Vlan tagging

[RocketRon]

I'm pretty new to the networking game and I have a technical question. In our company we are using Aruba switches and Cisco Meraki Appliances and Wifi Access Points. In order to pass multiple Vlans through to the Appliance or the Access Points, the ports need to be configured as trunks. However, between the switches multiple vlans are easlily passed just by tagging them to the uplink ports (without trunking the port). I like the simplicity of just tagging vlans without formally trunking the ports. My question is whether this is recommendable practice or if uplinks between switches should be trunked as well. Any insights welcome!

[akg7]

Hello @RocketRon ,

Trunk port is needed if passing multiple vlans between switches.

And if connecting to host then port need to be access port.

However in Aruba/Procurve, Trunk = Tagged Port and Access= untagged port.

Thanks!

[Ivan_B · Accepted solution]

Hi @RocketRon !

I think we need to clarify several terms and then everything will become much more clear.

You are talking about two different technologies here.

1. Port Trunking. That's how it's called in ArubaOS-based switches. Other vendors call it Etherchannel, Port-channel, Link aggregation. On servers its known by 'NIC Teaming'. It is the feature that allows you to "bundle" several physical L2 (sometimes L3 too) links and make this bundle working as a single logical Ethernet interface. You make it for increased throughput, redundancy etc. Such link aggregations may be static or may use protocol like LACP that assist switches on both side of such aggregation to negotiate port trunk's parameters and avoid manual configuration mistakes (which are possible with static trunks) that can lead to traffic blackholing or even L2 loops.

2. VLAN trunking. VLAN trunk is an Ethernet interface (can be link aggregation too, btw!) that can pass traffic from multiple VLANs over a single Ethernet interface. It does it by multiplexing frames from several VLANs. In order to distinguish frames from different VLANs when a frame is sent out of VLAN trunk it gets 'marked' or 'tagged' - a special identifier is being added to the frame's header representing VLAN number. That's how receiving side knows that this frame belongs to VLAN 10, for example and that frame to VLAN 20 etc...

Both terms have word 'trunk', that's why no surprise people often confuse them. Just FYI, inside one vendor there is no confusion:

HPE (ArubaOS): Port trunking ; tagged VLAN on a port
HPE (Comware): Link aggregation ; VLAN trunk
Cisco: Etherchannel ; VLAN trunk
Meraki - I guess it's like in Cisco, since they are Cisco's subsidiary since long time.

[RocketRon]

Thank you for this very insightful explanation!