[cisco-voip] Switch Hanging off Phone

[Matlock, Kenneth L]

Are you sure that one of the ports off the linksys wasn't 'accidentally' plugged back into a wall jack (and essentially into the upstream switch)?
 
Very easy to bridge 2 VLANs doing that, and that will almost definitely affect one (or both) of them.
 
What VLAN is used for the data traffic? I believe by default most 'switch' gear uses VLAN 1 by default, and if it was spitting out STP or VTP data, that could cause serious issues, depending on your topology.
 
Ken Matlock
matlockk at exempla.org
(303) 467-4671
Network Analyst
Exempla Healthcare

________________________________

From: cisco-voip-bounces at puck.nether.net on behalf of Todd Franklin
Sent: Sat 9/20/2008 1:47 PM
To: Mike Brooks
Cc: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] Switch Hanging off Phone


Thanks Mike.  The config of the switchport:

interface FastEthernet0/4 
 switchport trunk encapsulation dot1q 
 switchport mode dynamic desirable 
 switchport voice vlan 6 
 srr-queue bandwidth share 10 10 60 20 
 srr-queue bandwidth shape  10  0  0  0 
 mls qos trust device cisco-phone 
 mls qos trust cos 
 auto qos voip cisco-phone 
 spanning-tree portfast

It really screwed around with the phones.  The data stayed ok.  

He came off from the switchport, into the 7940.  From there into the Linksys (which has a built in 4 port switch) and one of those ports he had plugged into his PC.

What do you think?

Todd


On Sat, Sep 20, 2008 at 3:38 PM, Mike Brooks <2xccie2b at gmail.com> wrote:


	What was the configuration of the switchport ?  Also was the data vlan
	affected at all or just devices on the voice vlan ?  A common issue we
	have seen with hubs plugged in is them getting mis-cabled by the
	enduser and getting looped up causing major issues on the network.  I
	do not believe the linksys devices send BPDUs.  If it was a cabling
	issue on the linksys ..then enabling bpduguard on the port will
	errdisable the port..because the port will receive its own bpdu if the
	linksys is miscabled.
	
	Also, the linksys could have been acting as a rouge dhcp server.  Not
	knowing how your network is set up or the symptoms you were
	experiencing it would be hard to tell.
	
	Just a few guesses ;-)
	
	hth,
	
	Mike Brooks
	CCIE# 16027 (R&S)
	

	On Sat, Sep 20, 2008 at 3:10 PM, Todd Franklin <toddnh65 at gmail.com> wrote:
	> Phone system went "kerflunk" yesterday.  Found a 7940 with a Linksysy
	> wireless router plugged into the PC port of the phone.  Could that have done
	> it?  I seem to remember one VAR telling me this was a grand way to take an
	> IPT network down.
	>
	> Also, is there any configuration I can add to the 3560s that would
	> "disallow" this configuration?
	>
	> Thank you!
	>
	> Todd
	
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