© 2002, Cisco Systems, Inc. All rights reserved.
© 2002, Cisco Systems, Inc. All rights reserved.
2
Enabling IGRP
Objectives
Upon completing this lesson, you will be able to:
Describe the features and operation of IGRP
Use Cisco IOS commands to configure dynamic routing using IGRP, given a functioning router
Use show and debug commands to identify anomalies in dynamic routing operation using IGRP, given an operational router
More scalable than RIP
Sophisticated metric
Multiple-path support
Introducing IGRP
Bandwidth
Delay
Reliability
Loading
MTU
IGRP Composite Metric
Maximum 6 paths (default = 4)
Within metric variance
Next-hop router closer to destination
IGRP Unequal Multiple Paths
Configuring IGRP
Router(config-router)#network network-number
Selects participating attached networks
Router(config)#router igrp autonomous-system
Defines IGRP as the IP routing protocol
Configuring IGRP (cont.)
Router(config-router)#traffic-share {balanced | min}
Controls how load-balanced traffic is distributed
Router(config-router)#variance multiplier
Controls IGRP load balancing
IGRP Configuration Example
Verifying the IGRP Configuration
Displaying the IP Routing Table
debug ip igrp transaction Command
debug ip igrp events Command
RouterA#debug ip igrp events
IGRP event debugging is on
RouterA#
00:23:44: IGRP: sending update to 255.255.255.255 via Ethernet0 (172.16.1.1)
00:23:44: IGRP: Update contains 0 interior, 2 system, and 0 exterior routes.
00:23:44: IGRP: Total routes in update: 2
00:23:44: IGRP: sending update to 255.255.255.255 via Serial2 (10.1.1.1)
00:23:45: IGRP: Update contains 0 interior, 1 system, and 0 exterior routes.
00:23:45: IGRP: Total routes in update: 1
00:23:48: IGRP: received update from 10.1.1.2 on Serial2
00:23:48: IGRP: Update contains 1 interior, 1 system, and 0 exterior routes.
00:23:48: IGRP: Total routes in update: 2
Updating Routing Information Example
Updating Routing Information Example (Cont.)
Updating Routing Information Example (Cont.)
Updating Routing Information Example (Cont.)
Summary
IGRP has several key features such as increased scalability, a sophisticated metric, and multiple paths.
IGRP uses a composite routing metric that can include bandwidth, delay, reliability, loading, and MTU value.
The IGRP composite routing metric supports multiple paths between source and destination.
Use the router igrp and network commands to create an IGRP routing process. Use the variance and traffic-share commands to configure IGRP load balancing.
Use the show ip protocols and show ip route commands to display information about your IGRP configuration.
Use the debug ip igrp transaction command to display transaction information on IGRP routing transactions and the debug ip igrp events command to display a summary of the IGRP routing information.