Shulou(Shulou.com)06/01 Report--

VLAN (Virtual Local Area Network) is a virtual local area network

Role of VLAN

Reduce the number of broadcast messages (isolated broadcast)

is safe

high maintainability

VLAN partition method

Based on port division (current mainstream)

MAC address based partitioning

policy-based

Port roles for partitioning VLANs

Trunk: Port can allow multiple VLANs to pass through, can receive and send multiple VLAN messages, generally used for ports connected between switches;

Hybrid: The type of port can allow multiple VLANs to pass through, can receive and send messages from multiple VLANs, can be used for connections between switches, and can also be used to connect users 'computers.

Access: A port can only belong to one VLAN, and is generally used to connect to a computer's port.

Note: Hybrid ports allow multiple VLAN packets to be sent without tagging, while Trunk ports only allow default VLAN packets to be sent without tagging.

VLAN Message Format

2: Type of byte

3bit Priority

1bit: Mark type (distinguish network frames)

12bit VLAN ID （1-4096）

The process by which a switch accepts and forwards information

Acess port receiving message: When receiving a message, determine whether there is VLAN information: if there is no PVID of the port, and exchange forwarding, if there is, directly discard (default).

Acess port sending message: stripping VLAN information of the message and sending it directly.

trunk port receiving message: receiving a message, judging whether there is VLAN information: if there is no PVID of the port, and switching forwarding; if there is, judging whether the trunk port allows the VLAN data to enter: if yes, forwarding, otherwise discarding

trunk port sending message: Compare PVID of port and VLAN information of message to be sent, strip VLAN information if they are equal, and send again; if not, send directly

hybrid port receives message: receives a message, judges whether there is VLAN information: if there is no VLAN information, then marks the PVID of the port, and performs exchange and forwarding; if there is VLAN information, judges whether the hybrid port allows the VLAN data to enter: if yes, then forward, otherwise discard (at this time, the untag configuration on the port is not considered, and the untag configuration only works when sending messages)

hybrid port sending message:

1. Determine the attributes of the VLAN on this port (disp interface can see which VLANs are untag and tag for this port)

2. If it is untag, strip the VLAN information and send it again. If it is tag, send it directly.

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