Trunk port VS Aggregated Link

[Spiker]

Just a quick question

I have read many of the pdfs for ESX 3 including some networking specific papers. However can someone give me a simple explanation of the difference between a trunk port and an aggregated link in VLAN's ?

Thanks

[MR-T]

My understanding is the "trunk" port simply presents multiple VLANs down the one or "bonded" cables.

The link aggregation refers to combining more than one connection into a team.

With a trunk port, you'd configure which VLANs are allowed down the particular port at the physical switch level. You'd then configure the port groups on the virtual switches to use these VLAN numbers.

[Spiker]

Thanks Mr T

So an aggregated link is simply 2 or more links from the same source to the same destination - such as 2 ethernet cables connecting 2 switches together - which have been configured as 'aggregated links' ? - for the purpose of redundancy ?

I take it then a trunk port could be aggregated too ? - with another trunk port ?

Is an aggregated link generally also a trunk port anyway ? so that 1 trunk port is set up to forward vlan traffic between switches - and by adding another trunk port between the same switches could those 2 trunks be optionally aggregated to create an aggregated trunk ?

So a trunk port is just a connection into a switch accepting vlan/non vlan traffic ? and by having more than one for redundancy this is then known as aggregated ?

Sorry not trying to confuse - just trying to understand

[Paul_Lalonde]

The confusion surrounding "trunk" and "aggregate link" (or "team", "bond", etc.) stems from the fact that different networking vendors have chosen two different ways to say the same thing.

In original "Cisco speak", a trunk is simply a physical connection that provides VLAN tagging. In other words, an Ethernet link that provides the ability for multiple VLANs to transit it.

Other vendors, ie. HP, have chosen to call this a "tagged port." Tagged in that it allows a physical link to carry traffic from multiple VLANs.. with each VLAN being "tagged" with its own ID.

Both do exactly the same thing.

In the Cisco world, an aggregation of physical links into a logical bond is called an Etherchannel. It's also known as 802.3ad, LACP, etc. depending on the actual configuration.

However, HP (and others) confuse the issue by calling an aggregate link a "trunk". In non-Cisco environments, a trunk is an aggregation of physical links into a bond.

So, to Cisco, a trunk is a multi-VLAN link and an Etherchannel is a multi-physical-link aggregation.

For non-Cisco, a trunk is a multi-physical-link aggregation and a tagged port is a multi-VLAN link.

Make sense?

Paul

[oreeh]

Nice explanation

To add some more confusion - a tagged port could be a single-VLAN link too and a trunk between switches could be a mesh instead.

[Spiker]

Thanks guys - particularly Paul for your explanation

You have really helped - cheers !

[oreeh]

then give him 10 points