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Understanding HP Networking 802.1Q Tagging

November 28, 2011

Prerequisites: CCNA level of 802.1q tagging with Cisco

HP Networking (formerly Procurve) has two networking lines. They developed their E-series (now a deprecated marketing term) in house. In April of 2010 HP bought 3com. The legacy HP equipment uses different 802.1Q tagging nomenclature from the equipment they purchased from 3Com and Cisco equipment.

There are some terminology differences between HP and Cisco which need to be clarified prior to learning about 802.1Q in the HP Networking world. When Cisco talks about a trunk, they are referring to a 802.1Q enabled link. HP Networking considers a trunk to be a port group or what Cisco calls an Etherchannel bundle. I will use the proper terms when talking about the respective vendors technologies.
When configuring Cisco VLANs, the assignment is done on the interface level. In other words, VLANs are assigned to interfaces. Legacy HP gear works the other way. Here is a comparison. In the Cisco world, VLAN assignment is done like this:

CiscoSwitch1(config)# interface FastEthernet 0/1
CiscoSwitch1(config-int)# switchport access vlan 10

HP works this way:

HPSwitch1(config)# vlan 10
HPSwitch1(config-vlan-10)# untagged 1

The next difference is brought up by the example. Notice it says untagged. HP uses tagged and untagged terminology when referring to 802.1Q port states. An untagged port is another term for Cisco’s access port. If a port is untagged on a VLAN, it means it won’t send or accept frames with a 802.1Q tag in the header. In the example, HPSwitch1 will assume all frames coming into or out of port 1 are in VLAN 10.

Tagged interfaces mean there will be 802.1Q tags involved as well as multiple VLANs. Any interface can have one untagged VLANs and multiple tagged VLANs. A frame coming into the interface without a 802.1Q tag will be considered in the untagged VLAN. If a frame comes with with a 802.1Q tag, the specified VLAN must be in the list of tagged VLANs for the interface.

An example may clear this up if it is a little confusing.

HPSwitch1(config)# vlan 10
HPSwitch1(config-vlan-10)# untagged 1
HPSwitch1(config-vlan-10)# vlan 20
HPSwitch1(config-vlan-20)# tagged 1

Port 1 is now an untagged member of VLAN 10 and a tagged member of VLAN 20.

I don’t feel one is inherently better than the other. If you find one more comfortable, go ahead and prefer that syntax. Myself, I am used to working in the Cisco world so I like that way. However, as I said, it just makes it what I’m used to, not any better.


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