CCNA-1 V5.0 Ch 5 - Ethernet - 3

The ARP table is maintained dynamically. There are two ways that a device can gather MAC addresses

1-One way is to monitor the traffic that occurs on the local network segment., 2-Another way a device can get an address pair is to send an ARP request

ARP protocol provides two basic functions

1-Resolving IPv4 addresses to MAC addresses, 2-Maintaining a table of mappings

802.3 Ethernet Frame - Fields?

1-Source Physical address; 2-Frame check sequence, 3- Destination Physical address

major types of Layer 3 interfaces are:

1-Switch Virtual Interface (SVI), 2-Routed Port -, 3-Layer 3 EtherChannel

Benefits of adjacency Table:

1-be built separately from the FIB table, allowing both to be built without any packets being process switched., 2-not stored in cache entries, so changes in a MAC header rewrite string do not require invalidation of cache entries.

two issues with ARP:

1-broadcasts and 2-security

MAC - ethernet MAC sublayer has 3 responsibilities:

1-data encapsulation, 2-Media access control

Unicast Frame

1-destination MAC, 2- Source MAC, 3-Source IP, 4-Dest IP, 5-User data, 6-Trailer

Reasons for subnetting a network include

1-manage broadcast traffic; 2- similiar network requirements, 3- security

Switch Frame Forwarding Method

the destination NIC discards any incompelte frames using thsi frame forwarding method

Ethernet MAC address used to ransport

the fame across the local media

an ethernet MAC address is used to transport the frame across

the local media

how are collisions detected on an ethernet network?

the signal amplitude on the networking media is higher than normal

In cut-through switching

the switch acts upon the data as soon as it is received, even if,the transmission is not complete.

auto-MDIX feature is enabled

the switch detects the required cable type for copper Ethernet connections and configures the interfaces accordingly. Therefore,you can use either a crossover or a straight-through cable for connections to a copper 10/100/1000 port on the switch, regardless of the type of device on the other end of the connection.

Fragment-free switching

the switch stores the first 64 bytes of the frame before forwarding, because most network errors and collisions occur during the first 64 bytes.

broadcast

to find where PC2 is located, PC1 will send out a ____ data frame

binary is a base

two number system (0-1)

Layer 2 addressing provided by Ethernet supports

unicast, multicast, and broadcast communications.

PC2 will respond back to PC1 by sending back a _____message

unicast,,,

unicast MAC address is the

unique address used when a frame is sent from a single transmitting device to a single destination device.

Logical Link Layer (LLC) - handles the communication between the

upper layers (software) and the lower layers (hardware)

DHCP and Address Resolution Protocol (ARP)

use broadcasts.

Preable (7 bytes) and start of frame delimiter (1 byte)

used for synchronization between the sending and receiving devices

FCS field is

used to check errors in a frame

Frame Checksum Sequence (4 bytes)

used to detect errors in a frame

End devices requiring IP addresses include

user computers, servers, (printers, VOIP, VTC)

6- Ethernet Frame Field - 802.2 Header and data -

uses pad to increase this frame field to at least 64 bytes

Flooding

when switch does not have a destination MAC address in it's lookup table, it sends (floods) the frame out to all interfaces except the one in which teh frame arrived

Flooding

when switch does not have a destination MAC address in its lookup table, it sends the frame out to all interferences except teh one in which the frame arrived

store-and-forward switching

when the switch receives the frame, it stores the data in buffers until,the complete frame has been received, also performs a CRC

a Layer 3 switch can also learn

which IP addresses are associated with its interfaces, direct traffic throughout the network based on IP address information as well.

ARP

Address Resolution Protocol

A

B, C, and D are all connected to a HUB. A is sending stuff to D. B wants to send stuff to C. What must B do?,B must wait until it is certain that Host A has completed sending its frame

Decimal 0 =

Binary 0000

Decimal 2 =

Binary 0000 0010,

Decimal 4 =

Binary 0000 0100, ,

Decimal 8 =

Binary 0000 1000

Decimal 1 =

Binary 0001

Decimal 16 =

Binary 0001 0000,

Decimal 2 =

Binary 0010

Decimal 3 =

Binary 0010

Decimal 32 =

Binary 0010 0000,

Decimal 4 =

Binary 0011

Decimal 64 =

Binary 0100 0000,

Decimal 128 =

Binary 1000 0000,

Decimal 192 =

Binary 1100 0000

Decimal 202 =

Binary 1100 1010

Decimal 240 =

Binary 1111 0000

Decimal 255 =

Binary 1111 1111

Cisco devices which support Layer 3 switching utilize

Cisco Express Forwarding (CEF), and CEF decouples the usual strict interdependence between Layer 2 and Layer 3 decision making

