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

A switch is a network device for forwarding electrical (optical) signals. It can provide an exclusive electrical signal path for any two network nodes of the access switch. The most common switch is the Ethernet switch. The switch operates at the second layer of the OSI reference model, the data link layer.

Functions of the data link layer

Establishment, maintenance and dismantling of data links

Frame wrapper, frame transmission, frame synchronization

Error recovery of frame

Flow control

Switch principle Ethernet MAC address

Used to identify a single device or group of devices on an Ethernet that consists of 48 bits of binary.

Ethernet frame format

Ethernet has a variety of frame formats, commonly used is the Ethernet II format

Principle of switch forwarding

(1) initial state

A new switch has just connected to the network and knows nothing about the outside world.

(2) MAC address learning

An and B communicate. When the data frame arrives at the switch, the switch MAC address table learns the source MAC and port number.

(3) broadcast unknown data frames

After the switch does not know where B is, it will generate a broadcast, looking for B.

(4) response from the recipient

B responds to An after receiving. At this time, B becomes the source host. After arriving at the switch, the switch MAC address table learns the source MAC and port number and forwards it to A.

(5) the switch realizes unicast communication.

After the switch MAC address table learns the MAC address and port of both sides, the two computers can communicate with each other and the switch can forward it directly to realize unicast communication.

The operating mode of the Ethernet interface of the switch

Simplex: data can only be transmitted in a single direction between two data stations

Half-duplex: two-way data transmission between two data stations, but not at the same time

Full-duplex: two-way and simultaneous transmission between two data stations

Switch Ethernet interface rate

Negotiate when the interface is connected

If the negotiation fails, it will not be able to communicate properly.

The hierarchical relationship of the simple configuration command line of the switch

A simple command from time to time

? Show commands, display parameters, list of commands

Tab complement command, prompt command

Enable user mode enters privileged mode

Disable privileged mode returns to user mode

Configure terminal privileged mode enters global mode

Interface fastethernet1/0 global mode enters interface mode ("1apper0" is the corresponding interface to be set)

Exit returns to the upper level

End returns privileged mode

No ip routing turns off the routing function

Show running View running configuration

Do show running View running configuration across modes

Show version view version information

Show mac-address-table View MAC address tabl

Speed 100sets the rate to 100M/s

Duplex full sets the interface mode to full-duplex

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