ccna-notes3-day9
Switch interface
- Interface speed and duplex
- Speed and duplex autonegotiation
- Interface status
- Interface counters & errors
Network topology
Router interfaces have the shutdown command applied by default =will be in the administratively down/down state by default
Switch interfaces do NOT have the ‘shutdown’ command applied by default =will be in the up /up state if connected to another device OR in the down/down state if not connected to another device
command line: show interfaces status
speed ? show ⇒ choice
int f0/1 speed 100 ⇒ force 100 mbps operation
duplex ? (duplex mean can the device send and receive at the same time)
auto, full, half duplex full
checking: sh int status
a-100 ⇒ auto- 100
e..g int range f0/5-6,f0/9-12 no stut
Full duplex
Half duplex: The device cannot send and receive data at the same time. If it is receiving a frame, it must wait before sending a frame.
e.g related , Hub If device send the network at the sametime , collision happened ⇒ hub can’t work normally
Full duplex: The device can send and receive data at the same time. [t does not have to wait.
How to deal with collison? CSMA/CD
Carvier Sense Multiple Access with Collision Detection Before sending frames, devices ‘listen’ to the collision domain until t detect that other devices are not sending. If a collision does occur, the device sends a jamming signal to inform the other devices that a collision happened. Each device will wait a random period of time before sending frames again. The process repeats.
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basically it seperate the region and create a jamming signal ⇒ if happened ⇒ wait random period of time
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hubs are simple repeaters which operate at layer 1
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devices attached to a hub must in half duplex
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switch can operate in full duplex
Etherne interface ⇒ 10 Fast ether interface ⇒ 10/100 Gigabit interface ⇒ 10/100/1000
What if autonegotiation is disabled on the device connected to the switch?
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SPEED: The switch will try to sense the speed that the other device is operating at.
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If if fails to sense the speed, it will use the slowest supported speed (ie. 20 Mbps on a 10/100/1000 interface)
DUPLEX: If the speed is 10 or 100 Mbps, the switch will use half duplex. If the speed is 1000 Mbps or greater, use full duplex. ⇒ duplex mismatch = collision occur
- like 2 half duplex , 1 full duplex
- command : show interfaces
error like:
Runts: Frames that are smaller than the minimum frame size (64 bytes) Giants: Frames that are larger than the maximum frame size (1518 bytes) CRC: Frames that failed the CRC check (in the Ethernet FCS trailer) Frame: Frames that have an incorrect format (due to an ervor) Input errors: Total of various counters, such as the above four Output ervors: Frames the switch tried to send, but failed due to an ervor