"no switchport"-

Configure routed ports by putting the interface into Layer 3 mode

MAC sublayer responsibilities

Data encapsulation, Media access contol, addressing

Hexdecimal A = Binary 1010

Decimal 10

Hexdecimal 6 = Binary 0110

Decimal 6

Hexdecimal 7 = Binary 0111

Decimal 7

Hexdecimal 8 = Binary 1000

Decimal 8

Hexdecimal 9 = Binary 1001

Decimal 9

5- Ethernet Frame Field - Type/Length

Describes which higher level protocol has been used

Ethernet-IEEE-802.3 Frame-3

Destination Address (6)

7- Ethernet Frame Field - Frame Check Sequence

Detects errors in an ethernet frame

Multicast addresses allow a source device to send a packet to a group of devices

Devices that belong to a multicast group are assigned a multicast group IP address

Hexadecimal is used to represent

Ethernet MAC addresses and IP Version 6 addresses.

802.3 Ethernet-7

FCS,frame check sequence, detects errors in an ethernet frame (4 bytes)

which field used to detect errors in a frame

FCS-Frame Check Sequence, (4 bytes in length)

Ethernet broadcast MAC address is

FF-FF-FF-FF-FF-FF

FIB

Forwarding Information Base

Ethernet-IEEE-802.3

Frame-1,Preamble (7)

Ethernet-IEEE-802.3

Frame-2,Start of Frame Delimiter (1)

Ethernet-IEEE-802.3

Frame-4,Source Address (6)

Ethernet-IEEE-802.3

Frame-5,Length/Type (2)

Ethernet-IEEE-802.3

Frame-6,Data (46-1500)

Ethernet-IEEE-802.3

Frame-7,Frame Check Sequence (4)

LLC (logical link Layer)

Handles communication between the upper/lower layers, typical hardware

802.3 Ethernet-6

Header and data,uses pas to increase this frame to at least 64 bytes,

Binary 1011 =

Hexdecimal B

Binary 1100 =

Hexdecimal C

Binary 1101 =

Hexdecimal D

Binary 1110 =

Hexdecimal E

Binary 1111 =

Hexdecimal F

Source Address (6 bytes)

ID the frame's originating NIC or interface

Destination Address (6 bytes)

ID the intended recipient

4- Ethernet Frame Field - Source address -

The frame's originating NIC or interface MAC address

802.3 Ethernet-5

Type,describes which higher-level protocol has been used (2 bytes)

802.1Q

VLAN tag.

Length/Type (2 bytes)

Value equal to or greater than 0x0600 indicates the encapsulated protocol

IEEE 802.3ac

Virtual Local Area Network

a great method to use to conserve bandwidth on your network

store-and-forward,,,

network - most cabling will be

straight-through

Layer 3 interface is one that

supports forwarding IP packets toward a final destination based on the IP address.

Straight-Through UTP cable

switch-router; PC-to-switch; PC-to-HUB

crossover UTP

switch-switch, switch-to-hub, hub-hub, PC-PC, PC-router

decimal is a base

ten number system (0-9)

Historic Ethernet and Legacy Ethernet both use

logical bus topology

Fast-forward switching is the typical cut-through method of switching

lowest level of latency, immediately forwards a packet after reading the destination address.

Switch Frame Forwarding Method - Cut-Through

no error checking on frames is performed by the switch before rleeasing the frame out of its ports

1- Ethernet Frame Field - Preamble -

notifies destination to get ready for a new frame

Modular switches

offer more flexibility in their configuration,different sized chassis that allow for the installation of different numbers of modular line cards.

what is a limitation of legacy Ethernet technolgies

poor scalability

there are two methods of memory buffering

port-based and shared memory.

802.3 Ethernet-1

preamble,notifies destinations to get ready for a new frame (7 bytes)

do PC

printers, and routers have MAC addresses?,Yes

what is primary function of CSMA/CD in an ethernet network?

provides a method to determine when and how hosts access the Ethernet medium

IEEE 802.3ac standard

released in 1998, extended the maximum allowable frame size to 1522 bytes,becauseThe frame size was increased to accommodate a technology called Virtual Local Area Network (VLAN)

Network devices requiring IP addresses include

router LAN gateway interfaces, 2- router WAN (serial) interfaces

Timing more easily distorted with

shorter bit times

hexadecimal is a base

sixteen system (0-9,A-F)

802.3 Ethernet-4

source address,the frame originating NIC or interface MAC address (6 bytes)

routed port (behave like a Layer 3)

1-Is not associated with a particular VLAN, 2-Can be configured with a Layer 3 routing protocol, 3-Is a Layer 3 interface only and does not support Layer 2 protocol.

