 15:44 +0000
  Re: What happens to old MAC assignments? Gordon Henderson <gordon+usenet@drogon.net> - 2024-07-18 16:12 +0000
    Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-19 01:08 +0000
  Re: What happens to old MAC assignments? Andy Burns <usenet@andyburns.uk> - 2024-07-18 17:14 +0100
    Re: What happens to old MAC assignments? David Lesher <wb8foz@panix.com> - 2024-07-21 14:39 +0000
  Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-18 22:12 +0200
    Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-19 01:07 +0000
    Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-18 22:23 -0500
      Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-19 08:11 +0000
        Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-19 08:14 +0000
          Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-19 19:26 -0500
          Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-20 09:01 +0000
      Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-19 16:08 +0200
        Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-19 19:31 -0500
          Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-23 12:52 +0200
            Re: What happens to old MAC assignments? R Daneel Olivaw <Danny@hyperspace.vogon.gov> - 2024-07-23 14:11 +0200
              Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-24 00:21 +0000
                Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-24 00:00 -0500
                Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-24 23:46 +0000
                Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-24 21:52 -0500
                Re: What happens to old MAC assignments? R Daneel Olivaw <Danny@hyperspace.vogon.gov> - 2024-07-24 11:36 +0200
                Re: What happens to old MAC assignments? Lars Poulsen <lars@beagle-ears.com> - 2024-07-24 08:28 -0700
                Re: What happens to old MAC assignments? R Daneel Olivaw <Danny@hyperspace.vogon.gov> - 2024-07-24 20:52 +0200
                Re: What happens to old MAC assignments? Lynn Wheeler <lynn@garlic.com> - 2024-07-24 14:07 -1000
      Re: What happens to old MAC assignments? ted@loft.tnolan.com (Ted Nolan <tednolan>) - 2024-07-19 16:02 +0000
        Re: What happens to old MAC assignments? Bob Eager <news0009@eager.cx> - 2024-07-19 21:47 +0000
        Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-19 22:53 +0000
        Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-19 19:35 -0500
          Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-23 12:54 +0200
            Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-24 00:01 -0500
          Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-24 00:22 +0000
      Re: What happens to old MAC assignments? scott@slp53.sl.home (Scott Lurndal) - 2024-07-19 16:20 +0000
        Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-19 19:36 -0500
      Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-19 22:57 +0000
        Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-19 19:39 -0500
          Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-20 00:53 +0000
            Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-19 21:51 -0500
              Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-23 12:57 +0200
                Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-24 00:26 +0000
                Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-24 00:04 -0500
          Re: What happens to old MAC assignments? "Kurt Weiske" <kurt.weiske@realitycheckbbs.org.remove-hqx-this> - 2024-07-20 08:44 -0700
            Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-20 12:14 -0500
              Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-23 12:59 +0200
                Re: What happens to old MAC assignments? Ahem A Rivet's Shot <steveo@eircom.net> - 2024-07-23 12:39 +0100
                Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-23 21:40 +0200
                Re: What happens to old MAC assignments? ted@loft.tnolan.com (Ted Nolan <tednolan>) - 2024-07-23 21:38 +0000
                Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-24 11:42 +0200
                Re: What happens to old MAC assignments? Lars Poulsen <lars@beagle-ears.com> - 2024-07-24 08:29 -0700
                Re: What happens to old MAC assignments? R Daneel Olivaw <Danny@hyperspace.vogon.gov> - 2024-07-24 20:55 +0200
                Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-24 00:08 -0500
            Re: What happens to old MAC assignments? Andy Burns <usenet@andyburns.uk> - 2024-07-20 18:14 +0100
            Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-21 01:11 +0000
    Re: What happens to old MAC assignments? scott@alfter.diespammersdie.us (Scott Alfter) - 2024-07-19 15:08 +0000
      Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-19 19:41 -0500
      Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-23 13:00 +0200
        Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-24 00:10 -0500
    Re: What happens to old MAC assignments? David Lesher <wb8foz@panix.com> - 2024-07-21 14:47 +0000
      Re: What happens to old MAC assignments? Andy Burns <usenet@andyburns.uk> - 2024-07-21 16:43 +0100
        Re: What happens to old MAC assignments? Ahem A Rivet's Shot <steveo@eircom.net> - 2024-07-21 17:15 +0100
      Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-21 14:15 -0500
      Re: What happens to old MAC assignments? drb@ihatespam.msu.edu (Dennis Boone) - 2024-07-22 03:23 +0000
        Re: What happens to old MAC assignments? David Lesher <wb8foz@panix.com> - 2024-08-06 17:16 +0000
          Re: What happens to old MAC assignments? John Levine <johnl@taugh.com> - 2024-08-06 23:52 +0000
            Re: What happens to old MAC assignments? "Kurt Weiske" <kurt.weiske@realitycheckbbs.org.remove-a75-this> - 2024-08-07 08:16 -0700
              Re: What happens to old MAC assignments? John Levine <johnl@taugh.com> - 2024-08-07 16:48 +0000
      Re: What happens to old MAC assignments? Marco Moock <mm+usenet-es@dorfdsl.de> - 2024-07-23 13:01 +0200
  Re: What happens to old MAC assignments? drb@ihatespam.msu.edu (Dennis Boone) - 2024-07-18 20:43 +0000
    Re: What happens to old MAC assignments? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-07-19 01:06 +0000
      Re: What happens to old MAC assignments? drb@ihatespam.msu.edu (Dennis Boone) - 2024-07-19 01:19 +0000
    Re: What happens to old MAC assignments? Grant Taylor <gtaylor@tnetconsulting.net> - 2024-07-18 22:12 -0500
  Re: What happens to old MAC assignments? Bud Frede <frede@mouse-potato.com> - 2024-07-26 08:42 -0400
    Re: What happens to old MAC assignments? David Lesher <wb8foz@panix.com> - 2024-08-06 17:27 +0000

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