From: Djerk Geurts (djerk@djerk.nl)
Date: Sat Jul 14 2007 - 15:09:03 ART
> With older switches, it was mandatory to have dot1q trunking.
My latest experience is from the ISR range of routers (877) which has a 4
port switch built in. in 12.4(11)T1 it worked with the default mode
(access). However going to 12.4(15) or 12.4(11)T2 and I noticed that the
normal packets didn't go through anymore. A debug packet showed no packet
coming into the access vlan.
Configuring the ports in trunk mode got everything back to normal again and
it did not break the automatic config of the cisco phone's voice vlan.
Still unsure which IOS is at fault. I did notice however that trunk
negotiation on the ISR in those two IOSes showed "Negotiation of Trunking:
Disabled" while I have no means of reconfiguring this.
Now I know the platform I'm referring to is not in the lab blueprint but it
did make me wonder how it should work. Knowing is best as testing this
during the lab is impossible. Then again one could ask to borrow a phone
from one of the voice exam ppl... ;)
Djerk
> With the 3550/3560 you don't need it.
>
> And from the 3560 configuration guide:
>
> +++++++++++++++++
> Voice VLAN Configuration Guidelines
>
> These are the voice VLAN configuration guidelines:
>
> You should configure voice VLAN on switch access ports; voice
> VLAN is not
> supported on trunk ports. You can configure a voice VLAN only
> on Layer 2
> ports.
>
> Note Voice VLAN is only supported on access ports and not on
> trunk ports,
> even though the configuration is allowed.
> +++++++++++++++++
>
> But... I've seen several types of configurations and they all work:
>
> +++++++++++++++++
> Static Access
> +++++++++++++++++
> SW1#sh runn int g0/6
> Building configuration...
>
> Current configuration : 139 bytes
> !
> interface GigabitEthernet0/6
> switchport access vlan 100
> switchport mode access
> switchport voice vlan 200
> spanning-tree portfast
> end
>
> SW1#
> +++++++++++++++++
> Static Trunk
> +++++++++++++++++
> SW1#sh runn int g0/6
> Building configuration...
>
> Current configuration : 210 bytes
> !
> interface GigabitEthernet0/6
> switchport access vlan 100
> switchport trunk encapsulation dot1q
> switchport trunk native vlan 100
> switchport mode trunk
> switchport voice vlan 200
> spanning-tree portfast
> end
>
> SW1#
> +++++++++++++++++
>
> And AFAIK, the IP Phones do not support DTP.
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf Of
> Djerk Geurts
> Sent: sabado, 14 de Julho de 2007 16:56
> To: 'Cisco certification'
> Subject: Voice vlan
>
> When configuring a voice vlan, does the interface need
> trunking enabled to
> support the voice vlan feature?
>
> If so then one should check whether the interface can
> negotiate it or not,
> if not manually enabling trunking is required. Point being
> I'm not sure it
> would be required as I assumed the access vlan would be the
> native vlan (so
> to speak).
>
> Any input welcome...
>
> --
> Djerk
> www.djerk.nl
>
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