Switch two-tier interface access, Trunk, hybird three modes of processing of VLANs

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Switch two-tier interface access, Trunk, hybird three modes of processing of VLANsnetwork workers old Zhang net work 1 weeks ago

VLAN technology is a modern computer network in a classic technology, whether it is the traditional network in the metropolitan Area Network and data center, or the current Hot SDN, can see the figure of the VLAN. However, many Meng new network workers on the Switch VLAN tag processing problem is like mirrors, this article to explore, to share with you the switch for VLAN tag processing process.

The two-tier port of the normal switch has three common port types: Access, trunk, hybird,access ports are generally used as PC or server host access, packets through the port are not VLAN tag, trunk port can allow packets of multiple VLANs, General connection to other switches; The Hybird port is flexible, can be based on the user needs, the packet through the Port VLAN tag marking and labeling action, you can connect the host can also connect other switches; Before you begin, remember that all data packets inside the switch have VLAN tags, Below we analyze the switch port in two directions to the VLAN tag processing process to detail the difference between the three port types;

Access port:

packets that pass through the access port are not VLAN-tagged and belong to only one VLAN;

In the access port in the direction, after the switch received the packet, the first to determine whether the VLAN tag, there is dropped packets, not the port has been configured VLAN tag;

On the access port out of direction, the switch will hit a packet with the same VLAN tag as the port forward, and remove the VLAN tag into the normal packet.

Trunk Port:

packets through the trunk port must be tagged with vlan;

In the trunk port in the direction, after the switch received the packet, the first to determine whether the VLAN tag, no drop packets, and then the corresponding VLAN to be forwarded;

In the trunk port direction, the switch forwards the packet with VLAN tag intact, without VLAN tag packets will not be forwarded from the trunk port.

There is a special case on the trunk port, if the native VLAN (also called Pvid) is configured, the forwarding method is equivalent to the access port, and when the incoming message from the port does not carry the VLAN tag, the native VLAN tag is called, and when the packet is sent out from the port native When the VLAN tag is removed, the tag is stripped.

Hybird Port:

As the name implies, this is a hybrid port, which is a mixture of access and trunk two ports, which can either forward a VLAN-free tag message or a VLAN tag message, and the tag VLAN and UNTAG VLAN are usually configured on the Hybird port. For the tag VLAN, it is forwarded in the same way as the trunk port, and it is forwarded in the same way as the access port for UNTAG VLAN;

In the Hybird port in the direction, after the switch received the packet, the first to determine whether the VLAN tag, not discarded, if there is no VLAN tag but configured Pvid, then the Pvid VLAN tag, there is the corresponding VLAN forwarding, in the direction of not looking at UNTAG configuration;

In the Hybird port direction, for the packet configured with the tag VLAN, sent out intact, for the port configuration of the Untag VLAN packet, the VLAN tag is removed and sent out, if it is Pvid VLAN, then the VLAN tag is removed and sent out;

We might as well do three small experiments in the text, after the mastery of the VLAN tag no doubt.

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Switch two-tier interface access, Trunk, hybird three modes of processing of VLANs