From: Lord, Chris (chris.lord@lorien.co.uk)
Date: Wed Aug 11 2004 - 06:12:01 GMT-3
Richard,
The clarify, the two methods (as per Cisco DQOS Book) are:
1)
int f0/1
sw mode dynamic desirable
sw access vlan 10
sw voice vlan 100
span portfast
2)
int f0/1
sw mode trunk
sw trunk encaps dot1q
sw voice vlan 100
sw trunk native vlan 10
span portfast
Regards,
Chris
-----Original Message-----
From: gladston@br.ibm.com [mailto:gladston@br.ibm.com]
Sent: Tuesday, August 10, 2004 11:14 PM
To: ccielab@groupstudy.com
Subject: voice and native vlan
====================
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!
========================
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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