[c-nsp] Question about VLAN Trunks

[Mackinnon, Ian]

What does a show interface fa8/5 switchport show
It might be that the switchport mode trunk and switchport voice vlan
commands are incompatible

Have a look at
http://cciepursuit.wordpress.com/2009/01/01/group-study-good-explanation
-of-the-voice-vlan/

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Chris Knipe
> Sent: 20 July 2011 12:45
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Question about VLAN Trunks
> 
> Hi All,
> 
> I have a good couple of 10/100 ports configured for non-Cisco VoIP and
> during troubleshooting an issue yesterday, I noticed that our VLAN
trunks are
> not behaving as I expected.  All my ports are configured as
> follows:
> 
> interface FastEthernet8/5
>  logging event link-status
>  logging event spanning-tree status
>  logging event bundle-status
>  logging event trunk-status
>  load-interval 30
>  keepalive 30
>  mls qos trust cos
>  switchport
>  switchport trunk encapsulation dot1q
>  switchport trunk native vlan 105
>  switchport trunk allowed vlan 104,105
>  switchport mode trunk
>  switchport nonegotiate
>  switchport voice vlan 104
>  power inline never
>  storm-control broadcast level 85.00
>  no cdp enable
>  spanning-tree bpduguard enable
>  spanning-tree link-type point-to-point
> 
> When connecting a PC directly to the port and doing some tcpdumps, I
see
> traffic on the trunk port that falls outside of VLAN104 and 105...
> Shouldn't the switchport allowed vlan only allow vlan 104 and 105 to
pass via
> the port?
> 
> These are on Cisco 6500's with SUP II and MSFC II, IOS
> c6sup22-jk2sv-mz.121-26.E6
> 
> --
> 
> Regards,
> Chris Knipe
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