[asterisk-users] Polycom IP600 + PC share same switch port withVLAN

[James Sneeringer]

Glad it worked for you. The warning is normal for Cisco switches.
Basically, the "portfast" setting disables Spanning Tree (802.1d &
friends) negotiation for the ports. It is only dangerous if you
actually connect that port to another bridging device that could
potentially have an alternate layer-2 path back to the switch (i.e. a
loop).

In the case of your Polycom phones, it is completely safe. It would
only be unsafe if you connected both ports of your phone (the uplink
*and* PC ports) into the switch, which you are unlikely to do. It's up
to you, of course. Without portfast, you're looking at about 30
seconds for STP to negotiate whenever the port bounces, during which
time higher layer protocols are unavailable. This may interfere with
CDP and DHCP, if you're using those.

-James


On Mon, Mar 3, 2008 at 8:57 PM, Lee, John (Sydney)
<John.Lee at compuware.com> wrote:
> James, thanks for the suggestion. I am just using native vlan and I did
>  what you said and I believe it works :-)
>
>  interface FastEthernet2/0/2
>   description VOIP VLAN 100
>   switchport trunk encapsulation dot1q
>   switchport trunk allowed vlan 1,100
>   switchport mode trunk
>   duplex full
>   speed 100
>
>  However, when I entered "spanning-tree portfast trunk", I received a
>  warning message which says:
>
>  "Warning: portfast should only be enabled on ports connected to a single
>   host. Connecting hubs, concentrators, switches, bridges, etc... to this
>   interface  when portfast is enabled, can cause temporary bridging
>  loops.
>   Use with CAUTION"
>
>  As the polycom phone is acting like a switch, I decided not to put that
>  option in.
>
>  ***Also, can I just confirm that with the current QOS (quality of
>  service) settings on the polycom phones, the phone should have priority
>  over the PC?
>
>  Thanks in advance.
>
>
>
>
>
>
>  > -----Original Message-----
>  > From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-
>
> > bounces at lists.digium.com] On Behalf Of James Sneeringer
>  > Sent: Saturday, 1 March 2008 9:57 AM
>  > To: Asterisk Users Mailing List - Non-Commercial Discussion
>  > Subject: Re: [asterisk-users] Polycom IP600 + PC share same switch
>  port
>  > withVLAN
>  >
>
>
> > As far as I can tell, with Polycom phones you cannot do what you're
>  > asking (which is for the PC and the phone to be in the same VLAN while
>  > the PC is connected to the phone). I don't know how they handle it
>  > when the voice frames are untagged, but they definitely won't pass
>  > tagged voice frames to the PC port:
>  >
>  >
>  http://knowledgebase.polycom.com/KanisaPlatform/Publishing/616/12526_f.S
>  AL
>  > _PUBLIC_1_2.html
>  >
>  > Your switch port is configured for untagged frames on a single VLAN
>  > (that's what "access" mode is). Polycom phones need voice and data to
>  > be on separate VLANs in order for you to use the PC port. Since
>  > Polycom phones apparently don't support the Cisco Voice VLAN feature,
>  > you need to configure the port as a trunk port, which will allow you
>  > to send multiple VLANs to the phone. The phone will take frames tagged
>  > for your designated voice VLAN, and will pass the rest on to the PC
>  > port. For example:
>  >
>  > interface FastEthernet2/0/1
>  >  switchport trunk encapsulation dot1q
>  >  switchport trunk native vlan XXX
>  >  switchport trunk allowed vlan XXX,100
>  >  switchport mode trunk
>  >  spanning-tree portfast trunk
>  >
>  > Replace XXX with whatever your PC VLAN is. Setting XXX as the native
>  > VLAN for this port will cause frames in that VLAN to be untagged for
>  > that port, which is what your PC probably expects. If it happens to be
>  > 1, then it's the native VLAN by default. The last command may or may
>  > not be available, depending on your version of IOS. If it isn't,
>  > portfast just won't work and you're just stuck with STP negotiation
>  > anytime the port bounces.
>  >
>  > -James
>  >
>
>
>
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