[cisco-voip] IP Phone Ports

[Ryan Huff]

Steven ... correct, by plugging in the PC Port to the switch as well, you would be sending BPDUs back into the switch.


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.


= Ryan =



________________________________
From: cisco-voip <cisco-voip-bounces at puck.nether.net> on behalf of Stephen Welsh <stephen.welsh at unifiedfx.com>
Sent: Thursday, November 10, 2016 8:43 AM
To: Ahmed Elnagar
Cc: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] IP Phone Ports

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?

Kind Regards

Stephen Welsh
CTO

[cid:CBBF0493-235C-43D2-A874-9FB3D95AF598 at b2.unifiedfx.com]

On 10 Nov 2016, at 13:35, Ahmed Elnagar <ahmed_elnagar at hotmail.com<mailto:ahmed_elnagar at hotmail.com>> wrote:

That is not nice at all :(

Did you figure out a way to prevent it from switch side?

From: Matthew Loraditch [mailto:MLoraditch at heliontechnologies.com]
Sent: Thursday, November 10, 2016 3:34 PM
To: Ahmed Elnagar <ahmed_elnagar at hotmail.com<mailto:ahmed_elnagar at hotmail.com>>; 'cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>' <cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>>
Subject: RE: IP Phone Ports

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.

Matthew G. Loraditch - CCNP-Voice, CCNA-R&S, CCDA
Network Engineer
Direct Voice: 443.541.1518
Facebook<https://www.facebook.com/heliontech?ref=hl> | Twitter<https://twitter.com/HelionTech> | LinkedIn<https://www.linkedin.com/company/helion-technologies?trk=top_nav_home> | G+<https://plus.google.com/+Heliontechnologies/posts>

From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Ahmed Elnagar
Sent: Thursday, November 10, 2016 8:28 AM
To: 'cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>' <cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>>
Subject: [cisco-voip] IP Phone Ports

Dear all;

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?


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