Specifications

CHAPTER 2
VLAN Implementation
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Protected: false
Unknown unicast blocked: false
Unknown multicast blocked: false
Broadcast Suppression Level: 100
Multicast Suppression Level: 100
Unicast Suppression Level: 100
VLAN Trunking
A trunk is a link that carries traffic for more than one VLAN. Trunks multiplex traffic from multiple VLANs. They
typically connect switches and enable ports on multiple switches to be assigned to the same VLAN.
Two methods of identifying VLANs over trunk links are:
n Inter-Switch Link (ISL): A Cisco proprietary method that encapsulates the original frame in a header, which
contains VLAN information. It is protocol-independent and can identify Cisco Discovery Protocol (CDP) and bridge
protocol data unit (BPDU) frames.
n 802.1Q: Standards-based, tags the frames (inserts a field into the original frame immediately after the source MAC
address field), and supports Ethernet and Token Ring networks.
When a frame comes into a switch port, the frame is tagged internally within the switch with the VLAN number of the
port. When it reaches the outgoing port, the internal tag is removed. If the exit port is a trunk port, its VLAN is identified
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CCNP SWITCH 642-813 Quick Reference by Denise Donohue