Information on VLAN Trunking

Cisco Trunking

• VLANs are local to each switch's database, and VLAN information is not passed between switches.
• Trunk links provide VLAN identification for frames traveling between switches.
• Certain types of switches can negotiate trunk links.
• Trunks carry traffic from all VLANs to and from the switch by default but can be configured to carry only specified VLAN traffic.
• Trunk links must be configured to allow trunking on each end of the link.

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By default, a trunk port sends traffic to and receives traffic from all VLANs. All VLAN IDs are allowedon each trunk. However, you can remove VLANs from this inclusive list to prevent traffic from the

specified VLANs from passing over the trunk. You can add any specific VLANs later that you may wantthe trunk to carry traffic for back to the list.

show interface trunk