Trunk between cisco switch 2960 and 3com switch 4500

Unanswered Question

I am having the problem to do the trunking between cisco switch 2960 and 3com switch 4500? Seems both of them cannot communicate with each other. Anyone can help? Below is the command from both of the switches.

Cisco :

switchport access vlan 50

switchport mode trunk


port link-type trunk

port trunk permit vlan 50

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Jerry Ye Sun, 08/24/2008 - 08:07
User Badges:
  • Cisco Employee,


You have to define trunk encapsulation on the port:

switchport trunk encapsulation dot1q

Also, "switchport access vlan 50" is not necessary since it is uses for access port, not on trunk port.



alexander76 Mon, 08/25/2008 - 07:12
User Badges:


first you define this Cisco port as an uplink port to the 3Com Switch and put .1q encapsualation on it:

- switchport mode trunk

- switchport trunk encapsulation dot1q

Then you define the vlans which shall run over this port (not necessary when all vlans shall be allowed):

- switchport trunk allowed vlan add 1,2,10

or you say allow all vlans except...

- switchport trunk allowed vlan except 1,2,10

maybe you should define speed and duplex on both port statically - not auto!

Greetz from Germany ;)

Jerry Ye Mon, 08/25/2008 - 11:26
User Badges:
  • Cisco Employee,

Like described in Alexander's post, by default, all VLAN's will allow to traverse a trunk port. If you want to limit/control a specific VLAN's to traverse over the trunk port, you can configure with the command:

switchport trunk allowed vlan x,y,z



Jon Marshall Mon, 08/25/2008 - 11:31
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

Just to clarify, as others have said you need to remove the "switchport access vlan 50" part of your config.

However the 2960 only supports 802.1q encapsulation so the command "switchport trunk encapsulation dot1q" is not necessary and won't be available.



This Discussion