<Jeremy's IT Lab> Day9: Switch Interfaces

Switch Interfaces

 

 

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

 

SW1#show interfaces status

##Port, Name(=descriptions), Status(conn/notconn), Vlan, Duplex(a-full, auto), Speed(a-100), Type

 

#interface range f0/5 - 6, f0/9 - 12 (f0/5, f0/6, f0/9, f0/10, f0/11, f0/12)

##change multiple devices at once

 

Half duplex: cannot send/receive data at the same time

-> devices attached to a hub must poerate in half duplex

Full duplex: can send/receive data at the same time (mordern nw)

-> devices attached to a switch can operate in full duplex

 

Old(Hub) repeater: collision occur

CSMA/CD(Carrier Sense Multiple Access with Collision Dectection)

-> before sending frames, device 'listen' to collision.

-> if collision does occur, device send jamming signal to inform the other devices that collision happend

-> Each device will wait a random perod of time before sending

 

Speed and duplex autonegotiation:

-> Interfaces can run at different speeds(10/100 or 10/100/1000) have default setting of speed auto and duplex auto

-> Interfaces 'advertise' their capabilities to neighboring device, and they negotiate best speed and duplex settings

E = 10

F = 10 or 100

G = 10 or 100 or 1000

* Without Autonegotiation cannot sense duplex.

-> Duplex mismatch = collsions will occur(poor nw performance)

 

SW#show interfaces f0/2

## show various counters of errors individual

Runts: Frames that are smaller than the minimum frame size(64 bytes)

Giants: Frames that are smaller than the minimum frame size(1518 bytes)

CRC: Frames that failed the CRE check (in the Ethernet FCS trailer)

Frame: Frames that have an incorrect format (du to an error)

Input errors: Total of various counters, such as the above four

Output errors: Frames the switch tried to send, but tailed due to an error

---

Acronym

• CSMA/CD : Carrier Sense Multiple Access with Collision Dectection