Transcript CCNA 1 Module 10 Routing Fundamentals and

CCNA 1 Chapter 8
Routing Fundamentals and
Subnets
By
Your Name
Copyright 2003
www.ciscopress.com
Objectives
• Routed protocol
• IP routing protocols
• The mechanics of subnetting
Copyright 2003
www.ciscopress.com
Routed Protocols Versus
Routing Protocols
Routing protocols determine the path that routed
protocols follow to their destinations.
Copyright 2003
www.ciscopress.com
Characteristics of a
Routable Protocol
Copyright 2003
www.ciscopress.com
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.
Copyright 2003
www.ciscopress.com
Packet Propagation
Each router provides its services to
support upper-layer functions.
Copyright 2003
www.ciscopress.com
Connectionless Network Services
Copyright 2003
www.ciscopress.com
Connection-Oriented
Network Services
A connection is established between the
sender and the recipient before any data is
transferred.
Copyright 2003
www.ciscopress.com
Anatomy of an IP Packet
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
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
Copyright 2003
www.ciscopress.com
Routing Protocols
Copyright 2003
www.ciscopress.com
Router Overview
Copyright 2003
www.ciscopress.com
Layer 3 Addresses
Copyright 2003
www.ciscopress.com
Routing Versus Switching
• This distinction is routing and switching use
different information in the process of moving
data from source to destination.
Copyright 2003
www.ciscopress.com
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.
Copyright 2003
www.ciscopress.com
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.
Copyright 2003
www.ciscopress.com
Routing Tables
• Routers keep track of the following:
– Protocol type
– Destination/next-hop associations
– Routing metric
– Outbound interfaces
Copyright 2003
www.ciscopress.com
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
Copyright
2003
www.ciscopress.com
– Cost
RIP and IGRP
Copyright 2003
www.ciscopress.com
IGP and EGP
• IGPs route data within an autonomous system.
• EGPs route data between autonomous systems.
Copyright 2003
www.ciscopress.com
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)
Copyright 2003
www.ciscopress.com
Routing Protocols
•
•
•
•
•
•
•
Copyright 2003
RIP
RIP v2
IGRP
EIGRP
OSPF
IS-IS
BGP
www.ciscopress.com
Mechanics of Subnetting
Copyright 2003
www.ciscopress.com
Classes of Network IP Addresses
Copyright 2003
www.ciscopress.com
Subnetworks
To create a subnet address, a network
administrator borrows bits from the original host
portion and designates them as the subnet field.
Copyright 2003
www.ciscopress.com
Subnetworks
Copyright 2003
www.ciscopress.com
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.
Copyright 2003
www.ciscopress.com
Subnet Mask
Subnet mask in decimal = 255.255.240.0
Copyright 2003
www.ciscopress.com
Subnet Addresses
Copyright 2003
www.ciscopress.com
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.
Copyright 2003
www.ciscopress.com
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.
Copyright 2003
www.ciscopress.com
Subnetting Example
with AND Operation
Copyright 2003
www.ciscopress.com