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Irfan Ullah | Cisco CCNA | Module 3 - Layer 2 Data Link

By: Irfan Ullah | Related Course: Cisco CCNA | Published: June 20, 2016 | Modified: June 26, 2016
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NotepadBroadcast and collision domain

by default all cisco switches are one broad cast

but router breaks the broadcast domain

collision domains

six collision domains


Burnt In Address = burnt in it on laser these addresses MAC

NotepadData Link Layer

controls communication between one device and the next immediate device to it

comm on the immediate physical link 

PDU=Protocol Data Unit

Addressing Scheme

source address and destination address

MAC (medium access control)= six byte or 48 bits and in HEX

HEX= 1-9 and A-F

First 24 bites of MAC are OUI Field or government defined and vendor specific.

the 7th most significant bit is called in MAC address is called UL bit.

if that bit is Off the this mac address is universally unique and if this bit is On it means this address assigned locally.



NotepadLab 2


Router>= User Mode and have a limited capability

Router#= Privilege Mode 

Notepadlayer 2

Frame Check Sequence FCS

Cyclic Redundancy Check=CRC

broadcast and unicast difference

device work at data link layer is switch.

operation of switch


virtual local area network

VLAN 1 to VLAN 1005 are normal

VLAN COnfiguration

switch#VLAN database

switch(Vlan)#vlan 50 name test


switvh# show vlan brief

This is the new way


Switch(config-vlan)#name ccna

Switch(config-vlan#do sh vlan brief

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