[cisco-voip] "switchport" command behavior on 3500XL

[Lelio Fulgenzi]

here's what we have. it's done us well. we had (and are still working out I believe) some issues with QoS on these older switches. some of the guys on the team investigated and determined the allowed vlans should be modified for a more efficient/secure delivery. vlan 129 and 131 are our mgmt networks, that's why there were deleted. i'm sure we could have gone further and only allowed 1 (default, can't remove) the voice and data vlans and (1000-1005, can't remove these either i think).


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interface FastEthernet0/3
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 226
 switchport trunk allowed vlan 1-128,130,132-1005
 switchport mode trunk
 switchport voice vlan 938
 switchport priority extend cos 0
 spanning-tree portfast

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Lelio Fulgenzi, B.A.
Network Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
"I had a coffee and Coke at lunch today...and now, I've got more jitter than an
IP phone on a long haul 10base2 connection"                                           LFJ
  ----- Original Message ----- 
  From: Brian Feeny 
  To: cisco-voip at puck.nether.net 
  Sent: Saturday, August 27, 2005 1:34 AM
  Subject: [cisco-voip] "switchport" command behavior on 3500XL



  I have a question regarding the behavior of some "switchport"  
  commands on the 3500XL vs. other cisco switches.

  On a 4000 (IOS) you can do:

  switchport trunk encapsulation dot1q
  switchport access vlan 100
  switchport voice vlan 200

  And that will allow you to:

  connect a regular device, and it will use vlan 100
  connect a cisco phone and it will trunk, placing the phone into vlan  
  200, and device connected thru the phone into vlan 100

  But on a 3500XL, which supports those same commands, it apparently  
  does not behave that way.  You have to do:

  switchport trunk encapsulation dot1q
  switchport mode trunk
  switchport access vlan 100
  switchport voice vlan 200

  which then allows the phone to work as you would expect, but a PC  
  connected directly to the switch will not work so you have
  to add the native vlan:

  switchport trunk encapsulation dot1q
  switchport trunk native vlan 100
  switchport mode trunk
  switchport access vlan 100
  switchport voice vlan 200

  which once you have done that, doesn't even make sense to have  
  "switchport access vlan 100", so end up with:

  switchport trunk encapsulation dot1q
  switchport trunk native vlan 100
  switchport mode trunk
  switchport voice vlan 200

  I am just trying to nail down what config I should use to allow the  
  port to be used directly by a device such as a PC, and also allow it  
  to trunk to a cisco phone that would carry voice/data vlans.  It  
  seems these commands change alot as IOS gets updated.  What is the  
  correct configuration to do what I am wanting on the 3500XL?

  Brian

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