Transcript Chapter 12 - YSU Computer Science & Information Systems

Cisco Systems Networking
Academy
S2 C 12
Routing Protocols
Setup Mode
• Initial Configuration
– No valid startup-config
– System load ends with setup mode
– Use system configuration dialogue to setup
• Result is minimal-feature router configuration
• Can configure later to add protocol and interface changes
– Minimal contains inventory of interfaces, opportunity to enter
global parameters, opportunity to enter interface parameters,
setup script, opportunity to accept configuration
» Whey you answer YES, it becomes running configuration
» Configure allows you to enter additional commands
Initial Setup
• Each interface must be configures with an IP
address and a mask
– Set static routes
• Point-to-point
• Stub networks
– Set Default routes
• No router table entry for destination network
– Set Dynamic routes
• Router learns paths by receiving period updates from other
routers
IP Route Command
• Requires
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Network
Mask
Address
Interface
– Distance
destination network
subnet mask
IP address of next-hop router
name of interface to use to get to
destination network
Administrative distance – value
to help determine best path- low
is good (trustworthiness 0-255)
Using IP Route Command
• IP route 172.11.1.0 255.255.255.0 172.11.2.1
– Specifies static route to subnet
– Subnet mask in effect
– IP address of next-hop router in path to destination
• LAB
– Configure a static route between neighboring routers
Default Network
• Router (config)# ip default-network
172.22.22.1
– Configures default network
• Requires additional command
– Redistribute static
• S0 all networks have knowledge of the candidate
default network
Sample Commands
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Router (config)# router rip
Router (config)# network 145.45.3.0
Router (config)# network 191.23.21.0
Router (config)# default-network 154.44.1.0
Autonomous System
• A routing protocol such as Cisco's IGRP
requires that you specify this unique,
assigned autonomous system number in
your configuration.
• The Network Information Center (NIC)
assigns a unique autonomous system to
enterprises.
Autonomous Systems
• Interior Routing Protocols
– Used within autonomous system
• RIP, IGRP, EIGRP, OSPF
• Exterior Routing Protocols
– Used between autonomous systems
• BGP (Border Gateway Protocol)
• EGP (Exterior Gateway Protocol)
Global Configuration
• Select routing protocol (s)
• Specify network (s)
– Router(config)# router rip
• An option could be autonomous number
– Router(config-router)# 172.34.3.0
• Specifies a directly connected router
• Interface Configuration
– Verify address/subnet mask
RIP
• Specified in RFC 1058
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Distance vector
Hop count is metric
Max is 15; over 15 will discard packet
Routing updates broadcast every 30 seconds
• In RIP all subnet masks must be the same. RIP does
not share subnetting information in routing updates.
Show IP Protocol
• Displays values, about routing timers and
network information, that are associated
with the entire router
– Shows protocol, how often updated, next
update due time, hold down, routing for all
networks, gateways, distances and last update
– Administrative distance – default 120
Show IP Route
• Lets you examine the contents of the
routing table
• Essential (for troubleshooting why the
router may be dropping or incorrectly
routing packets
• Contains entries for all known networks and
subnetworks with a code that shows how
information was learned
IGRP
• Distance-vector router protocol – Cisco
• Sends updates every 90 seconds
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Handles indefinite, complex topologies
Flexible for different bandwidth & delay
Scalable for functioning in large networks
Composite metric
• Bandwidth, delay, load, reliability
• Speed is primary consideration
Enable IGRP
• Router (config) # router igrp autonomoussystem
• Selects IGRP as routing protocol
• Router (config-router)# network network #
• Identifies connected network
• Like RIP, all subnet masks must be the same
– does not share subnetting information in
routing updates
Sample Commands
• Router (config) # router igrp 109
– Selects igrp as routing protocol for network 109
• Router (config-router)# network 1.0.0.0
– Specifies directly connected networks
Show IP Protocol
• Router # show ip protocol
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Identifies protocol
Show algorithm used to calculate metric
Shows update period and next due update
Shows hold down period
Shows networks routed
Shows routing information source
Show ip interface
Router > show ip interface
Displays status and global parameters
associated with all IP interfaces
Cisco IOS enters route in routing table if
interface can send and receive – marked up
Unusable interfaces are removed from table
Display from show ip interface
Internet Address and subnet mask & broadcast
address
Access lists if any
Security level
Split horizon (enabled) or not
Other features enables or disabled
Show IP Route
• Examine contents of routing table
• Troubleshoot why packets are dropped or
incorrectly routed
• Tables contains all known networks and
subnets and metrics
• Shows how information was learned
• Shows if network is connected
Debug ip rip
• Powerful but bandwidth intensive
• Allow real time examination of routing updates
• Displays routing updates as they are sent and
received
• Can decrease network performance and cause loss
or connectivity – use only during times of low
network usage
• No debug ip rip
• No debug all
Lab
• Use Cisco commands learned to date
– Loops
• Hold-down timers, max hop count, counting to
infinity, poison reserve and split horizon
– DCE connection
– Interfaces
• Configure entire 5-router network
• Troubleshoot problems