Introduction
Port-based VLANs group VLAN members by port. A port forwards packets from a VLAN only after it is assigned to the VLAN.
Port link type
You can set the link type of a port to access, trunk, or hybrid. The port link type determines whether the port can be assigned to multiple VLANs. The link types use the following VLAN tag handling methods:
Access—An access port can forward packets only from one VLAN and send these packets untagged. An access port is typically used in the following conditions:
Connecting to a terminal device that does not support VLAN packets.
In scenarios that do not distinguish VLANs.
Trunk—A trunk port can forward packets from multiple VLANs. Except packets from the port VLAN ID (PVID), packets sent out of a trunk port are VLAN-tagged. Ports connecting network devices are typically configured as trunk ports.
Hybrid—A hybrid port can forward packets from multiple VLANs. The tagging status of the packets forwarded by a hybrid port depends on the port configuration.
PVID
The PVID identifies the default VLAN of a port. Untagged packets received on a port are considered as the packets from the port PVID.
When you set the PVID for a port, follow these restrictions and guidelines:
An access port can join only one VLAN. The VLAN to which the access port belongs is the PVID of the port.
A trunk or hybrid port supports multiple VLANs and the PVID configuration.
When you use the undo vlan command to delete the PVID of a port, either of the following events occurs depending on the port link type:
For an access port, the PVID of the port changes to VLAN 1.
For a hybrid or trunk port, the PVID setting of the port does not change.
You can use a nonexistent VLAN as the PVID for a hybrid or trunk port, but not for an access port.
As a best practice, set the same PVID for a local port and its peer.
To prevent a port from dropping untagged packets or PVID-tagged packets, assign the port to its PVID.
How ports of different link types handle frames
Actions | Access | Trunk | Hybrid | |
|---|---|---|---|---|
In the inbound direction for an untagged frame | Tags the frame with the PVID tag. |
| ||
In the inbound direction for a tagged frame |
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In the outbound direction | Removes the VLAN tag and sends the frame. |
| Sends the frame if its VLAN is permitted on the port. The tagging status of the frame depends on the port hybrid vlan command configuration. | |
In a VLAN-aware network, the default processing order for untagged packets is as follows, in descending order of priority:
MAC-based VLANs.
IP subnet-based VLANs.
Protocol-based VLANs.
Port-based VLANs.