Download CCNA 1 Module 10 Routing Fundamentals and Subnets

CCNA 1 Chapter 8
Routing Fundamentals and
Subnets
By
Joe Parisien
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Objectives
• Routed protocol
• IP routing protocols
• The mechanics of subnetting
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Routed Protocols Versus
Routing Protocols
Routing protocols determine the path that routed
protocols follow to their destinations.
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Characteristics of a
Routable Protocol
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IP as a Routed Protocol
• IP is a connectionless,
unreliable, best-effort
delivery protocol.
• As information flows
down the layers of the
OSI model; the data is
processed at each layer.
• IP accepts whatever data
is passed down to it from
the upper layers.
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Packet Propagation
Each router provides its services to
support upper-layer functions.
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Connectionless Network Services
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Connection-Oriented
Network Services
A connection is established between the
sender and the recipient before any data is
transferred.
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Anatomy of an IP Packet
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Version
IP header length (HLEN)
Type-of-service
Total length
Identification
Flags
Fragment offset
Time-to-live
Protocol
Header checksum
Source address
Destination address
Options
Padding
Data
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Routing Protocols
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Router Overview
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Layer 3 Addresses
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Routing Versus Switching
• This distinction is routing and switching use
different information in the process of moving
data from source to destination.
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Routed Versus Routing
• A routed protocol:
– Includes any network protocol suite that provides
enough information in its network layer address to
allow a router to forward it to the next device and
ultimately to its destination.
– Defines the format and use of the fields within a
packet.
• A routing protocol:
– Provides processes for sharing route information.
– Allows routers to communicate with other routers to
update and maintain the routing tables.
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Path Determination
• Path determination enables a router to compare
the destination address to the available routes in
its routing table, and to select the best path.
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Routing Tables
• Routers keep track of the following:
– Protocol type
– Destination/next-hop associations
– Routing metric
– Outbound interfaces
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Routing Algorithms and Metrics
• Routing protocols have one or more of the following design
goals:
– Optimization
– Simplicity and low overhead
– Robustness and stability
– Flexibility
– Rapid convergence
• Metrics most commonly used by routing protocols include the
following:
– Bandwidth
– Delay
– Load
– Reliability
– Hop count
– Ticks
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– Cost
RIP and IGRP
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IGP and EGP
• IGPs route data within an autonomous system.
• EGPs route data between autonomous systems.
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Link State and Distance Vector
• Examples of distance-vector protocols:
– Routing Information Protocol (RIP)
– Interior Gateway Routing Protocol (IGRP)
– Enhanced IGRP (EIGRP)
• Examples of link-state protocols:
– Open Shortest Path First (OSPF)
– Intermediate System-to-Intermediate System (IS-IS)
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Routing Protocols
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RIP
RIP v2
IGRP
EIGRP
OSPF
IS-IS
BGP
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Mechanics of Subnetting
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Classes of Network IP Addresses
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Subnetworks
To create a subnet address, a network
administrator borrows bits from the original host
portion and designates them as the subnet field.
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Subnetworks
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Subnet Mask
• Determines which part of an IP address is the
network field and which part is the host field.
• Follow these steps to determine the subnet mask:
1. Express the subnetwork IP address in binary form.
2. Replace the network and subnet portion of the address
with all 1s.
3. Replace the host portion of the address with all 0s.
4. Convert the binary expression back to dotted-decimal
notation.
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Subnet Mask
Subnet mask in decimal = 255.255.240.0
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Subnet Addresses
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Determining Subnet Mask Size
Class B address with 8 bits borrowed for the subnet
130.5.2.144 (8 bits borrowed for subnetting) routes to subnet
130.5.2.0 rather than just to network 130.5.0.0.
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Determining Subnet Mask Size
Class C address 197.15.22.131 with a subnet
mask of 255.255.255.224 (3 bits borrowed)
11000101 00001111 00010110 100
Network Field
SN
00011
Host
Field
The address 197.15.22.131 would be on the
subnet 197.15.22.128.
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Subnetting Example
with AND Operation
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