Trunking Header Tells Switch2 What to Do

Trunking Header Tells Switch2 What to Do

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Now, switch2 knows how to process each received frame. When it receives frames in port FastEthernet 24, it expects to see a trunking header, which identifies the VLAN. That tells switch2 which address table to use.

When switch2 needs to send frames out port Fa24 to switch1, switch2 also adds a VLAN trunking header, knowing that switch1 expects to be able to find the header to identify the right VLAN.

So, now to the other use of the term trunk, along with some related terms. The term VLAN trunk, or sometimes simply trunk, refers to a link between two switches over which the additional trunking header is added, as in Figure 7-9. The term VLAN trunking, or simply trunking, refers to the process of adding (when sending) and removing (upon receipt) the extra headers that identify the VLANs.