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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Thanks all for the detailed information.<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Joe Martini [mailto:joemar2@cisco.com]
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<b>Sent:</b> Thursday, November 10, 2016 4:11 PM<br>
<b>To:</b> Ahmed Elnagar <ahmed_elnagar@hotmail.com><br>
<b>Cc:</b> Stephen Welsh <stephen.welsh@unifiedfx.com>; cisco-voip@puck.nether.net; Ryan Huff <ryanhuff@outlook.com>; Matthew Loraditch <MLoraditch@heliontechnologies.com>; Corson, Teressa <Teressa.Corson@doit.nh.gov>; Dave Goodwin <dave.goodwin@december.net><br>
<b>Subject:</b> Re: [cisco-voip] IP Phone Ports<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Cisco IP phones are designed to forward BPDUs between the network and PC port to prevent loops and let spanning tree block ports when a switch receives a BPDU it sent out. So if a user connects both ports to the same switch one port will
go into blocking state to prevent a loop. If BPDU guard is used like others said the port goes into err-disable, again preventing a loop.<o:p></o:p></p>
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<p class="MsoNormal">The only exception I know of where a loop is created was from a bug that was quickly fixed (CSCut26167). <br>
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Joe <o:p></o:p></p>
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<p class="MsoNormal">On Nov 10, 2016, at 8:56 AM, Ryan Huff <<a href="mailto:ryanhuff@outlook.com">ryanhuff@outlook.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Steven ... correct, by plugging in the PC Port to the switch as well, you would be sending BPDUs back into the switch.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">So as long as BPDU guard is enabled on the switch ports, then doing this would err-disable both switch ports (the one the PC Port and Network Port is plugged into). Pretty easy at that point
to tell who the culprit is remotely, and in person.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">= Ryan =<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span class="apple-converted-space"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> </span></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">cisco-voip
<<a href="mailto:cisco-voip-bounces@puck.nether.net">cisco-voip-bounces@puck.nether.net</a>> on behalf of Stephen Welsh <<a href="mailto:stephen.welsh@unifiedfx.com">stephen.welsh@unifiedfx.com</a>><br>
<b>Sent:</b><span class="apple-converted-space"> </span>Thursday, November 10, 2016 8:43 AM<br>
<b>To:</b><span class="apple-converted-space"> </span>Ahmed Elnagar<br>
<b>Cc:</b><span class="apple-converted-space"> </span><a href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</a><br>
<b>Subject:</b><span class="apple-converted-space"> </span>Re: [cisco-voip] IP Phone Ports</span><span style="font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">I thought that this would be prevented by default because of spanning tree/BPDU, but it’s common practice to disable spanning tree for access ports (i.e. using portfast) so that may allow the
loop to occur, so maybe just disable port-fast?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Kind Regards<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif">Stephen Welsh<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Helvetica",sans-serif">CTO<o:p></o:p></span></p>
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</span><span style="font-family:"Calibri",sans-serif"><image003.png><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">On 10 Nov 2016, at 13:35, Ahmed Elnagar <<a href="mailto:ahmed_elnagar@hotmail.com">ahmed_elnagar@hotmail.com</a>> wrote:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">That is not nice at all<span class="apple-converted-space"> </span></span><span style="font-size:11.0pt;font-family:Wingdings;color:#1F497D">L</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Did you figure out a way to prevent it from switch side?</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span class="apple-converted-space"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> </span></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">Matthew
Loraditch [<a href="mailto:MLoraditch@heliontechnologies.com">mailto:MLoraditch@heliontechnologies.com</a>]<span class="apple-converted-space"> </span><br>
<b>Sent:</b><span class="apple-converted-space"> </span>Thursday, November 10, 2016 3:34 PM<br>
<b>To:</b><span class="apple-converted-space"> </span>Ahmed Elnagar <<a href="mailto:ahmed_elnagar@hotmail.com">ahmed_elnagar@hotmail.com</a>>; '<a href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</a>' <<a href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</a>><br>
<b>Subject:</b><span class="apple-converted-space"> </span>RE: IP Phone Ports<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Yes it will create a loop. Not a fun time trying to track these things down. I’ve had some non-Cisco IP phones completely down a LAN.</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Matthew G. Loraditch – CCNP-Voice, CCNA-R&S, CCDA<br>
Network Engineer<br>
Direct Voice: 443.541.1518</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><a href="https://www.facebook.com/heliontech?ref=hl"><span style="font-size:8.0pt">Facebook</span></a></span><span class="apple-converted-space"><span style="font-size:8.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span></span><span style="font-size:8.0pt;font-family:"Calibri",sans-serif;color:#1F497D">|<span class="apple-converted-space"> </span></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><a href="https://twitter.com/HelionTech"><span style="font-size:8.0pt">Twitter</span></a></span><span class="apple-converted-space"><span style="font-size:8.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span></span><span style="font-size:8.0pt;font-family:"Calibri",sans-serif;color:#1F497D">|<span class="apple-converted-space"> </span></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><a href="https://www.linkedin.com/company/helion-technologies?trk=top_nav_home"><span style="font-size:8.0pt">LinkedIn</span></a></span><span class="apple-converted-space"><span style="font-size:8.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span></span><span style="font-size:8.0pt;font-family:"Calibri",sans-serif;color:#1F497D">|<span class="apple-converted-space"> </span></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><a href="https://plus.google.com/+Heliontechnologies/posts"><span style="font-size:8.0pt">G+</span></a></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span class="apple-converted-space"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> </span></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">cisco-voip
[<a href="mailto:cisco-voip-bounces@puck.nether.net"><span style="color:#954F72">mailto:cisco-voip-bounces@puck.nether.net</span></a>]<span class="apple-converted-space"> </span><b>On Behalf Of<span class="apple-converted-space"> </span></b>Ahmed Elnagar<br>
<b>Sent:</b><span class="apple-converted-space"> </span>Thursday, November 10, 2016 8:28 AM<br>
<b>To:</b><span class="apple-converted-space"> </span>'<a href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</a>' <<a href="mailto:cisco-voip@puck.nether.net"><span style="color:#954F72">cisco-voip@puck.nether.net</span></a>><br>
<b>Subject:</b><span class="apple-converted-space"> </span>[cisco-voip] IP Phone Ports<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">Dear all;<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">I want to know what will happen if a user connect “by mistake” both the PC port and Switch port to the network switch? Will this create a loop? Anyone tried it before?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> <o:p></o:p></span></p>
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