3COM and Cisco Trunking Problem

This is really interesting topic. actually i tried to integrate 3COm 7750 with Cisco Catalyst 2960 using normal trunking port but give me a big headache. if Cisco to Cisco, we just can use

switchport mode trunk for both side.

but if 3COM to Cisco if i put

3COM
port link-type trunk
port trunk allowed vlan all

Cisco
switchport mode trunk

then your VLAN interface inside the 3COM will go down because BPDU error.

what you need to do is to define the native VLAN for both switches. of course Cisco will be VLAN 1 as a native and define in 3COM VLAN 1 as a native too. see the below configuration:

port link-type trunk => switchport mode trunk

port trunk permit vlan => switchport trunk allowed vlan

port trunk pvid vlan => switchport trunk native vlan -->this is how you define the native VLAN

3com uses 802.1Q as the standard => switchport trunk encapsulation dot1q

The hybrid port is cool, but the trunk is more recommended in this case, because it's easier to maintain and change the settings when needed than hybrid mode. The hybrid port permit that you assign more than one VLAN ID untagged on the connection, the trunk mode permit that you use just one VLAN ID untagged (PVID). The hybrid port is applicable when connecting devices that don't supports 802.1Q.

and as the result both switches can work together. good luck!