[cisco-voip] Re: Spanning-tree Topology Change with IP Phones

[kevin knowlen]

All,


We have narrowed the problem down to 3500 switches (3524 and 3512). 
The situation is that we want to hang computers off of the IP Phone's
PC port.  We have some 3524s in our network that we have been trying
to do this with. When we configure the interface for switchport voice
vlan XXX and switch port access vlan XXX. It doesn't work, the phone
is stuck configuring IP.  It only works if you put switchport mode
trunk on the interface.  When you do this it creates a STP topoloy
change when you plug in or unplug an IP phone into the port.  We have
tried all suggestions and all end up with the same result.  We are now
considering the separation of phones and computers on 3500 switches
where each have a physically separate port.

Is this what to expect on 3500 switches, or is there a work around? 


On Sun, 14 Nov 2004 20:44:40 -0500, Greg Arthmann
<garthmann at data-corporation.com> wrote:
>  
> 
> Kevin,
>  Spanning-tree portfast doesn't prevent a port from particpating in
> spanning-tree. What it does is signifcantly speed up the time it takes a
> port to move from blocking to forwarding.
>  So BPDU's will still be sent and recieved. Portfast should only be enabled
> on a port connected to a PC or Server, not to another switch or hub. Do you
> have any phsyical loops in your network? Plugging in an IP Phone shouldn't
> cause your spanning-tree topology to change.
>  
>  Greg Arthmann
>  Network Consultant
>  CCNP,CCDP,CIPT
>  Phone (786)554-2958
>  www.data-corporation.com
>  "Cisco Advanced Technology Partner"
>  
>  
>  
>  
>  Date: Sat, 13 Nov 2004 10:25:42 +0300
>  From: kevin knowlen <kevin.knowlen at gmail.com>
>  Subject: [cisco-voip] Switch STP problem
>  To: cisco-voip at puck.nether.net
>  Message-ID: <8a8dccee0411122325680c7877 at mail.gmail.com>
>  Content-Type: text/plain; charset=US-ASCII
>  
>  All,
>  
>  We have a problem with STP convergance.  We have a gigabit switched
>  network, using a combination of 3500, 3550, 3560 switches.  We use the
>  below switch config.  According to Cisco documentation, spanning-tree
>  port fast is susposed to prevent the voice vlan port from
>  participating in STP.  We even put bpduguard on the port.  We tested
>  the config and switches up stream still re-converge all the way up to
>  the CORE, when a IP phone is unplugged.
>  
>  Interface fa 0/2
>  switchport mode trunk
>  switchport trunk encapsulation dot1q
>  switchport voice vlan XXX
>  switchport trunk native vlan XX
>  spanning-tree portfast
>  spanning-tree bpduguard enable
>  
>  
>  --
>  1LT Knowlen, Kevin
>  
>  
>  
>  
>  
>  
>  


-- 
1LT Knowlen, Kevin