routing basics - (static-default-dynamic)

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1. 1
Lecture Objectives
•What is Static Routing?
–Configuring Static Routes
–Configuring Default Routes
•Comparison of Static and Dynamic Routing
•Dynamic Routing Characteristics
–Autonomous Systems Concepts
–Interior Routing Protocols vs. Exterior Routing Protocols
–Metric, Path Selection Criteria

2. 2
IP Routing Learns Destinations
•Three types of routes are there:
–Static routes
–Default routes
–Dynamic routing

3. 3
Static Routing

4. 4
Static Route Example
– This is a unidirectional route. You must have a route
configured in the opposite direction.
Stub Network
172.16.2.1
SO
172.16.1.0
B
172.16.2.2
Network
A B10.0.0.0
ip route 172.16.1.0 255.255.255.0 172.16.2.1
des-network mask Next Hop -IP

5. 5
Static Routes
Configure unidirectional static routes to and from a stub
network to allow communications to occur.
172.16.2.1
SO
172.16.1.0
B
172.16.2.2
Network
A B
Stub Network

6. 6
•Defines a path to an IP destination
network or subnet
ip route network [ mask ] { address | interface } [ distance ][ permanent ]
Router (config)#
Static Route Configuration

7. 7
255.255.255.0
172.16.2.0
Cisco A
172.16.1.0
172.16.2.1
Cisco B
E0
S0
S1
S2 S0
ip route 172.16.1.0 255.255.255.0 172.16.2.1
172.16.2.2
Static Route Example

8. 8
Figure: Network Design
Router R1
Router R2
B
A
E0
S0S1E0
200.100.100.0/24
1.0.0.0/8
200.150.100.0/24

9. 9
Figure: Network Design
Router R1
Router R2
B
A
E0
S0S1E0
200.100.100.0/24
1.0.0.0/8
200.150.100.0/24
C200.100.100.0/24
C1.0.0.0/8
C200.150.100.0/24
C1.0.0.0/8

10. 10
Figure: Network Design
Router R1
Router R2
B
A
E0
S0S1E0
200.100.100.0/24
1.0.0.0/8
200.150.100.0/24
C200.100.100.0/24
C1.0.0.0/8
S200.150.100.0/24
C200.150.100.0/24
C1.0.0.0/8
S200.100.100.0/24

11. 11
Default Route

12. 12
Default Routes
–This route allows the stub network to reach all known
networks beyond router A.
Stub Network
ip route 0.0.0.0 0.0.0.0 172.16.2.2
172.16.2.1
SO
172.16.1.0
B
172.16.2.2
Network
A B10.0.0.0
Message for destination network no bit checking next router IP

13. 13
Stub Network
•Stub Network
–A stub network is an internal network, usually a
LAN (Local Area Network) that carries data
packets only among local hosts. Data on a stub
network is destined for an endpoint located on
that network. Network traffic on a stub network
is local in that it doesn't travel off the internal
network.

14. 14
•Defines a default route
ip default-network network-number
Router(config)#
Default Route Configuration

15. 15
Company X
Public Network
Cisco A
Default Route Example
192.168.17.0
Cisco A Routing Table
ip default-network 192.168.17.0ip default-network 192.168.17.0
router rip
network 172.16.0.0
network 192.168.17.0
ip default-network 192.168.17.0

16. 16
Dynamic Routing

17. 17
Static and Dynamic Routing
•Static
–Static routing is a
form of routing in
which paths between
nodes are always used
in a pre-defined way.
–Uses a route that a
network administrator
enters into the router
manually
–Simple to design
–Cannot react to
network changes
automatically
•Dynamic
–Uses a route that a
network routing
protocol adjusts
automatically for
topology or traffic
changes
–Automatically react to
network changes
–Analyzes the incoming
routing updates

18. 18
Introduction to Routing Protocols
•Packets pass through many routers from
source to destination
•Dynamic nature of Internet; routes change
and need to be updated
•Routing protocol – combination of rules and
procedures allowing routers to inform one
another of changes

19. 19
Dynamic Routing Protocols
•Running a dynamic routing protocol will
allow our routers to share their network
information with each other and recover
from a network outage automatically.
•If an alternate path exists and all of the
routers are running properly configured
routing protocols, they will eventually locate
the alternate path and use it if the primary
path goes down.

