voice and native vlan

From: gladston@br.ibm.com
Date: Tue Aug 10 2004 - 19:13:50 GMT-3


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Quoted

Richard,

I don't know why option 2 is recommended over option 1, I've seen production
configs using both methods with Cisco phones.

However, I believe you have a mistake in your options. I think the native
vlan command belongs with option 1 not option 2.

In option1, assuming a Cisco phone is used and that a PC is connected into
the back of the phone, the switch uses CDP to tell the phone which voice vlan
is in use. The phone will send voice packets to the switch using .1q frames
tagged with the specified voice vlan number. The phone will send PC packets
to the switch untagged on the native vlan. Now, when the untagged native vlan
frames hit the switch, the switch has to decide what to do with them. If
you've designed your network where all of the PCs are in vlan 1 (the default
native vlan) then you don't need the "sw native vl" command. However, I'm
sure you are more sensible and have the PCs in another vlan so you need to
notify the switch of this using the native vlan cmd. In option 1 the "sw
access vlan" command has no purpose because the port is statically configured
as a trunk port!

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If you configure:

int fa 0/0
 switchport access vlan 10
 switchport trunk encap dot1q
 switchport mode trunk
 switchport voice vlan 100

Then you do not need configure native Vlan to have data traffic goes to vlan 10. Correct?



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