Layer One - Physical

Cables

Repeaters

Hubs repeats the signal to all other ports except the port that originated the signal

Base - Baseband - one at a time Broadband - More than one signal at a time

Layer Two - Data Link

- controls data on the immediate physical link between devices

MAC Media Access Control 48 bits hexidecimal

OUI Field 24 bits is vendor specific

7th most significant bit - UL - if turned off (0) - the address should be universally unique – The 7th bit turned on (1) - the address has been assigned locally

Protocal unit called a frame FCS - Frame Check Sequence aka CRC - cyclic redundancy check

Switches work here

Switches learn MAC addresses by looking at the source address field in the frame Switches make their forwarding decisions based on the destination MAC address in the frame Once the MAC tabe

Flood is not the same as a broadcast, flood is done when broadcast has all FF in the destination MAC address in the frame broadcast is a one to all transmission sent on purpose unicast is a one to one sent message

Cisco packet tracer CLI → show mac address-table

DYNAMIC → switch learned port

bia - burned in address

Layer 2 - Broadcast Domains

switch = transparent bridging

Broadcast - all switches are one broadcast domain by default Broadcast - can not transverse a router

Collision domains -

Encapsulation = layer header + data

4- Transport Layer chunk of data = Segment -

3- Network Layer - chunk of data - packet

2- Data Link Layer - chunk of data - frame - Ethernet - MAC address

1- Physical Layer

Data Networks and Addressing

Addressing at the Data Link Layer - frame

media access control - 48 bit hexadecimal number local address MAC -

1st 24 bits = manufacturer ID

2ne 24 bits = serial number

Packet Internet or Inter-Network Groper (PING) used to test the reachability of a host on an Internet Protocol (IP) network.

Cisco Certifications

Entry Level - CCENT - Entry Network Technician
Associate - CCNA - Network Associate - most common - Route/Switch
Professional - CCNP - Network Professional
Expert - CCIE - Internetworking Expert

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