aadd day 9 Switch Interfaces
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shango-wk
176
09. Switch Interfaces.md
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176
09. Switch Interfaces.md
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id: 1777334914-ICRP
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aliases:
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- Switch Interfaces
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tags: []
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---
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# Switch Interfaces
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## Show interface
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To see all the [[Switch]] interfaces in the CLI use
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```cisco
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SW1>en
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SW1#show ip interface bief
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```
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[[Router]] interfaces have the shutdown command applied by default
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- will be in the administratively down/down state by default
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Switch interfaces do Not have the shutdown command applied by default
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- will be in the up/up stateif connected to another device
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- Or in the down/down state if not connected to another device
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also you can use another command for switches
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```cisco
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SW1#show interface status
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Port Name Status Vlan Duplex Speed Type
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```
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Port
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- The physical interface on the switch
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Name
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- Optional description configured by the admin
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Status
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- connected notconnect ,disabled or err-disabled
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Vlan
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- The VLAN the port belongs to
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Duplex
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How data flows:full, half , auto (ex: a-full)
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🚀 Speed
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Port speed in Mbps or Gbps (ex: a-100)
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🧬 Type
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Physical interface type (ex: 10/100BaseTX)
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## Configuring interface speed and duplex
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For the speed
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```cisco
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SW1#conf t
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SW1(config)#interface f0/1
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SW1(config)#speed ?
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SW1(config)#speed 100
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```
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For the duplex
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```cisco
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SW1(config)#duplex ?
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SW1(config)#duplex full
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```
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For the description (Name)
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```cisco
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SW1(config)#description ## to R1 ##
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```
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## Configure a range of interface
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You can configure a range of interface with the command
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```cisco
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SW1(config)#interface range f0/5 - 12
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SW1(config-if-range)#description ## not in use ##
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//disable all the interface at once
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SW1(config-if-range)#shutdown
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```
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you can do this to multiple range
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```cisco
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SW1(config)#interface range f0/5 - 6, f0/9 - 12
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```
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## Full / Half Duplex
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**Half duplex** : The device cannot send and receive data at the same time.
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if it is receiving a frame, it must wait before sendig a frame.
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- Devices attached to a hub must operate in half duplex
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**Full duplex** : The device can send and receive data at the same time
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it does not have to wait.
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- Devices attached to a switch can operate in full duplex
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### CSMA/CD
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Carrier Sense Multiple Access with Collision Detection
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- Before sendig frames, devices 'listen' to the collision domain until they detect that
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other devices are not sending
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- if a collision does occur, the device sends a jamming signal to inform the other
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devices that a collision happened
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- Each device will wait a random period of time before sending frames again.
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- The process repeats.
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## Speed/Duplex Autonegotiation
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- Interfaces that can run at different speeds (10/100 or 10/100/1000) have default settings
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of speed uto and duplex auto
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- Interfaces 'advertise' their capabilities to the neighboring device, and they negociate
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the best spedd and duplex settings they are both capable of.
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- What of 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 it fails to sense the speed, it will use the slowest supported spedd
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(ie. 10 Mbps on a 10/100/1000 interface)
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- **Duplex**: if the speed is 10 or 100 Mbps, the switch will use half duplex.
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if the speed is 1000 Mbps or greater, use full duplex
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## Interface Errors
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you can see errors with the command
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```cisco
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SW1#show interfaces f0/2
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```
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### Traffic Stats
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```cisco
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5 minute input rate 1000 bits/sec, 10 packets/sec
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5 minute output rate 2000 bits/sec, 20 packets/sec
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1000 packets input, 800000 bytes
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1200 packets output, 900000 byte
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```
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input rate → traffic coming into the switch port
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output rate → traffic leaving the port
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packets / bytes → total traffic count
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### The Error Counters
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```cisco
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10 input errors, 2 CRC, 3 frame, 0 overrun, 0 ignored , 0 runts, 0 giants
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5 output errors, 2 collisions, 1 late collision
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```
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#### Input Errors (incoming traffic issues)
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- Total count of all incoming errors
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- CRC (Cyclic Redundancy Check) in the Ethernet [[FCS trailer]]
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- frame errors
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- overrun
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- Runts: Frames that are smaller than the minimum frame size (64 bytes)
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- Giants: Frames that are larger than the maxium frame size (1518 bytes)
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- ignored
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#### Output Errors (outgoing traffic issues)
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- Total outgoing packet errors
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- collisions / Occur in half-duplex mode only
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late collisions / Collisions detected after first 64 bytes
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If you remember only one thing for the CCNA, remember this:
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👉 **Duplex mismatch = CRC errors + late collisions**
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It’s one of the most common exam and real-world issues.
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**The errors can be the same with a router**
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## Review
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- Interface speed and duplex
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- speed and duplex autonegotiation
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- Interface status
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- Interface counters & error
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