ccnav3.3 110
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CCNA Semester 1
Chapter 10Chap
ter 10
LAYER 3LAYER 3
PROTOCOLSPROTOCOLS
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LAYER 3 DEVICESLAYER 3 DEVICES
ANDAND
NETWORK TO NETWORKNETWORK TO NETWORK
COMMUNICATIONCOMMUNICATION
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InternetworkingInternetworking
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Path determinationPath determination
Path determination is the process that therouter uses to choose the next hop in thepath for the packet to travel to itsdestination based on the link bandwidth,
hop, delay ...
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RouterRouter
A router is a type of internetworking device
that passes data packets betweennetworks, based on Layer 3 addresses.
A router has the ability to make intelligentdecisions regarding the best path fordelivery of data on the network.
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IP addressesIP addresses
IP addresses are implemented in software,and refer to the network on which a device
is located.
IP addressing scheme, according to theirgeographical location, department, or floor
within a building. Because they are implemented in software,
IP addresses are fairly easy to change.
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Router and BridgeRouter and Bridge
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Router connectionsRouter connections
Routers connect two or more networks,
each of which must have a unique networknumber in order for routing to besuccessful.
The unique network number is incorporatedinto the IP address that is assigned to eachdevice attached to that network.
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Router InterfaceRouter Interface
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Router functionRouter function
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Router function (cont.1)Router function (cont.1)
Strips off the data link header,
carried by the frame.(The data link header contains the
MAC addresses of the source and
destination.)
Strips off the data link header,
carried by the frame.(The data link header contains the
MAC addresses of the source and
destination.)
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Router function (cont.2)Router function (cont.2)
Examines the network layeraddress to determine the
destination network.
Examines the network layeraddress to determine the
destination network.
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Router function (cont.3)Router function (cont.3)
Consults its routing tables to
determine which of its interfaces itwill use to send the data, in order
for it to reach its destination
network.
Consults its routing tables to
determine which of its interfaces itwill use to send the data, in order
for it to reach its destination
network.
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Router function (cont.4)Router function (cont.4)
Send the data out interface B1, therouter would encapsulate the data
in the appropriate data link frame.
Send the data out interface B1, therouter would encapsulate the data
in the appropriate data link frame.
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Router Interface exampleRouter Interface example
Interface is a routers attachment to anetwork, it may also be referred to as aport. In IP routing.
Each interface must have a separate,
unique network address.
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IP address assignmentIP address assignment
static addressing and dynamic addressing
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Static addressingStatic addressing
You must go to each individual device andconfigure it with an IP address.
You should keep very meticulous records,because problems can occur on the
network if you use duplicate IP addresses.
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Dynamic addressingDynamic addressing
There are a few different methods that youcan use to assign IP addresses dynamically:
RARP: Reverse Address Resolution Protocol.
BOOTP: BOOTstrap Protocol.
DHCP: Dynamic Host Configuration Protocol.
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Dynamic addressing:Dynamic addressing: RARPRARP
MAC:MAC: KnownKnown
IP:IP: UnknownUnknown
MAC:MAC: KnownKnown
IP:IP: UnknownUnknown
RARP RequestRARP Request
RARP ReplyRARP Reply
RARP serverRARP server
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Dynamic addressing:Dynamic addressing: BOOTPBOOTP
MAC:MAC: KnownKnown
IP:IP: UnknownUnknown
MAC:MAC: KnownKnown
IP:IP: UnknownUnknown
UDP BroadcastUDP Broadcast
UDP BroadcastUDP Broadcast
BOOTP serverBOOTP server
MACMAC11 IP IP11
MACMAC22 IP IP22
MACMAC33 IP IP33
MACMAC11 IP IP11
MACMAC22 IP IP22
MACMAC33 IP IP33
IP AddressIP Address
IP of serverIP of server
Vendor-specificVendor-specific
IP AddressIP Address
IP of serverIP of serverVendor-specificVendor-specific
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Dynamic addressing:Dynamic addressing: DHCPDHCP
MAC:MAC: KnownKnownIP:IP: UnknownUnknownMAC:MAC: KnownKnownIP:IP: UnknownUnknown
DHCP DiscoverDHCP DiscoverUDP BroadcastUDP Broadcast
DHCP OfferDHCP Offer
UDP BroadcastUDP Broadcast
DHCP serverDHCP server
IPIP11
IPIP22
IPIP33
IPIP11
IPIP22
IPIP33
DHCP RequestDHCP Request
DHCP AckDHCP Ack
IP AddressIP Address
GatewayGateway
IP of serversIP of servers
And more And more
IP AddressIP Address
GatewayGateway
IP of serversIP of servers
And more And more
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ARP CONCEPTARP CONCEPT
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EncapsulationEncapsulation
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Address resolution protocolAddress resolution protocol
In order for devices to communicate, thesending devices need both the IP addressesand the MAC addresses of the destination
devices. When they try to communicate with devices
whose IP addresses they know, they mustdetermine the MAC addresses.