Two data link sublayers are

1-LLC and 2-MAC

Fast Ethernet SFP Modules -100BASE-FX (multimode fiber-optic (MMF)) for

2 kilometers (km)

Decimal 3

= Binary 0010,Hexdecimal 3

Decimal 4

= Binary 0011,Hexdecimal 4

Decimal 64

= Binary 0100 0000,Hexdecimal 40

Decimal 128

= Binary 1000 0000,Hexdecimal 80

Decimal 192

= Binary 1100 0000,Hexdecimal C0

Decimal 202

= Binary 1100 1010,Hexdecimal CA

Decimal 240

= Binary 1111 0000,Hexdecimal F0

Decimal 255

= Binary 1111 1111,Hexdecimal FF

Binary 1011

= Hexdecimal B,Decimal 11

Binary 1100

= Hexdecimal C,Decimal 12

Binary 1101

= Hexdecimal D,Decimal 13

Binary 1110

= Hexdecimal E,Decimal 14

Binary 1111

= Hexdecimal F,Decimal 15

Hexdecimal 6

=,Binary 0110

Hexdecimal 7

=,Binary 0111

Hexdecimal 8

=,Binary 1000

Hexdecimal 9

=,Binary 1001

Hexdecimal A

=,Binary 1010

Dropped frames are likely to be the result of

collisions or other unwanted signals and are therefore considered invalid.

"show ip arp"

command is used to display the ARP table-Cisco Router

802.2 Header and Data (46-1500 Bytes)

contains the encapsulated data from a higher layer

no error checking on frames is performed by the switch before releasing the frame out of it's ports

cut-through

ARP request?

host has a packet to send to an IP address that does not have a map in the ARP cache

Store-and-forward

if PC2 receives many damaged frames on Port 3, S1 likely will change back to ____ switching

Checks the frame for errors before releasing it out of its switch ports

if the full frame was not received, the switch discards it,store-and-forward,,

Connection to a switch port

is a separate collision domain

ARP poisoning/spoofing

is a technique used by an attacker to inject the wrong MAC address association into a network by issuing fake ARP requests.

802.3 Ethernet-2

start of frame delimiter,synchronez sending and receiving dvices for frme delivery (1 byte)

Buffers frames until the full frame has been received by the switch

store-and-forward

Broadcast Frame

1-Dest MAC (FF-FF-FF-FF-FF-FF),2-Source MAC, 3-Source IP, 4-Destination IP, 5- User Data, 6- Trailer

two variants of cut-through switching

1-Fast-forward switching, 2-Fragment-free switching:

two main components of CEF operation are the

1-Forwarding Information Base (FIB) and 2-Adjacency tables

Layer 3 switch can use both Layer 2 MAC addresses and IP address information.

...

multicast MAC address is a special value that begins with

01-00-5E in hexadecimal.

range of IPv4 multicast addresses is

224.0.0.0 to 239.255.255.255.

Fast Ethernet SFP Modules -100BASE-LX10 (single-mode fiber-optic (SMF)) for

2km

Ethernet address is a

48-bit binary value expressed as 12 hexdecimal digits

Ethernet Time Lengths

7-1-6-6-2-46/1500-4

Data Link - LLC -

802.2

3 standards used in Data and Physical Layers

802.2, 802.3, and DIX

Data Link-LAC-

802.3

Physical-MAC

802.3

Decimal 2

= Binary 0000 0010,Hexdecimal 02

Decimal 4

= Binary 0000 0100,Hexdecimal 04

Decimal 8

= Binary 0000 1000 ,Hexdecimal 08

Decimal 0

= Binary 0000,Hexdecimal 0

Decimal 16

= Binary 0001 0000,Hexdecimal 10

Decimal 1

= Binary 0001,Hexdecimal 1

Decimal 32

= Binary 0010 0000,Hexdecimal 20

Decimal 2

= Binary 0010,Hexdecimal 2

which layer 2 sublayer provides services to the network layer of the OSI model

LCC

Controls the network interface card through software drivers

LCC,

Works with the upper layers to add application information for deliverey of data to higher level protocols

LCC,,,

Reamins relatively independent of physical equipment

LCC....

Collision domans occur at

Layer 1 of the networking reference model

LLC

Logical Link Layer

Layer 3-EtherChannel -

Logical interface on a Cisco device associated with a bundle of routed ports.

