[cisco-voip] Switch Hanging off Phone

Mike Louis MLouis at nwnit.com
Sun Sep 21 11:14:47 EDT 2008


Why is there no priority out command on this voice port. That could cause issues if you had a broadcast storm on the port from a loop on the network

________________________________
From: Todd Franklin <toddnh65 at gmail.com>
Sent: Saturday, September 20, 2008 3:48 PM
To: Mike Brooks <2xccie2b at gmail.com>
Cc: cisco-voip at puck.nether.net <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<mailto: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<mailto: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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>
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