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

What is a switch?

The switch is the main equipment used to connect the local area network.

The interactive machine can intelligently forward data from the target address in the Ethernet frame, and the switch works at the data link layer.

Switch divides collision domain to realize duplex communication

How the switch works

Learning: form a mac address table by learning the source mac address of a data frame

Broadcast: if the destination address is not in the mac address table, the switch reports to the

All ports other than the source port of the data frame broadcast the data frame

Forwarding: the switch broadcasts and forwards data frames according to the mac address form

Update

The aging time of switch mac address table is 300 seconds.

If a frame, such as a port, is found to be different from the port of the source mac address in the mac address table, the switch relearns the mac address to the new port

Conflict domain and broadcast domain

Internal switching mode of the switch:

Store-and-forward-the most widely used, slow error detection

Fast forwarding-high speed, can not troubleshoot

Segmentation filtering-check whether the packet length is 64 bytes

If it is less than 64, it means that if the fake packet is greater than 64, the data check will not be provided.

Ethernet / how it works

Ethernet uses CSMA/CD-- carrier sensing multiple access with collision detection to avoid signal collisions

How it works: listen to whether the channel is idle before sending, if it is idle, send it directly, stop sending if there is a conflict, and wait for a period of time to continue sending.

Ethernet MAC address-is used to identify a single device or group of devices on Ethernet. The first 8 digits are the manufacturer number, provided by IEEE (Electronic and Electrical Engineering Association), and the last 24 is the equipment number.

Ethernet frame format

Destination address source address type data frame validation sequence

6 bytes 6 bytes 2 bytes 46-1500 bytes 4 bytes

Data link layer sublayer:

Logical Link Control layer (LLC): provides an excuse to the upper layer, adds a sequence number to the frame, and establishes and releases logical connections at the data link layer

Media access Control layer (MAC): error detection MAC addressing implementation and maintenance of media access control protocols accept upper layer data encapsulated into frames for transmission.

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