ccna 200-120

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the source and destination MAC changes as each router hop along with the TTL

being decrementedbut the source and destination IP address remain the same from source to

destination.

If Subnet Mask is 2.2.2.!2" the hosts #ar$ from %.%.%.& ' %.%.%.!2( ) %.%.%.!2"'%.%.%.2*so the IP Addresses of 2 hosts fall in different subnets so each interface needsan IP an address so that the$ can communicate each other.

If Subnet Mask is 2.2.2.& the 2 specified hosts fall in different subnets so the$need a La$er + de#ice to communicate.

If Subnet Mask is 2.2.2,.& the 2 specified hosts are in same subnet so are innetwork address and can be accommodated in same La$er 2 domain and can

communicate with each other directl$ using the La$er 2 address.

The Application la$er is responsible for identif$ing and establishing the a#ailabilit$ of theintended communication partner and determining whether sufficient resources for theintended communication e%ist.

The idea behind a -A is to be able to connect two /T0 networks together through a/C0network. The network1s /C0 de#ice includes CS34/S35 pro#ides clocking to the /T0'connected

interface the router1s serial interface5.

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-hen a host needs to reach a de#ice on another subnet* the A6P cache entr$ will be

that of the 0thernet address of the local router default gatewa$5 for the ph$sical MACaddress. The destination IP address will not change* and will be that of the remote host7ost85.

Modern 0thernet networks built with switches and full'duple% connections no longerutili9eCSMA4C/. CSMA4C/ is onl$ used in obsolete shared media 0thernet which usesrepeater or hub5.

the source MAC address of the frames recei#ed b$ 7ost A from the ser#er.

the MAC address of router interface e&

Switches break up collision domains* while routers and :LAs5 break up

collision domains and broadcast domains. Also* a broadcast domain can containmultiple collision domains* but a collision domain can ne#er ha#e more than onebroadcast domain associated with it.

La$er 2 0thernet switches; 0stablishing :LAs increases the number of broadcast domains.

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Microsegmentation decreases the number of collisions on the network.

In a properl$ functioning network with redundant switched paths* each switched

segment will contain one root bridge with all its ports in the forwarding state. Allother switches in that broadcast domain will ha#e onl$ one root port.

Increases the number of collision domains.

Internet La$er of TCP4IP is e<ui#alent to the etwork La$er which is responsible forrouting decision.

MAC addresses; identif$ de#ices at la$er 2.

used to communicate on the same network

To communicate on different network we ha#e to use La$er + addresses

La$er 2 frame and La$er + packet can be recogni9ed #ia headers. La$er + packet

also contains ph$sical address

=n 0thernet* each frame has the same priorit$ to transmit b$ default '>

All de#ices need a ph$sical address to identif$ itself. If not* the$ can not

communicate

0lect the root bridge;

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?irst check the priorit$ #alue. The switch ha#ing the lowest priorit$ will win the

election process. If Priorit$ :alue is the same then it checks the MAC Address@ the switch ha#ing

the lowest MAC Address will become the root bridge.

=nl$ router can break up broadcast domains so in the e%hibit there are 2

broadcast domains; from e& interface to the left is a broadcast domain and frome! interface to the right is another broadcast domain '>.

8oth router and switch can break up collision domains so there is onl$ ! collision

domain on the left of the router because hub doesn1t break up collision domain5

and there are collision. domains on the right of the router ! collision domainfrom e! interface to the switch B collision domains for PCs in Production5

0thernet network; 0thernet network is a shared en#ironment so all de#ices ha#e the right to access

to the medium. If more than one de#ice transmits simultaneousl$* the signalscollide and can not reach the destination.

If a de#ice detects another de#ice is sending* it will wait for a specified amount of

time before attempting to transmit.

-hen there is no traffic detected* a de#ice will transmit its message. -hile thistransmission is occurring* the de#ice continues to listen for traffic or collisions onthe LA. After the message is sent* the de#ice returns to its default listeningmode.

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A router on a stick allows $ou to use sub'interfaces to create multiple logical networkson a singleph$sical interface.

