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  • Two Devices w/Same IP Addr, now only one, but not recognized?

    From (PeteCresswell)@21:1/5 to All on Wed May 17 20:29:38 2017
    Got a cam server at a remote site (ExtremeSurfCam.DynDNS.org).

    One of the cams went offline, IP addr = 10.0.0.150 (assigned the cam's
    setup).

    I removed that cam and took it home, connecting it to my home LAN.

    But I had forgotten that were was already a cam on my home LAN with IP
    addr = 10.0.0.150.

    The problem cam came right up and my cam server recognized/rendered it
    and it's stream.

    OK... that cam's OK and something's goofy at the remote site.

    But after removing the problem cam from my home LAN, the "legitimate" 10.0.0.150 cam is no longer recognized: cam server does not see it,
    NetScan does not see it, and it is not pingable.

    Tried re-booting all my switches, but no joy.

    Can anybody postulate what might be going on?

    --
    Pete Cresswell
    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Char Jackson@21:1/5 to All on Tue Jun 13 14:37:28 2017
    On Wed, 17 May 2017 20:29:38 -0400, "(PeteCresswell)" <[email protected]d>
    wrote:

    Got a cam server at a remote site (ExtremeSurfCam.DynDNS.org).

    One of the cams went offline, IP addr = 10.0.0.150 (assigned the cam's >setup).

    I removed that cam and took it home, connecting it to my home LAN.

    But I had forgotten that were was already a cam on my home LAN with IP
    addr = 10.0.0.150.

    The problem cam came right up and my cam server recognized/rendered it
    and it's stream.

    OK... that cam's OK and something's goofy at the remote site.

    But after removing the problem cam from my home LAN, the "legitimate" >10.0.0.150 cam is no longer recognized: cam server does not see it,
    NetScan does not see it, and it is not pingable.

    Tried re-booting all my switches, but no joy.

    Can anybody postulate what might be going on?

    Switches have ARP tables so rebooting the relevant switch(es) or
    otherwise clearing their ARP tables so that the new (old/original) MAC
    could be learned was a good thing, but your PC has an ARP table, too.

    ARP tables are essentially a mapping of IP address to MAC address, so
    when you tried to access a device at 10.0.0.150, your PC checked whether
    that IP already had an entry in its ARP table, and it did, so it used
    the corresponding MAC address, which no longer existed because you
    unplugged that cam. If you clear the ARP table and then try to access
    that IP, ARP will broadcast a request for whoever owns that IP to
    respond, and the response will include the device's MAC address. That
    info is then populated in the ARP table. ARP entries should eventually
    time out, so your issue should have cleared up automatically after a
    certain period of time.
    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From (PeteCresswell)@21:1/5 to All on Tue Jun 13 19:37:03 2017
    Per Char Jackson:
    your PC checked whether
    that IP already had an entry in its ARP table, and it did, so it used
    the corresponding MAC address, which no longer existed because you
    unplugged that cam. If you clear the ARP table and then try to access
    that IP, ARP will broadcast a request for whoever owns that IP to
    respond, and the response will include the device's MAC address. That
    info is then populated in the ARP table. ARP entries should eventually
    time out, so your issue should have cleared up automatically after a
    certain period of time.

    That is what happened....

    Now that you have explained it, it's looking to me like I could have
    done an

    ARP -d,

    followed by something like

    ARP -s 10.0.0.150 00-aa-00-62-c6-09
    --
    Pete Cresswell
    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Char Jackson@21:1/5 to All on Wed Jun 14 05:38:05 2017
    On Tue, 13 Jun 2017 19:37:03 -0400, "(PeteCresswell)" <[email protected]d>
    wrote:

    Per Char Jackson:
    your PC checked whether
    that IP already had an entry in its ARP table, and it did, so it used
    the corresponding MAC address, which no longer existed because you >>unplugged that cam. If you clear the ARP table and then try to access
    that IP, ARP will broadcast a request for whoever owns that IP to
    respond, and the response will include the device's MAC address. That
    info is then populated in the ARP table. ARP entries should eventually
    time out, so your issue should have cleared up automatically after a >>certain period of time.

    That is what happened....

    Now that you have explained it, it's looking to me like I could have
    done an

    ARP -d,

    followed by something like

    ARP -s 10.0.0.150 00-aa-00-62-c6-09

    Normally, the 'delete' is good enough by itself, because then ARP will
    find the current IP<>MAC mapping and use it. Setting a static entry is
    normally not required, or to put it another way, setting a static entry
    is usually done with equipment that is known to not work with ARP for
    some reason. Your cams seem to work fine in that regard, so "arp -d *"
    or "arp -d 10.0.0.150" should have quickly cleared things up. Rebooting
    the relevant switch(es) was probably still helpful, as well.
    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From (PeteCresswell)@21:1/5 to All on Wed Jun 14 09:09:09 2017
    Per Char Jackson:
    Normally, the 'delete' is good enough by itself, because then ARP will
    find the current IP<>MAC mapping and use it. Setting a static entry is >normally not required, or to put it another way, setting a static entry
    is usually done with equipment that is known to not work with ARP for
    some reason. Your cams seem to work fine in that regard, so "arp -d *"
    or "arp -d 10.0.0.150" should have quickly cleared things up. Rebooting
    the relevant switch(es) was probably still helpful, as well.

    Thanks again... I've really learned something new with this one.
    --
    Pete Cresswell
    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)