ARP enables a computer to find the MACaddress of the computer that is associatedwith an IP address.
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Address resolution protocolAddress resolution protocol
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ARP table in hostARP table in host
RAM
RAM
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10.0.2.1
A.B.C.1.2.3
10.0.2.9
A.B.C.7.8.9
10.0.2.5
A.B.C.4.5.6
AA BB CC
ARP operationARP operation
ARP Table:
? MACA.B.C.1.2.3
MAC
?IP
10.0.2.1
IP
10.0.2.9Data
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10.0.2.1
A.B.C.1.2.3
10.0.2.9
A.B.C.7.8.9
10.0.2.5
A.B.C.4.5.6
AA BB CC
ARP operation:ARP operation: ARP requestARP request
MAC
A.B.C.1.2.3
MAC
ff.ff.ff.ff.ff.ff
IP
10.0.2.1
IP
10.0.2.9What is your MAC Addr?
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10.0.2.1
A.B.C.1.2.3
10.0.2.9
A.B.C.7.8.9
10.0.2.5
A.B.C.4.5.6
AA BB CC
ARP operation:ARP operation: CheckingChecking
MAC
A.B.C.1.2.3
MAC
ff.ff.ff.ff.ff.ff
IP
10.0.2.1
IP
10.0.2.9What is your MAC Addr?
Thatis
Thati
s
myIP
myIP
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10.0.2.1
A.B.C.1.2.3
10.0.2.9
A.B.C.7.8.9
10.0.2.5
A.B.C.4.5.6
AA BB CC
ARP operation:ARP operation: ARP replyARP reply
MAC
A.B.C.7.8.9
MAC
A.B.C.1.2.3
IP
10.0.2.9
IP
10.0.2.1This is my MAC Addr
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10.0.2.1
A.B.C.1.2.3
10.0.2.9
A.B.C.7.8.9
10.0.2.5
A.B.C.4.5.6
AA BB CC
ARP operation:ARP operation: CachingCaching
ARP Table:
A.B.C.7.8.9 10.0.2.9
MAC
A.B.C.1.2.3
MAC
A.B.C.7.8.9
IP
10.0.2.1
IP
10.0.2.9Data
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ARP:ARP: Destination localDestination local
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Internetwork communicationInternetwork communication
How to communicate with devices that arenot on the same physical network segment.
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Default gatewayDefault gateway
In order for a device to communicate withanother device on another network, youmust supply it with a default gateway.
A default gateway is the IP address of theinterface on the router that connects to thenetwork segment on which the source host islocated.
In order for a device to send data to theaddress of a device that is on anothernetwork segment, the source device sendsthe data to a default gateway.
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Proxy ARPProxy ARP
Proxy ARP is a variation of the ARP.
In the case the source host does not have a
default gateway configured.
ARPReply
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ARP:ARP: Destination not localDestination not local
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ARP FlowchartARP Flowchart
Send Datato a device
Send Data
Send an
ARP request
Get an
ARP reply
Is theMAC address
in my ARP
cache
NN
YY
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ARP table in routerARP table in router
The router interface connected to thenetwork has an IP address for that network.
Routers, just like every other device on thenetwork, send and receive data on thenetwork.
If router connects to a LAN, it builds ARPtables that maps IP addresses to MACaddresses in that interface.
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ARP table in routers and in hostsARP table in routers and in hosts
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Preparation for LABPreparation for LAB
Lab:
Protocol inspector and ARP
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ROUTED AND ROUTING PROTOCOLSROUTED AND ROUTING PROTOCOLS
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Network protocolsNetwork protocols
In order to allow two host communicate
together through internetwork, they need asame network protocol.
