This post only discusses how to configure an 802.1q VLAN trunk between a Cisco switch and an HP ProCurve switch. In this test I am using Cisco 3560 and HP ProCurve 2910 AL over here trunking refer to an 802.1q tagged VLAN trunk. Don’t get confused in Procurve world trunking refers to a feature like ether channel in Cisco world.
Mind that ISL trunk will not work between Cisco and HP because it is Cisco proprietary protocol. The trunk between a Cisco and HP Procurve switch must be 802.1q I rarely see ISL in use these days, and I personally consider 802.1q the preferred method of encapsulation if for no other reason than its interoperability.
Once you have configured all of the required VLANs (I hope I don’t need to explain how to configure VLANS) now configure the trunk on the Cisco switch in fa0/48 is our trunk port connected to HP ProCurve using the following commands:
Cisco3560(config)# interface fa0/48
Cisco3560(config-if)#switchport mode trunk
Cisco3560(config-if)# switchport trunk allow vlan 1,2,3
In this example I am using three VLANS Vlan 1 , 2, and 3
Here interface Fa0/48 is the trunk port on the Cisco switch.
Procurve switches, can have a VLAN either tagged or untagged on any particular port as shown in the configuration below.
Now we have enabled trunk interface between HP and Cisco for Vlan 2 only, trunk will not carry any traffic a part from Vlan 2 in order to allow Vlan 3 traffic on Trunk we need to setup port 48 in HP switch as tagged port for Vlan 3 (Clear as MUD.. !!!!)
Key point you have to setup uplink port 48 in our case on HP as tagged port for all the vlan that will pass through the trunk.
Now test connectivity between two hosts that are in the same VLAN i.e Vlan 2 , but on different switches. As you have learnt, configuration of 802.1q trunks between Cisco and HP Procurve switches is not a rocket science . if its not working double check the config and every thing should be fine.