Routing in Internet Protocol networks.ppt

Routing in IP networks

1. CCNA Guide to Cisco
Networking Fundamentals
Fourth Edition
Chapter 7
Routing Protocols

2. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 2
Objectives
•Differentiate between nonroutable, routed, and
routing protocols
•Define Interior Gateway Protocols, Exterior Gateway
Protocols, distance-vector routing protocols, and link-
state routing protocols
•Explain the concepts of count-to-infinity, split
horizon, split horizon with poison reverse, and hold-
down timers

3. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 3
Objectives (continued)
•Describe, configure, and monitor the interior routing
protocol RIP
•Explain static routing and administrative distance
•Configure static routing and default routes

4. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 4
Nonroutable Protocols
•In the early days of networking, networks were small
collections of computers linked together
–For the purposes of sharing information and expensive
peripherals
•Early networks were sometimes configured as peer-
to-peer networks
–Computers communicate with and provide services to
their “peers”
–All communication occurs on the same network
segment

5. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 5
Nonroutable Protocols (continued)

6. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 6
Nonroutable Protocols (continued)
•Several nonroutable protocolsexist in today’s
networking world
•NetBEUI (NetBIOS Enhanced User Interface)
–The most common nonroutable protocol
–Ships with all Microsoft Windows operating systems
•NetBEUI cannot scale into large internetworks
–Cannot hold Network layer information in its network
header

7. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 7
Routed Protocols
•Routed protocols
–Have packet headers that can contain Network layer
addresses
–Developed to support networks consisting of multiple
networks or subnetworks
•Protocols that can carry Network layer information
–Transmission Control Protocol/Internet Protocol
(TCP/IP)
–Internetwork Packet Exchange/Sequenced Packet
Exchange (IPX/SPX)

8. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 8

9. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 9
Routed Protocols (continued)
•For routed protocols to work on a network
–Every device must be configured with a unique IP or
IPX address (logical address)

10. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 10

11. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 11
Routing Protocols
•Routing protocols
–Protocols used by routers to make path determination
choices and to share those choices with other routers
•Hop count
–The number of routers a packet must pass through to
reach a particular network
•Metric
–A value used to define the suitability of a particular
route
–Routers use metrics to determine which routes are
better than other routes

12. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 12
Routing Protocols (continued)

13. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 13
Routing Protocols (continued)
•Autonomous system (AS)
–Uses Interior Gateway Protocols as routing protocols
–A group of routers under the control of a single
administration
•Interior Gateway Protocols (IGPs)are
–Routing protocols used within an AS
•Exterior Gateway Protocols (EGPs)
–Routing protocols used to route information between
multiple autonomous systems

14. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 14
Routing Protocols (continued)

15. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 15
Routing Protocols (continued)
•Examples of IGPs
–Routing Information Protocol (RIP)
–Interior Gateway Routing Protocol (IGRP)
–Enhanced Interior Gateway Routing Protocol
(EIGRP)
–Open Shortest Path First (OSPF)
•Example of EGP
–Border Gateway Protocol (BGP)

16. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 16
Two Types of IGPs
•Distance-vector routing protocols
–Broadcast their entire routing table to each neighbor
router at predetermined intervals
–The actual interval depends on the distance-vector
routing protocol in use
•Varies between 30 and 90 seconds
–Sometimes referred to as routing by rumor
–Suffer from slow time to convergence
•A state where all routers on the internetwork share a
common view of the internetwork routes

17. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 17
Two Types of IGPs (continued)

18. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 18
Two Types of IGPs (continued)

19. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 19
Two Types of IGPs (continued)
•Distance-vector routing protocols (continued)
–Routing loops
•Often referred to as count-to-infinity problems
•Loops, without preventive measures, will cause packets
to bounce around the internetwork infinitely
–Defining a maximum
•One of the easiest ways to limit count-to-infinity
problems
–Split horizonand split horizon with poison reverse
•Two other common ways to prevent routing loops when
using distance-vector routing protocols

20. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 20

21. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 21
Two Types of IGPs (continued)
•Distance-vector routing protocols (continued)
–Hold-down timer
•Another common technique used to stop routing loops
•Allow a router to place a route in a state where it will
not accept any changes to that route
•Link-state routing protocols
–Use link-state advertisements (LSAs)to inform
neighbor routers on the internetwork
–LSAs contain only the local links for the advertised
router

22. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 22
Two Types of IGPs (continued)
•Link-state routing protocols (continued)
–Shortest Path First (SPF) algorithm
•Uses the link information to compute the routes
•Router CPU resources are used instead of bandwidth
–Link-state packets (LSPs)
•Packets used to send out LSAs
•Allow every router in the internetwork to share a
common view of the topologyof the internetwork
–A link-state routing protocol floods, or multicasts,
LSPs to the network
–Later updates will be triggered updates

23. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 23

24. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 24
Two Types of IGPs (continued)
•Link-state routing protocols (continued)
–Routers using link-state protocols must be configured
with more memory and processing power
•Than those using distance-vector routing protocols
–Link-state routing protocols such as OSPF are much
more complicated to configure on the routers

25. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 25
Two Types of IGPs (continued)

26. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 26
Routing Information Protocol
•Routing Information Protocol (RIP)
–The easiest Interior Gateway Protocol to configure is
RIPv1
–A distance-vector routing protocol that broadcasts
entire routing tables to neighbors every 30 seconds
–RIP uses hop count as its sole metric
•RIP has a maximum hop count of 15
–As a result, RIP does not work in large internetworks
•RIP is capable of load balancing
•RIP is susceptible to all the problems normally
associated with distance-vector routing protocols

27. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 27
Enabling RIP Routing

28. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 28
Enabling RIP Routing (continued)
•To start configuring RIP, you must:
–Enter privileged mode first
–Enter global configuration mode on your router
•Enable RIP with the router ripcommand

29. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 29
Enabling RIP Routing (continued)

30. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 30
Enabling RIP Routing (continued)

31. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 31
Configuring RIP Routing for Each
Major Network
•networkcommand
–Turns on RIP routing for a network
–An individual networkcommand must be issued for
each separate network directly connected to the router
•show ip routecommand
–Displays a router’s routing table
•Administrative distance
–A value used to determine the reliability of the
information regarding a particular route
–Administrative distances range from 0–255

32. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 32
Configuring RIP Routing for Each
Major Network (continued)

33. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 33
Configuring RIP Routing for Each
Major Network (continued)

34. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 34
Show ip protocoland debug ip
ripCommands
•Commands used to monitor RIP
•A route is considered invalid if six consecutive
update intervals pass without an update from that
route
•Flush interval
–The time at which a route will be totally removed from
the routing table if no updates are received
•debug ip ripcommand
–Displays real-time rip updates being sent and received
and places very high processing demands on your
router, which could affect network performance

35. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 35
Show ip protocoland debug ip
ripCommands (continued)

36. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 36

37. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 37
Show ip protocoland debug ip
ripCommands (continued)

38. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 38
Show ip protocoland debug ip
ripCommands (continued)

39. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 39
Show ip protocoland debug ip
ripCommands (continued)

40. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 40
Interior Gateway Routing Protocol
•IGRP is a proprietary distance-vector routing
protocol
–Created by Cisco to solve some of the problems
associated with RIP
•A larger hop-count metric allows IGRP to be used on
larger networks
–IGRP supports a hop count of 255, although 100 is the
default if hop count is configured to be used as a
metric
•The metric maximum-hopscommand allows you
to set the maximum hop count for IGRP

41. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 41
Interior Gateway Routing Protocol
(continued)
•The default metrics for IGRP are bandwidth and
delay only
•Metrics that can be configured for IGRP
–Hops: number of routers between source and
destination networks
–Load: the load on a link in the path
–Bandwidth: the speed of the link (default)
–Reliability: measures reliability with a scale of 0 to 255
–Delay: the delay on the medium (default)
–MTU: the size of the datagram

42. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 42
Static Routing
•Some networks are so small that using a routing
protocol creates:
–Unnecessary traffic
–An inefficient use of router processor resources
•Stub routers
–Routers with only one route out
–Stub routers are usually the last router in a chain
•Stub networks
–Networks with one route to the Internet
•Static routesare configured by a network
administrator using the ip routecommand

43. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 43
Adding Static Routes

44. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 44
Adding Static Routes (continued)
•Syntax for the ip routecommand:
ip route [destination network address]
[destination network mask] [ip address
next hop interface] [administrative
distance]
•Examples:
ip route 172.32.3.0 255.255.255.0
172.32.2.2
ip route 172.32.4.0 255.255.255.0
172.32.2.2

45. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 45
Adding Static Routes (continued)
•Changing administrative distance
–The ip routecommand allows you to configure an
administrative distance
–Unless you add an administrative distance value to the
end of your ip routecommand
•The administrative distance will be 1
•Configuring a default route
–All packets that are not defined specifically in your
routing table will go to the specified interface for the
default route

46. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 46
Adding Static Routes (continued)
•Configuring a default route (continued)
–A default routeis a type of static route that the
administrator configures
–You can use the ip default-networkcommand or
the ip route 0.0.0.0 0.0.0.0 command to
configure a default route
–Default routes are sometimes called quad zero
routes
–A default route is used only if no other route to a
network exists in the routing table

47. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 47
Adding Static Routes (continued)

48. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 48
Summary
•Some protocols are designed to be used in small
networks without the need for Network layer
addressing
•The most common nonroutable protocol is
NetBEUI
•Other protocols were designed with the ability to
move between multiple networks via Network layer
addressing
•The most common routed protocol suite is TCP/IP

49. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 49
Summary (continued)
•Protocols must be available that can find the best
path throughout an internetwork and relay that
information to routers
•Routing protocols are classed in two major groups:
Interior Gateway Protocols and Exterior Gateway
Protocols
•Interior routing protocols are further divided into
distance-vector and link-state routing protocols
•These two types of Interior Gateway Protocols use
very different methods to determine the best path
in an internetwork

50. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 50
Summary (continued)
•Distance-vector protocols periodically broadcast
entire routing tables to neighbor routers
•Link-state protocols multicast link updates to
routers in their area upon startup and when
network topology changes
•Two common distance-vector IGPs discussed in
this chapter are the Routing Information Protocol
and the Interior Gateway Routing Protocol
•Static routes are used to conserve bandwidth and
lower memory and CPU load on a router while still
allowing for correct routing table creation