Download Advanced Networking Concepts & Troubleshooting

CCNA: Cisco Certified
Network Associate Study
Guide
CHAPTER 5:
IP Routing
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The CCNA exam topics covered in this
chapter include the following:
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What is Routing?
To route a router need to know:
– Remote Networks
– Neighbor Routers
– All Possible routes to remote network
– The absolute best route to all remote networks
– Maintain and verify the routing information
D
C
B
A
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Basic Path Selection
What interface will the router send out a packet if
it has destination address of 10.10.10.18?
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Simple IP Routing
>ping 172.16.1.2
172.16.2.0
172.16.1.0
172.16.3.1 172.16.3.2
e0
e0
172.16.2.2
Host A
172.16.2.1
A
B
s0
s0
B
172.16.1.1
172.16.1.2
Host B
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Routing/PDU Example:
Host A Web browses to the HTTP
Server….
1. The destination address of a frame will be the _______________________
2. The destination IP address of a packet will be the IP address
of the ________________________________
3. The destination port number in a segment header will have a value of __
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Static Routes
Stub Network
172.16.1.0
172.16.2.0
SO
AA
172.16.3.1
SO
172.16.3.2
B
B
Routes must be unidirectional
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Static Route Configuration
ip route remote network
[mask]
{address|interface}
[distance]
[permanent]
Router(config)#ip route remote_network mask next_hop
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Static Route Example
Stub Network
172.16.2.0
172.16.1.0
SO
SO
A
172.16.3.1
172.16.3.2
B
B
ip route 172.16.1.0 255.255.255.0 172.16.3.2
or
ip route 172.16.1.0 255.255.255.0 s0
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Default Routes
Stub Network
172.16.1.0
172.16.2.0
SO
SO
A
172.16.3.1
172.16.3.2
B
B
ip route 0.0.0.0 0.0.0.0 172.16.3.1
ip classless
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Routing vs. Routed
• Routing protocols are used between routers to:
– Determine the path of a packet through a network
– Maintain routing tables
– Examples?
• Routed protocols are:
– Assigned to an interface
– Once the path is determined by the Routing protocol, determines
method of delivery
– Examples?
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Routing Protocols
IGPs: RIP, IGRP
Autonomous System 1
EGPs: BGP
Autonomous System 2
• An autonomous system is a collection of networks under a
common administrative domain.
• IGPs operate within an autonomous system.
• EGPs connect different autonomous systems.
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Classful Routing Overview
Classful routing protocols do not
include the subnet mask with the
route advertisement.
– Within the same network, consistency of the subnet
masks is assumed.
– Summary routes are exchanged between foreign
networks.
– Examples of classful routing protocols:
• RIP Version 1 (RIPv1)
• IGRP
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Classless Routing Overview
Classless routing protocols include the
subnet mask with the route
advertisement.
– Classless routing protocols support variable-length
subnet masking (VLSM).
– Summary routes can be manually controlled within the
network.
– Examples of classless routing protocols:
•
•
•
•
RIP Version 2 (RIPv2)
EIGRP
OSPF
IS-IS
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Administrative Distance
Router B
Router A
RIP
Administrative
Distance=120
IGRP
Administrative
Distance=100
Router C
Router D
Default Administrative Distance
Directly Connected: 0
Static Route: 1
RIP: 120
IGRP: 100
EIGRP: 90
OSPF: 110
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Distance Vector
Distance—How far
Vector—In which direction
D
Routing
Table
C
B
A
Routing
Table
Routing
Table
Routing
Table
Distance vector algorithms do not allow a router to
know the exact topology of an internetwork.
All routers just broadcast their entire routing table out
all active interfaces on periodic time intervals
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Discovering Routes
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Discovering Routes
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Routing Loops
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Router Loops
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RIP Overview
64kbps
T1
T1
T1
–
–
–
–
Hop count metric selects the path, 16 is unreachable
Full route table broadcast every 30 seconds
Load balance maximum of 6 equal cost paths (default = 4)
RIPv2 supports VLSM and Discontiguous networks
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RIP Routing Configuration
Router(config)#router rip
Router(config-router)#network network-number*
10.3.5.0
192.168.10.0
172.16.10.0
router RIP
router RIP
network 172.16.0.0
network 10.0.0.0
network 172.16.0.0
network 192.168.10.0
*Network is a classful network address.
Every device on network uses the same subnet mask
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RIP Version 2
• Allows the use of variable length subnet masks
(VLSM) by sending subnet mask information
with each route update
• Distance Vector – same AD, and timers.
• Easy configuration, just add the command
“version 2” under the router rip configuration
router rip
network 10.0.0.0
version 2
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Discontiguous Addressing
• Two networks of the same classful networks are
separated by a different network address
192.168.10.0/24
192.168.10.0/24
10.1.1.0/24
– RIPv1 and IGRP do not advertise subnet masks, and therefore cannot
support discontiguous subnets.
– OSPF, EIGRP, and RIPv2 can advertise subnet masks, and therefore
can support discontiguous subnets.
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Passive Interface
Maybe you don’t want to send RIP updates
out your router interface connected to the
Internet. Use the passive-interface
command:
Router(config)#router rip
Router(config-router)#passive-interface serial0
Internet
X
S0
Updates
Gateway
This allows a router to receive route updates on an interface,
but not send updates via that interface
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Verifying RIP
Router#show ip protocols
Router#show protocols
Router#show ip route
Router#debug ip rip
Router#undebug all (un all)
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IGRP
• Interior Gateway Routing Protocol - Cisco Proprietary
• Uses bandwidth and delay of the line by default to select best path
Router A
Router B
Autonomous
System
Router C
Router D
Requires Autonomous System number for activation
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IGRP vs. RIP
• The important IGRP characteristics are
as follows:
–
–
–
–
More scalability than RIP
Fast response to network changes
Sophisticated metric
Multiple-path support
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Configuring IGRP
Router(config)#router igrp autonomous-system
Router(config-router)#network network-number*
10.3.5.0
router IGRP 10
network 172.16.0.0
network 10.0.0.0
192.168.10.0
172.16.10.0
router IGRP 10
network 172.16.0.0
network 192.168.10.0
*Network is a classful network address.
Every device on network uses the same subnet mask
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Verifying IGRP
Router# show ip route
Router# show ip protocols
Router# debug ip igrp transaction
Router# debug ip igrp events
Router# undebug all (un all)
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