CCNA-Notes/09. Switch Interfaces.md

id, aliases, tags

id	aliases	tags
1777334914-ICRP	Switch Interfaces	CCNA Switch

Switch Interfaces

Show interface

To see all the Switch interfaces in the CLI use

SW1>en
SW1#show ip interface bief ```

[[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 stateif connected to another device
  - Or in the down/down state if not connected to another device

also you can use another command for switches

```cisco
SW1#show interface status
Port Name Status Vlan Duplex Speed Type

Port

• The physical interface on the switch Name
• Optional description configured by the admin Status
• connected notconnect ,disabled or err-disabled
  Vlan
• The VLAN the port belongs to Duplex How data flows:full, half , auto (ex: a-full) 🚀 Speed Port speed in Mbps or Gbps (ex: a-100) 🧬 Type Physical interface type (ex: 10/100BaseTX)

Configuring interface speed and duplex

For the speed

SW1#conf t
SW1(config)#interface f0/1
SW1(config)#speed ?
SW1(config)#speed 100

For the duplex

SW1(config)#duplex ?
SW1(config)#duplex full

For the description (Name)

SW1(config)#description ## to R1 ##

Configure a range of interface

You can configure a range of interface with the command

SW1(config)#interface range f0/5 - 12
SW1(config-if-range)#description ## not in use ##
//disable all the interface at once
SW1(config-if-range)#shutdown

you can do this to multiple range

SW1(config)#interface range f0/5 - 6, f0/9 - 12

Full / Half Duplex

Half duplex : The device cannot send and receive data at the same time. if it is receiving a frame, it must wait before sendig a frame.

• Devices attached to a hub must operate in half duplex

Full duplex : The device can send and receive data at the same time it does not have to wait.

• Devices attached to a switch can operate in full duplex

CSMA/CD

Carrier Sense Multiple Access with Collision Detection

• Before sendig frames, devices 'listen' to the collision domain until they 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.

Speed/Duplex Autonegotiation

• Interfaces that can run at different speeds (10/100 or 10/100/1000) have default settings of speed uto and duplex auto

• Interfaces 'advertise' their capabilities to the neighboring device, and they negociate the best spedd and duplex settings they are both capable of.

• What of autonegotiation is disabled on the device connected to the switch?

• Speed: the switch will try to sense the speed that the other device is operating at. if it fails to sense the speed, it will use the slowest supported spedd (ie. 10 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

Interface Errors

you can see errors with the command

SW1#show interfaces f0/2

Traffic Stats

5 minute input rate 1000 bits/sec, 10 packets/sec
5 minute output rate 2000 bits/sec, 20 packets/sec
     1000 packets input, 800000 bytes
     1200 packets output, 900000 byte

input rate → traffic coming into the switch port output rate → traffic leaving the port packets / bytes → total traffic count

The Error Counters

     10 input errors, 2 CRC, 3 frame, 0 overrun, 0 ignored , 0 runts, 0 giants
     5 output errors, 2 collisions, 1 late collision

Input Errors (incoming traffic issues)

• Total count of all incoming errors
• CRC (Cyclic Redundancy Check) in the Ethernet FCS trailer
• frame errors
• overrun
• Runts: Frames that are smaller than the minimum frame size (64 bytes)
• Giants: Frames that are larger than the maxium frame size (1518 bytes)
• ignored

Output Errors (outgoing traffic issues)

• Total outgoing packet errors

• collisions / Occur in half-duplex mode only late collisions / Collisions detected after first 64 bytes

  If you remember only one thing for the CCNA, remember this:
  👉 **Duplex mismatch = CRC errors + late collisions**
  It’s one of the most common exam and real-world issues.
  

The errors can be the same with a router

Review

• Interface speed and duplex
• speed and duplex autonegotiation
• Interface status
• Interface counters & error