Protocols are like languages.
IP is a network layer protocol.
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Network protocol operationNetwork protocol operation
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Routed protocolRouted protocol
Protocols that providesupport for thenetwork layer are
called routed orroutable protocols.
IP is a network layerprotocol, and becauseof that, it can berouted over aninternetwork.
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Protocol addressing variationsProtocol addressing variations
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Three important routed protocolsThree important routed protocols
TCP/IP: 04 bytes
Class A: 1 byte network + 3 bytes host
Class B: 2 bytes network + 2 bytes host Class C: 3 bytes network + 1 byte host
IPX/SPX: 10 bytes
4 bytes network + 6 bytes host
AppleTalk: 03 bytes
2 bytes network + 1 byte host
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Non-routable protocolNon-routable protocol
Non-routable protocols areprotocols that do notsupport Layer 3.
The most common of thesenon-routable protocols isNetBEUI.
NetBEUI is a small, fast,and efficient protocol thatis limited to running onone segment.
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Addressing of a routable protocolAddressing of a routable protocol
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Routing tableRouting table
131.108.1.0 E0
131.108.2.0 E1
131.108.3.0 E2
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Multi-protocol routingMulti-protocol routing
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Classification #1:Classification #1: Static and DynamicStatic and Dynamic
Static routes:
The network administrator manually enter therouting information in the router.
Dynamic routes:
Routers can learn the information from eachother on the fly.
Using routing protocol to update routinginformation.
RIP, IGRP, EIGRP, OSPF
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Static routesStatic routes
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Dynamic routesDynamic routes
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Static vs. dynamic routesStatic vs. dynamic routes
Static routes:
For hiding parts of an internetwork.
To test a particular link in a network.
For maintaining routing tables whenever there is only onepath to a destination network.
Dynamic routes:
Maintenance of routing table.
Timely distribution of information in the form of routingupdates.
Relies on routing protocol to share knowledge.
Routers can adjust to changing network conditions.
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Routing protocolRouting protocol
Routing protocolsdetermine the paths thatrouted protocols follow to
their destinations.
Routing protocols enablerouters that are connected
to create a map, internally,of other routers in thenetwork or on the Internet.
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Routed vs. Routing protocolRouted vs. Routing protocol
Rou
tingp
rotoc
ols
Rou
tingp
rotoc
ols
determi
neho
wrou
ted
determine
howr
outed
proto
colsarer
outed
protoc
olsare
routed
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Classification #2:Classification #2: IGP and EGPIGP and EGP
Dynamic routes.
Interior Gateway Protocols (RIP, IGRP, EIGRP, OSPF):
Be used within an autonomous system, a network ofrouters under one administration, like a corporate network,a school district's network, or a government agency'snetwork.
Exterior Gateway Protocols (EGP, BGP): Be used to route packets between autonomous systems.
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IGPIGP
IGPIGP
IGP vs. EGPIGP vs. EGP
EGPEGP
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Classification #3:Classification #3: DVP and LSPDVP and LSP
Distance-Vector Protocols (RIP, IGRP):
View network topology from neighbors perspective.
Add distance vectors from router to router.
Frequent, periodic updates.
Pass copy of routing tables to neighbor routers.
Link State Protocols (OSPF):
Gets common view of entire network topology.
Calculates the shortest path to other routers.
Event-triggered updates.
Passes link state routing updates to other routers.
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Distance vector routingDistance vector routing
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Link state routingLink state routing
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RIPRIP
Most popular.
Interior Gateway Protocol.
Distance Vector Protocol.
Only metric is number of hops.
Maximum number of hops is 15.
Updates every 30 seconds. Doesnt always select fastest path.
Generates lots of network traffic.
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IGRP and EIGRPIGRP and EIGRP
Cisco proprietary.
Interior Gateway Protocol.
Distance Vector Protocol.
Metric is compose of bandwidth, load, delayand reliability.
Maximum number of hops is 255.
Updates every 90 seconds. EIGRP is an advanced version of IGRP, that
is hybrid routing protocol.
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OSPFOSPF
Open Shortest Path First.
Interior Gateway Protocol. Link State Protocol.
Metric is compose of cost, speed, traffic,reliability, and security.
Event-triggered updates.
Q&A
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Q&AQ&A
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