Transcript Chap 12 Routing Protocols

Chap 12
Routing Protocols
Andres, Wen-Yuan Liao
Department of Computer Science and Engineering
De Lin Institute of Technology
[email protected]
http://www.cse.dlit.edu.tw/~andres
Initial Router Configuration
Setup mode
Initial IP routing table
How a router learns about
destinations
ip route
ip default-network
Setup mode
The router is unable to
locate a valid startup-config
file
Sufficient, but minimalfeature, router configuration
Initial IP routing table
Initially, a router must refer to
entries about networks or
subnets that are directly
connected to it
Each interface must be
configured with an IP address
and a mask
Learns about destinations
Static routes
Manually defined by the
system administrator as the
next hop to a destination
Useful for security and
traffic reduction
Learns about destinations
Default routes
Manually defined by the
system administrator as the
path to take when there is
no known route to the
destination
Learns about destinations
Dynamic routing
The router learns of
paths to destinations by
receiving periodic
updates from other
routers
ip route command
Static route
Manual configuration
Reflect some special
knowledge of the networking
situation
Routing updates are not sent
on a link
•The administrative distance: rating of
the trustworthiness (0 to 255)
•The higher the number, the lower the
trustworthiness rating
•Administrative distance : 1 is the
default
ip default-network
Keep routing tables shorter
When an entry for a
destination network does not
exist in a routing table, the
packet is sent to the default
network
Default route
Interior and Exterior
Routing Protocols
Autonomous system
Interior vs. exterior routing
protocols
Interior IP routing protocols
IP routing configuration tasks
Using the router and network
commands
Autonomous system
Consists of routers, run
by one or more operators
Network Information
Center (NIC):Dispatcher
16 bit number
Cisco's IGRP
IP routing configuration tasks
Global and interface parameters
Dynamic routing uses
broadcasts and multicasts to
communicate with other routers
The routing metric helps routers
find the best path
RIP
Key elements of RIP
Using router rip and network
commands to enable RIP
Enabling RIP on an IPaddressed network
Monitoring of IP packet flow
using the show ip protocol
command
Key elements of RIP
Distance-vector routing protocol
Hop count: metric
If the hop count is greater than
15, the packet will be discarded
By default, routing updates are
broadcast every 30 seconds
show ip protocol
Displays values, about
routing timers and network
information, that are
associated with the entire
router
Update routing table
information every 30 seconds
show ip route
Displays IP routing table
Contains entries for all known
networks and subnetworks,
along with a code that
indicates how that information
was learned
IGRP
Key characteristics of IGRP
router igrp & network commands
show ip protocol
show ip interfaces
show ip route
debug ip rip
Key characteristics of IGRP
Distance-vector routing protocol
Sends routing updates: 90 s
Versatility: handle indefinite,
complex topologies
Flexibility for segments with
different bandwidth and delay
Scalability: very large networks
Key characteristics of IGRP
Default two metrics: bandwidth
and delay
Metrics
Bandwidth
Delay
Load
Reliability
show ip protocol
Displays parameters, filters, and
network information about all of the
routing protocol(s)
K1-K5 metrics and the maximum
hop count
K1: bandwidth and K3: delay
K1= K3 = 1;K2 =K4 = K5 = 0
show ip interfaces
Displays the status
and global parameters
associated with all IP
interfaces
show ip route
Displays the contents of
an IP routing table
Information was derived
from IGRP (I), or from
direct connections (C)
debug ip rip
Displays RIP routing updates
as they are sent and received
Debug commands are
processor intensive
no debug ip rip or no debug all
Summary
Connected networks or subnets
Static/Default/Dynamic routes
ip route: static route
ip default-network: default route
RIP and IGRP