————Data link layer analysis, basic switch configuration————
[Analysis of Data Link Layer]
<<Introduction to Data Link Layer>>
<Function>
Establishment, maintenance and teardown of data link, frame packaging, transmission and synchronization, frame error recovery, flow control
<Ethernet>
Concept: usual LAN used, at the data link layer
Ethernet MAC address
Used to identify a single device or group of devices on an Ethernet
<Ethernet name>
100 BASE-TX
100 Data rate 100M
BASE Baseband, i.e. the physical medium is dedicated to Ethernet
TX UTP or STP twisted pair connection
<MAC address>
|<--------24bit vendor ID------->|<--------24bit unique number- ------->|
48 bit = 6 Byte
Bit 8: 0-physical address (unicast), 1-logical address (multicast)
<Ethernet frame format>
--802.3 Ethernet frame format
preamble Frame Start Delimiter Destination Address Original Address Type/Length Data Frame Check Sequence
7 Byte 1 Byte 6 Byte 6 Byte 2 Byte 46~1500 Byte 4 Byte
---------------- ----------------Data link layer encapsulation ----------------------------
------------------------------------------------Physical Layer Package -------------------------------------------------
<Two sublayers of the data link layer>
Media Access Control (MAC) sublayer
Encapsulates the data handed over from the upper layer into frames for transmission (on the contrary, disassembles the frames when receiving)
Bit error checking
Addressing of MAC frames: source station, Destination station
Relevant protocol: CSMA/CD
Logical Link Control (LLC) sublayer
Establish and release the logical connection of the data link layer
Provide the interface with the upper layer
Add sequence number to the frame
<< Ethernet switch >>
< switch concept> The
switch is The main equipment used to connect the local area network The switch can forward data intelligently according to the destination address
in the Ethernet frame. <The role of the switch
>
Divide the collision domain to realize full-duplex communication . MAC address table broadcast If the destination address is not in the MAC address table, the switch broadcasts the data frame to all other ports. Forwarding The switch forwards the data frame according to the MAC address table. Update the switch if it finds the ingress port of a frame and the source MAC address in the MAC address table If the port where the address is located is different, the MAC address table will be re-learned to the new port, and the aging time of the MAC table is 300 seconds . the half duplex
There is only one channel, and at the same time, only one-way transmission is possible. Full-
duplex
dual-channel, and two-way data transmission is possible at the same time.
<Switch Internal Switching Mode>
Store and Forward
Fast Forwarding
Segment Filtering
[Basic switch configuration]
<<Switch view>>
View MAC address table
Switch# show mac-address-table
CDP protocol, view neighbor Cisco device information
Switch# show cdp neighbors (detail)
<<Switch interface and address configuration>>
<Interface Working mode configuration>
Enter interface mode
Switch(config)# int f 0/1
Switch(config-if)
#Specify the duplex mode of the interface
Switch(config-if)# duplex {full|half|auto}
Specify the communication rate of the interface
Switch(config-if)# speed {10|100|1000|auto}
View the duplex mode and communication rate of the Ethernet interface
Switch# show int f 0/24