Layer 3-Switch Virtual Interface (SVI) -

Logical interface on a switch associated with a virtual local area network (VLAN).

Works with hardware to support bandwidth requirements - checks for errors in bits sent and received

MAC

Controls access to the media through signalling and physical media standards requirements

MAC,,,

Supports Ethernet technology by using CSMA/CD and CSMA/CA

MAC....

what is the MAC address for a HUB?

None

Layer 2 LAN switch performs switching and filtering based only on the

OSI data link layer (Layer 2) MAC address and depends upon routers to pass data between independent IP subnetworks

A Layer 2 LAN switch performs switching and filtering based only on the

OSI data link layer (Layer 2) MAC address, builds a MAC address table that it uses to make forwarding decisions

Layer 3-Routed Port -

Physical port on a Layer 3 switch configured to act as a router port.

PoE

Power over Ethernet

2- Ethernet Frame Field - Start of Frame delimiter

Synchronizes sending and receiving devices for frame delivery

Ethernet II is the Ethernet frame format used in

TCP/IP networks

cut-through switch forwards the frame before

it is totally received...at a minium the destination address of the frame must be read before the frame can be forwarded

If PC2 receives only half of the data in the frame

it will _____,discard it

stage of operation of an ethernet switch that creates MAC table entries

learning

The group of connected devices that can cause collisions to occur with each other is known as

a collision model

Shared memory buffering deposits all frames into

a common memory buffer that all the ports on the switch share, amount of buffer memory required by a port is dynamically allocated

The jam signal in CSMA/CD makes ure that

all sending nodes see the collision

The jam signal in CSMA/CD makes sure that

all sending nodes see the collison

Frames with FF-FF-FF-FF-FF-FF

are delievered to and processed by all devices on that LAN segment

3- Ethernet Frame Field - Destination address -

assists a host in determining if the frame received is addressed to it

MAC addresses are used to identify

at a lower level,the source and destination hosts, it sends frames containing its own MAC address as the source and the MAC address of the intended recipient as the destination.

ipconfig /all command can

be used to identify the MAC address of an Ethernet adapter.

Historic Ethernet and legacy Ethernet

both use logical bus topology

Switch Frame Forwarding Method - Store-and-Forward

buffers frames until the full frame has been received by the switch

the faster switching method

but may produce more errors in data integrity - therefore more bandiwtdh may be consumed,cut-through method,,,,

FIB similar to a routing table

but,uses the FIB lookup table to make destination-based switching decisions without having to access the route cache

Switch Frame Forwarding Method - Store-and-Forward

checks the frame for errors befoe rleeasing it out of the switch ports - if the full frame was not received, the switch discards

destination NIC disacrds any incomplete frames using this frame forwrading method

cut-through method

Layer 2 switches

depend on routers to pass data between independent IP subnetworks.

what address type does a switch use to make selective forwarding decisions

destination MAC

802.3 Ethernet-3

destination address,assists a host in detremining if the frame receeiving is addressed to it (6 bytes)

What is the purpose of media access control?

determines which workstation on a shared medium LAN is allowed to transmit data

"arp -a" command is used to

display the ARP table- Windows 7 PC

100BASE-FX uses fiber cabling and supports full duplex upto

distance of 2000 meteres

Stackable switches- connected by a special cable

effectively operate as one large switch

Switch Frame Forwarding Method

faster switching method - but may produce more errors in data integrity - more bandwidth may be consumed

Fixed configuration switches

fixed in their configuration,you cannot add features or options to the switch beyond those that originally came with the switch.

Fast Ethernet SFP Modules -100BASE-BX10 (SMF)

for 10 km

Fast Ethernet SFP Modules -100BASE-EX (SMF)

for 40 km

Fast Ethernet SFP Modules -100BASE-ZX (SMF)

for 80 km

In port-based memory buffering

frames are stored in queues that are linked,to specific incoming and outgoing ports. frame is transmitted to the outgoing port only when all the frames ahead of it in the queue have been successfully transmitted.

why higher speed ethernet implementations more susceptible to noise

full-duplex operation

Switch Frame Forwarding Method - Store-and-Forward

great method to use to conserve bandwdith on your network

Collision Domain

group of connected devices that can cause collisions to occur with each other, happens at layer 1

broadcast packet contains a destination IP address that

has all ones (1s) in the host portion, means that all hosts on that local network (broadcast domain) will receive and process the packet.

MAC addresses use

hexadecimal numbering, convenient way to represent binary values

40 Gigabit Ethernet and 100 Gigabit Ethernet modules are supported on

high-end Cisco devices