Transcript IP Routing - courses.psu.edu

IST 228\Ch5\IP Routing
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IST 228\Ch5\IP Routing
Review of Chapter 4
• Start the router simulator. You will see the prompt "Router>". This
is the user mode prompt.
Change the name of the router to Router1.
• Set the enable password to “en123”.
• Set the secret password to “secret123”.
• Try the passwords.
• Set virtual terminal password to “vty123” for the virtual terminal 0-4
Router1#config terminal
Router1(config)#line vty 0 4
Router1(config-line)#login
Router1(config-line)#password vty123
Router1(config-line)#exit
• Set console 0 password to “con123”
Router1(config-line)#line console 0
• Now remove the passwords
Router1(config)#no enable password en123
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• Assign IP address for the Ethernet 0 interface.
• Assign IP address for the Serial 0 interface.
• Set the bandwidth of the Serial 0 interface to 56Kps.
Router1(config-if)#bandwidth 56
• Set the bandwidth of the Serial 0 interface to 56Kps.
Router1(config-if)#clock rate 56000
• Type “exit” to leave the serial interface and type “ctrl-z” to leave
configuration mode.
• Show the configuration of Ethernet 0, Serial 0
• Show the running configuration of Router1
Backing up your configuration to a TFTP server
Router1#copy running-config tftp
• Type “172.10.0.10” for the TFTP host.
• Type “Router1” to name the destination file.
Router1#copy tftp running-config
• Type “172.10.0.10” for the TFTP host.
• Type “Router1” for the configuration file name.
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IST 228\Ch5\IP Routing
IP Routing
• Nonroutable Protocols:
– All communication occur on the one local net segment
– Network source and destination infromation is not
needed.
– NetBEUI (NetBIOS Enhanced User Interface).
• Routed Protocols:
– Have packet headers with Network Layer address.
– TCP/IP, Internetwork Packet Exchange/Squence
Packet Exchange.
– Every device must configured with a unique IP or IPX
address.
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IP Routing
• Routers forward packets by looking the routing table and
discovering how to get remote networks.
• A configured router have only information about directly
connected networks.
– What happens a router receives a packet with a network not
listed in the routing table?
Routing table for RouterC
IST 228\Ch5\IP Routing
Different Types of Routing
• Static
• Default
• Dynamic
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Static Routing
•An administrator manually adds routes in each
router’s table.
•Benefits:
– No overhead on the router CPU
– No bandwidth usage between routers
– Security
•Disadvantages:
– It is not feasible in large networks
– Difficult to update
– Administrators must know networking very well
ip route [destination_network] [mask] [next-hop_address or
exit interface] [administrative_distance] [permanent]
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Setting a Static Routing Table
Establishing routes:
Router1# show ip route
:
Router1(config)# ip route 192.168.10.0 255.255.255.0
210.16.54.1
This command establishes an IP route to network 192.168.20
Add all other required routes in the routing table
Type “crtl-Z” to exit from configuration mode.
Check the status of the routing table using show ip route
Removing routes:
Router1(config)# no ip route 192.168.10.0
255.255.255.0 210.16.54.1
Verifying:
Router1# ping 192.168.10.50
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Default Routing
• Use to send packets with a remote destination
network not in the routing table to the next-hop
router.
• You can only use default routing on stub
networks-those with only one exit port out of the
network.
RouterA(config)#ip route 0.0.0.0 0.0.0.0 192.168.12.1
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Why use Default Routing?
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IST 228\Ch5\IP Routing
Dynamic Routing
• In dynamic routing, protocols are used to find and
update routing tables on routers.
• A routing protocol defines the set of rules used by a
router when communicating between neighbor routers.
– Routing Information Protocol (RIP)
– Interior Gateway Routing Protocol (IGRP)
– Enhanced Interior Gateway Routing Protocol (EIGRP)
• Types of routing protocols
– interior gateway protocols (IGPs)
• RIP, IGRP, EIGRP, OSPF
– exterior gateway protocols (EGPs)
• Border Gateway Protocol (BGP)
• Types of IGPs
– Distance Vector (RIP, IGRP)
– Link State (OSPF)
– Hybrid (EIGRP)
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Dynamic Routing Basics
• Hop count is the number of routers a
packet must pass through to reach a
particular network.
• An autonomous system (AS) is a group of
routers under the control of a single
administration, sharing the same routing
table information.
• Administrative Distance is used to rate
trustworthiness of routing information, 0
being the most trusted and the 255 least
trusted.
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Distance-Vector Routing Protocols
• Each router broadcasts its entire routing table to
neighbor routers at predetermined intervals (30
to 90 seconds).
• Called routing by rumor
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RIP Pinhole Congestion
• Two updates list the same remote network?
• Two updates list the same remote network and have the same AD?
• Two updates list the same remote network and have the same AD
and hop count?
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Router Convergence
Start Up
Converged
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Problems in Distance-Vector Routing
• It takes up CPU process and link bandwidth.
• If a network outage happens, slow converge of
distance-vector routing protocols can cause
inconsistent routing tables.
• routing loops (counting-to-infinity).
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Solutions
•
•
•
•
Maximum Hop Count
Split Horizon
Route positioning
Holddowns
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Routing Information Protocol (RIP)
• a true distance-vector protocol
• sends complete routing table out all interfaces
every 30 sec.
• uses only hop count to determine the best way.
• has maximum allowable hop count of 15
• is inefficient on large networks
• uses three different timers
– route update timer
– route invalid timer
– flush timer
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Setting up for Dynamic Routing
• Configure your interfaces (see the next page)
• Make sure that other routers in your network use the
same routing protocol (RIP or IGRP).
Lab_A(config)# router rip
Lab_A(config-router)#network 201.100.11.0
^Z
• Check your settings with show ip route
• Use ping to verify configuration and connectivity of the
network devices.
• You can use passive-interface serial 0 to stop
RIP updates from being propagated out serial interface 0,
but it can still receive RIP updates.
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Example for RIP configuration
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Interior Gateway Routing Protocol (IGRP)
• Cisco-proprietary distance-vector routing protocol
that can work only with Cisco routers.
• maximum hop count of 255 (100 default)
• can use bandwidth and delay of lines in order to
choose the best route.
• Timers to control the performance
–
–
–
–
update timers
invalid timers
holddown timers
flush
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Commands to verify your configuration
Commands
Meaning
show ip route
shows you the routing protocols configured on your router
and routing table
show protocols
displays all routed protocols and the interfaces on which
they are enabled.
show ip protocols
shows the routing protocols with all timing associated with
them
debug ip rip
displays routing updates in the console session as they are
sent and received.
debug ip igrp events
displays a summary of the IGRP routing information
running on the network
debug ip igrp transactions
displays the message request from neighbor routers
asking for updates.
undebug all
turns all debugging off
show running-config
shows the configuration currently running on the router
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Commands for configuration routing
Commands
Meaning
R(config)#router rip
Turns on RIP routing on a router
R(config)#router igrp [AS number]
Turns on IGRP routing on a router
R(config)#network [network IP]
Identifies networks that routing table will be
advertised by RIP and IGRP
R(config)#ip route [IP] [mask]
[interface IP]
Creates static and default routes on a router
R(config)#ip route [IP] [mask]
[interface IP]
Removes static and default routes
R(config)#ip classes
Tells a router to forward packets to a default
route when the destination network is not in
the routing table
IST 228\Ch5\IP Routing
Commands to configure dynamic
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