Shulou(Shulou.com)06/02 Report--

First, the data link layer

Data link layer-establishing logical connection, hardware address addressing, error checking and other functions, data communication through MAC address, frame packaging, frame transmission, frame synchronization. The switch operates at the data link layer.

1. Ethernet works at the data link layer

2Query CSMACompCD-Carrier sense multiple access with collision detection

Ethernet uses CSMA/CD to avoid signal collision

Principle: similar to traffic lights

3, Ethernet MAC address

An Ethernet address is used to identify a single device or group of devices on an Ethernet.

The length of the MAC address is 48 bits (6 bytes). The first 24 bits represent the manufacturer and the last 24 bits represent the network card number.

A 0 bit of a MAC address indicates that the MAC address is a unicast address, and a value of 1 indicates a multicast address. All 48 bits are 1 to indicate the broadcast address.

Ipconfig / all View MAC address

Note: the address of a physical network card must be a unicast address, that is, bit 8 must be 0

4, the frame format of Ethernet

The length of Ethernet frame data is 46-1500

The length of Ethernet frame is 64-1518

Frame check sequence (FCS): the checksum from the beginning of the destination address to the end of the data.

Type / length: used to identify the type of upper layer protocol or the byte length of subsequent data.

5. The data link layer is divided into two sublayers:

1) MAC media access control:

Encapsulate the data handed over by the upper layer into a frame for transmission

Implement and maintain media access control protocols

Bit error detection

Addressing of MAC Fram

2) LLC logical link control:

Establish and release logical connections at the data link layer

Provide an interface with the upper layer

Number the frame

6. Ethernet naming method

N-signal-physical medium

N: data rates in megabits, such as 10,100,100, 1000

Signal: Base indicates baseband transmission

Physical media: identifies the type of media (TX 2 versus five types of UTP)

II. Ethernet switch

1. The switch is the main equipment used to connect the local area network. The switch divides the collision domain and realizes full-duplex communication.

2. The working principle of the switch

Initial state

Learn according to the source MAC address

The port except the source port broadcasts unknown data frames

Receiver responds

The switch implements unicast communication (forwarding)

Update: aging time 300 seconds

When the MAC address of the corresponding port of the switch changes

3. Switch Ethernet interface duplex mode

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: data can be transmitted bidirectionally and simultaneously between two data stations

4. Conflict and broadcast domain

A broadcast domain is a collection of nodes that receive the same broadcast message.

The switch divides the collision domain, but not the broadcast domain, that is, all ports on the switch belong to the same broadcast domain

5. Internal switching mode of the switch

Store and forward

Fast forwarding

Sectional filtration

3.

View the MAC address tabl

Display mac-address

View switch MAC addr

Display bridge mac-address

View neighbor device information

[Huawei] lldp enable

Display lldp neighbor brief

Configure duplex mode and port rate in non-self-negotiating mode

[HUAWEI-GigabitEthernet0/0/1] undo negotiation auto

[HUAWEI-GigabitEthernet0/0/1] duplex {half | full}

[HUAWEI-GigabitEthernet0/0/1] speed {10 | 1000 | 2500}

Configuration Management IP

[Huawei] interface vlan 1

[Huawei-Vlanif1] ip address 192.168.1.254 255.255.255.0

[Huawei-Vlanif1] undo shutdown

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