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Switch

switch

Overview

The link type of VLAN can be divided into access link and trunk link.

  • Access link is part of only one VLAN, and normally is for end devices.
  • Any device attached to an access link is unaware of a VLAN membership.
  • An access-link connection can understand only standard Ethernet frames.
  • Switches remove any VLAN information from the frame before it is sent to an access-link device.
  • Trunk link can carry multiple VLAN traffic and normally is used to connect switches to other switches or to routers.

Access Port

l Belong to one VLAN.

l Commonly used to connect computer ports.


  • Strip the VLAN information in the packet and forward the packet directly.

Trunk Port

l Allow multiple VLANs through.

l Receive and send multiple VLAN packets.

l Typically used for connection between switches.


  1. Compare the PVID of the port and the VLAN information in the packet to be transmitted.

  2. If they are the same, proceed to Step 3, otherwise, proceed to Step 4

  3. Strip the VLAN information in the packet and forward the packet.

  4. Forward the packet directly.

Hybrid Port

l Allow multiple VLANs through.

l Receive and send multiple VLAN packets.

l Used for connection between switches, or switch and computer.


  1. Check the VLAN attributes on this port by running the command disp interface to se whether the VLAN attributes is “tagged” or “untagged”

  2. If I is untagged, proceed to Step 3, if it is tagged, proceed to step 4.

  3. Strip the VLAN information in the packet and forward the packet.

  4. Forward the packet directly.

Summary

Port Type Support Mode Common use cases Comment
Access single untagged VLAN PC/Printer to switch
Trunk single untagged VLAN & multiple tagged VLANs switch/hypervisor to switch VLAN 1 can be Tagged (Untagged by default)
Hybrid Support Untagged VLANs & Tagged VLANs 1. Physical Connection: IP Phone to Network Switch Port & a PC to IP Phone’s Switch port; 2. Logical Connection: Voice VLAN as Tagged & Data VLAN as Untagged & Switch port in Trunk mode 1. Usually the Untagged VLAN number = Native/Default VLAN number; 2. Support for multi-Untagged Frames, usually require the use of protocol-based VLANs; 3. VLAN 1 can be Tagged (Untagged by default)

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