7ost ! is tr$ing to communicate with 7ost 2. The e& interface on 6outer C is down.6outer C will send ICMP packets to inform 7ost ! that 7ost 2 cannot be reached.

CS34/S3 is used to con#ert digital signals from a router to a network circuit such

as a T!* Modem is used to con#ert digital signals o#er a regular P=TS line.

Straight'through cable to connect switch to router* switch to host* hub to host

Crosso#er cable to connect switch to switch* switch to hub* router to router* host to host.

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Source Mac Address /estination Mac Address Source IP address /estination MACaddress MAC &&&&.&c".++++ MAC &&&&.&c". IP !(2.!.+,.2& IP !(2.!.2!.(

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LAN Switching Technologies

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Switch port ?ast0thernet &42, on ALSwitch! will be used to create an I000 "&2.!D'compliant trunk to another switch. 8ased on the output shown* what is the reason thetrunk does not form* e#en though the proper cabling has been attachedE

According to the output shown the switchport la$er 2 Switching5 is enabled and the portis in access mode. To make a trunk link the port should configured as a trunk port* notan access port*b$ using the following command; Config'if5Fswitchport mode trunk

6apid'P:ST; P:STB is based on I000"&2.!/ Spanning Tree Protocol STP5.

8ut P:STB has onl$ + port states

discarding* learning and forwarding5

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STP has port states ;

blocking* listening* learning*forwarding and disabled5.

So discarding is a new port state in P:STB.

:LA + is not $et configured on $our switch. -hat happens if $ou set the switchportaccess #lan + command in interface configuration modeE

Accepted and the respecti#e :LA is added to #lan.dat.

6oot port;the port with lowest cost to the root bridge will become root port on non'root switch5

The abo#e MAC'add is not present in MAC table.Then

Switch'! will flood the data out all of its ports e%cept the port from which the data

originated In output there is no MAC address of gi#e host so switch floods to all ports

e%cept the source port. switchport trunk nati#e #lan ; Configuring the ati#e :LA for 3ntagged

Traffic

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A trunk port configured with "&2.!D tagging can recei#e both tagged and

untagged traffic. 8$ default* the switch forwards untagged traffic in the nati#e:LA configured for the port. The nati#e :LA is :LA ! b$ default.

-hich two protocols are used b$ bridges and4or switches to pre#ent loops in a la$er 2networkE

"&2.!d

STP

0ach :LA creates its own broadcast domain. Since this is a full duple% switch*

each port is a separate collision domain

6oot bridge; 8ridge priorit$ B MAC

Benefits of VLANs:

Inexpensive

Better management

Improves network security

nhances performance

Segment multiple networks

Better a!ministration

/$namic Trunking Protocol /TP5 is a Cisco proprietar$ protocol for negotiating

trunking on a link between two de#ices and for negotiating the t$pe of trunking

encapsulation "&2.!D5 to be used.

-hen using :LA the number and si9e of collision domains remain the same '>

:LAs allow to group users b$ function* not b$ location or geograph$ '> .

:LAs help minimi9e the incorrect configuration of :LAs so it enhances the

securit$ of the network '> .

:LA increases the si9e of broadcast domains but does not decrease the

number of collision domains '>

:LAs increase the number of broadcast domains while decreasing the si9e of

the broadcast domains which increase the utili9ation of the links. It is also a bigad#antage of :LA '>.

:LAs are useful but the$ are more comple% and need more administration '>

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A technician has installed Switch8 and needs to configure it for remote access from themanagement workstation connected to SwitchA. -hich set of commands is re<uired toaccomplish this taskE

Intersubnetwork communication;

Switch8config5F ip default'gatewa$ !2.!".".2,Switch8config5F interface #lan !Switch8config'if5F ip address !2.!".".22 2.2.2.&

6STP port states; /iscarding

forwarding

Trunk :erification commands; show interface trunk

show interface fast &42 switchport Gname>

6STP "&2.!w5 enable on a switch; spanning'tree mode rapid'p#st

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All switch ports are assigned to the correct :LAs* but none of the hosts connected toSwitchA can communicate with hosts in the same :LA connected to Switch8. 8asedon the output shown* what is the most likel$ problemE

In order to pass traffic from :LAs on different switches* the connections

between the switches must be configured as trunk ports.

data link protocol used in this network is the ?rame 6ela$ protocol.

