Data Link Layer Basics - Switches
1. Ethernet / working principle
Ethernet adopts CSMA/CD - carrier sense multiple access with conflict detection - avoid signal conflict
Working principle: monitor whether the channel is idle before sending, if it is idle, send directly, if there is a conflict, stop Send, wait for a period of time to continue sending
2. Ethernet MAC address - is used to identify a single device or a group of devices on the Ethernet. The first 8 digits are the manufacturer number provided by IEEE (Institute of Electronics and Electrical Engineering), the last 24 digits are the device number
3. Ethernet frame format
destination address source address type data frame validation sequence
6 bytes 6 bytes 2 bytes 46-1500 bytes 4 bytes
4. Data link layer sublayer :
Logical Link Control Layer (LLC): Provides an interface with the upper layer, adds a sequence number to the frame, establishes and releases the logical connection of the data link layer
Media Access Control Layer (MAC) : Error detection MAC addressing realizes and maintains the control protocol of medium access and accepts upper layer data encapsulation into frames for transmission.
5. The working principle of the switch - learning, broadcasting, forwarding, and updating.
The switch divides the collision domain to achieve full-duplex communication. However, the broadcast domain cannot be divided
. 6. Internal switching mode of the switch:
store and forward - the most widely used error detection speed is slow
Fast forwarding - fast speed, can not debug the
segmentation filter - check whether the length of the data packet is 64 bytes
less than 64 The description is that if the fake packet is greater than 64, it will be sent without verification.
Switch simple commands:
1. Check the usage help
<Huawei> ? Query all commands in the current mode
2. Check the copy command help
<Huawei> copy ?
3. Display Chinese help
<Huawei> language-mode Chinese Chinese help
4. Query the MAC address table
[Huawei] display mac-address Query the MAC address table
5. View the switch address
[Huawei] display birdge mac-address View the switch address
6. View Neighbor device information
LLDP protocol - used to query neighbor device information
[Huawei] LLDP enable Enable DDLP protocol
[Huawei] display lldp neighbor brief Query neighbor device information
7. Configure switch speed/duplex mode
Note (port-based configuration): Manual To configure the rate and duplex mode, you need to disable the auto-negotiation function
[Huawei] Interface Ethernet 0/0/1
[Huawei-GigabitEthernet0/0/1] Undo negotiation auto Disable auto-negotiation
[Huawei-GigabitEthernet0/0/1] Duplex half/ full configuration Full-duplex, half-duplex
[Huawei-GigabitEthernet0/0/1] Speed 10/100 Configure the port speed