20. 20
Networ
k
Protoco
l
Destinatio
n
Network
Connected
Learned
10.120.2.0
172.16.1.0
Exit
Interface
E0
S0
Routed Protocol: IP
Routers must learn destinations that are not
directly connected
172.16.1.010.120.2.0
E0
S0
What is Routing?

21. 21
What is a Routing Protocol?
•Routing protocols
are
used between
routers to
determine paths
and maintain
routing tables.
•Once the path is
determined a
router can route a
routed protocol.
Networ
k
Protoco
l
Destinatio
n
Network
Connecte
d
RIP
IGRP
10.120.2.
0
172.16.2.
0
172.17.3.
0
Exit
Interface
E0
S0
S1
Routed Protocol: IP Routing protocol: RIP,
IGRP
172.17.3.0
172.16.1.010.120.2.0
E0
S0
C
R
I

22. 22
•To route, a router needs to know:
–Destination addresses
–Sources it can learn from
–Possible routes
–Best route
–Maintain and verify routing information
What is Routing?
172.16.1.010.120.2.0

23. 23
Routing
•Routing:
–Selecting the best possible path to reach the
destination
–Occurs at layer 3
–It involves:
•Determining the optimal paths
•Transporting packets through a network, like
packet switching

24. 24
Planning the Configuration
•Network Protocols
–There are two major classes of network protocols
and we need both:
•Routed
–IP, IPX etc.
•Routing
–RIP, IGRP, OSPF, BGP etc.

25. 25
Routed and Routing Protocols
•Routed Protocols:
–Used for communication between routers and
computers e.g. IP etc.
–These are routed over an internetwork
•Routing Protocols:
–Used for communication between routers e.g.
RIP, IGRP, OSPF, BGP etc.
–These protocols implements routing algorithms

26. 26
Path Determination
•Metrics are used by routing protocols
–It is a standard of measurement, e.g. path
bandwidth, number of hops etc.
–Routing tables are maintained

27. 27
Routing Algorithms
•Design Goals
–Optimality
–Simplicity and low overhead
–Robustness and stability
–Rapid convergence
–Flexibility

28. 28
Routing Metrics
•Routing protocols uses different metrics to
select the best route
–Path Length
–Reliability
–Delay
–Bandwidth
–Load
–Communication Cost

29. 29
Autonomous Systems

30. 30
Autonomous System 100
Autonomous Systems
–An autonomous system is a collection of networks
under a common administrative domain
–IGPs operate within an autonomous system
–EGPs connect different autonomous systems
Autonomous System 200
IGPs: RIP, IGRP EGPs: BGP

31. 31
Interior Routing Protocols
•The routing protocols e.g. RIP, IGRP, OSPF, are
called interior routing protocols.
•They are meant to be run on routers under a common
administration I.e. within a single Autonomous
System

32. 32
•Routers under a common administration
Autonomous System

33. 33
Some Terminologies
•Hierarchical terminology of OSI
–End Systems (ES)
•Devices without packet forwarding capability
–Intermediate Systems (IS)
•Devices with packet forwarding capability
–Intradomain IS and Interdomain IS
•Autonomous Systems (AS)
–A system under the same administration, i.e.
where same protocol runs.
–Also called routing domains

34. 34
Interior vs. Exterior Protocols
•Interior Gateway Protocols (IGPs)
–Runs within an Autonomous System, e.g RIP,
IGRP
•Exterior Gateway Protocols (EGPs)
–Connects different Autonomous System, e.g.
BGP

35. 35
References
•TCP/IP Protocol Suite
–2
nd
Edition, Behrouz A. Forouzan, McGraw-Hill
Inc.
•Computer Networks
–4
th
Edition, Andrew S. Tananbaum
•Computer Networking; A Top Down
Approach Featuring the Internet
–3
rd
Edition: Jim Kurose and Keith Ross