HLMI en< sentJ

Switches d$namicall$ learn MAC addresses based on the source MAC

addresses

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The root bridge is determined b$ the lowest bridge I/* and this switch has a

bridge I/ priorit$ of +2("* which is higher than the roots priorit$ of 2&,"!.

which :LA range can be added* modified* and remo#ed on a Cisco switchE

6ange 2 through !&&!

:LA ! is the default :LA on Cisco switch. It alwa$s e%ists and can not beadded* modified or remo#ed.

:LAs !&&2'!&& are default :LAs for ?//I ) Token 6ing and the$ can1t be

deleted or used for 0thernet.

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3nknown unicast frames are retransmitted onl$ to the ports that belong to the

same :LA.

/esignated Port;

Compare the path cost* if the costs happen to be the same* Then compare the 8I/* still the smallest will be selected

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nati#e :LA mismatches

3ntagged frames are encapsulated with the nati#e :LA. In this case* the nati#e

:LAs are different so although S! will tag it as :LA ! it will be recei#ed b$ S2.

"ST# are true: 6STP significantl$ reduces topolog$ recon#erging time after a link failure.

STP e%pands the STP port roles b$ adding the alternate and backup roles.

6STP pro#ides a faster transition to the forwarding state on point'to'point links

than STP does.

6STP bridge port roles;

6P

/P

Alternate port

Backup port

$isa%le! port

La$er 2 switch use to decide where to forward a recei#ed frame based

destination mac'add.

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If the address is unknown* the frame is broadcast on all

interfaces e%cept the one it was recei#ed on.

sw! is the root bridge.

The root port 6P5 is the port that leads to the root bridge so the root bridge does not

ha#e an$ root ports.

All the ports on a root bridge forward and the$ are all designated ports /P5.

As $ou can see there is loop in this the abo#e network so one of the links must be

blocked 8LK5.

"&2.!D protocol; It modifies the "&2.+ frame header* and thus re<uires that the ?CS be

recomputed.

It is a trunking protocol capable of carr$ing untagged frames.

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The network administrator normall$ establishes a Telnet session with the switch fromhost A.7owe#er* host A is una#ailable. The administrators attempt to telnet to the switchfrom host 8 fails* but pings to the other two hosts are successful. -hat is the issueE

Ping was successful form host 8 to other hosts because of inter#lan routing configuredon router.8ut to manage switch #ia telnet the :LA+2 on the switch needs to beconfigured interface #lan+2 along with ip address and its appropriate default'gatewa$address. Since :LA! interface is alread$ configure on switch 7ost A was able to telnetswitch.

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-hich switch pro#ides the spanning'tree designated port role for the network segmentthat ser#ices the printersE

P:STB allows the root switch location to be optimi9ed per :LA.

The P:STB pro#ides La$er 2 load'balancing for the :LA0ach instance of P:STB on a :LA has a single root switch. This root switchpropagates the spanning'tree information to all other switches in the network. 8ecauseeach switch has the same information about the network*this process ensures that the network topolog$ is maintained and optimi9ed per :LA.6eference;

/ifferent t$pes of trunk modes;

Auto

=n

/isable

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7ow man$ broadcast domains are shown in the graphic assuming onl$ the default:LA is configured on the switchesE

=nl$ router can break up broadcast domains but in this e%hibit no router is used

so there is onl$ ! broadcast domain.

?or $our information* there are ( collision domains in this e%hibit collision

domains between hubs ) switches B ! collision between the two switches5.

&'()*+ trunking: "&2.!D nati#e :LA frames are untagged b$ default.

"&2.!D trunks can use !& Mb4s 0thernet interfaces.

"&2.!D trunks should ha#e nati#e :LAs that are the same at both ends.

The output that is shown is generated at a switch. -hich three statements are trueE

All ports will be in a state of discarding* learning* or forwarding.

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The bridge priorit$ is lower than the default #alue for spanning tree.

All designated ports are in a forwarding state.

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ccna 200-120