Users belonging to the same VLAN on the live network may be connected to different switches, and there may be more than one VLAN across the switch. To communicate with users, interfaces between switches must be able to identify and send data frames of multiple vlans at the same time. According to the interface connection object and the processing of sent and received data frames, there are multiple interface types of vlans to adapt to different connections and networking.
Different vendors define the VLAN interface type differently. Huawei devices use three common VLAN interface types: Access, Trunk, and Hybrid.
Access interface
The Access interface is generally used to connect to user terminals (such as user hosts and servers) that do not recognize tags, or do not need to distinguish VLAN members.
In a VLAN switching network, Ethernet data frames come in the following two forms:
Untagged frame: The original frame without the 4-byte VLAN tag.
Tagged frame: A frame added to a 4-byte VLAN tag.
In most cases, an Access interface can send and receive only Untagged frames, and can add a unique VLAN Tag to only Untagged frames. The switch processes only Tagged frames. Therefore, the Access interface needs to add VLAN tags to the received frames, and the default VLAN must be configured. After the default VLAN is configured, the Access interface is added to the VLAN.
When the Access interface receives a frame with Tag and the frame contains the same VID and PVID, the Access interface can also receive and process the frame.
Before sending a frame with a Tag, the Access interface strips the Tag..
Trunk interface
Trunk interfaces are used to connect switches, routers, aps, and voice terminals that can send and receive Tagged and Untagged frames at the same time. It allows frames of multiple vlans to pass with tags, but only the frames that belong to the default VLAN are allowed to be sent from this interface without tags (that is, the tags are removed).
The default VLAN on the Trunk interface is also defined as the native VLAN by some vendors. When a Trunk interface receives an Untagged frame, it adds a Tag corresponding to the Native VLAN to the frame.
Hybrid interface
Hybrid ports can be used to connect user terminals (such as user hosts and servers) and network devices (such as hubs) that cannot recognize tags, switches, routers, and voice terminals and aps that can send and receive Tagged and Untagged frames at the same time. It allows frames with tags of multiple vlans to pass through and allows frames sent from this interface to carry tags of certain vlans (that is, frames without tags) and frames without tags of certain vlans (that is, frames without tags) as required.
Hybrid interfaces and Trunk interfaces can be used in many application scenarios, but Hybrid interfaces must be used in some application scenarios. For example, in flexible QinQ, packets from multiple vlans on the service provider's network need to strip the outer VLAN tags before entering the user's network. In this case, the Trunk interface cannot perform this function, because the Trunk interface can only allow packets from the default VLAN of the interface to pass without VLAN tags.
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