EIGRP

EIGRP Topics EIGRP features EIGRP operation EIGRP metric EIGRP load balancing EIGRP configuration EIGRP route summarization EIGRP authentication

EIGRP Features Fast convergence Supports multiple protocols Granular metric Supports unequal costs load balancing Supports VLSM Flexible design/route summarization Supports authentication

EIGRP Features Loop free Incremental updates Sends to multicast Easy configuration

EIGRP Operation Advanced Distance Vector Forms neighbor relationships before exchanging routing information Maintains adjacency with hellos every 5 seconds on LAN; 3 missed and neighbor considered dead Neighbor information maintained in neighbor table Passive-interface command prevents forming any adjacencies out that interface

EIGRP Operation Updates Full upon first exchange Partial upon change in topology Bounded Reliably sent to 224.0.0.10 Acknowledged Contain subnet mask Summarizes at classful boundaries by default Manual summarization at interfaces

EIGRP Route Selection Metric calculated to destination is called Feasible Distance Neighbor through which best feasible distance is calculated is called successor Successor route or routes placed in routing table Routes through other neighbors may qualify as feasible successor Feasible successor routes maintained in topology table Falls back to feasible successor instead of re-computing route Diffusing Update Algorithm - DUAL

EIGRP Route Selection 150 B 45 55 120 192.168.1.0 A C E 45 180 D Purpose: The figure shows how the IGRP commands operate on the example network. Emphasize: An administrator only specifies directly connected networks that he wishes to publish to other routers. Without the network command, nothing is advertised. With a network command, the router will advertise every subnet within the Class A, B, or C network specified in the configuration. 45 180 D

EIGRP Composite Metric 19.2 kbps 19.2 kbps Source Destination Purpose: This figure presents the IGRP metric with its five possible components. Emphasize : Bandwidth and delay are the two metrics that are most commonly used. They also comprise the default metric. Note: Changing IGRP metrics can have great impact on network performance. Describe the IGRP 24-bit metric field: Bandwidth—Minimum bandwidth on the route in kilobits per second. Delay—Route delay in tens of microseconds. Reliability—Likelihood of successful packet transmission expressed as an integer from 0 to 255. Loading—Effective bandwidth of path. MTU—Minimum MTU in path, expressed in bytes. The following equation calculates the metric. It is presented for instructors and is not required to be taught. metric = [k1 * bandwidth + (k2 * bandwidth) / (256 - load) + k3 * delay] If k5 does not equal 0, an additional operation is done: metric = metric * (k5/(reliability + k4)) The default constant values are k1=k3=1 and k2=k4=k5=0. Again, if default values are set, metric = bandwidth + delay. The constants (k1, k2, k3) can be changed using the metric weights command. Changes to the IGRP constant values should be made with great care. Bandwidth Delay Reliability Loading MTU

EIGRP Load Balancing Maximum six paths – default 4 equal paths New Route Source Initial Route Purpose: The figure presents how IGRP load sharing improves throughput and increases reliability. Emphasize: Only feasible paths can be used for IGRP load sharing. Load-balancing methods vary according to the switching mode because the data structures for process switching, fast switching, and autonomous switching are all different. When process switching, the processor load balances packet by packet. When fast, autonomous, or silicon switching, load balancing is done destination by destination. By default, the amount of variance is set to one, which results in equal-cost load balancing. You can use the default-metric command to change the default metric. Transition: The following pages describe how to configure the IGRP routing protocol. Destination Maximum six paths – default 4 equal paths Next-hop router closer to destination Within metric variance – default is 1

EIGRP Load Balancing Router(config-router)#variance multiplier Control EIGRP load balancing Purpose: This figure displays the commands to allow load sharing and load balancing in an IGRP environment. Emphasize: Note the router configuration mode to the students.

Configuring EIGRP Router(config)#router eigrp autonomous-system Defines EIGRP as the IP routing protocol Purpose: This figure explains how to use the router igrp and network commands to configure an IGRP process. Emphasize: Note that the AS keyword is required for IGRP. You can use multiple network commands to specify all networks that are to participate in the IGRP process. Only those networks specified will be published to other routers. Router(config-router)#network network-number Selects participating attached networks

EIGRP Configuration Example Autonomous System = 100 E0 S2 S2 S3 S3 E0 172.16.1.0 192.168.1.0 A B C 172.16.1.1 10.1.1.1 10.1.1.2 10.2.2.2 10.2.2.3 192.168.1.1 router eigrp 100 network 172.16.0.0 network 10.0.0.0 router eigrp 100 network 192.168.1.0 network 10.0.0.0 Purpose: The figure shows how the IGRP commands operate on the example network. Emphasize: An administrator only specifies directly connected networks that he wishes to publish to other routers. Without the network command, nothing is advertised. With a network command, the router will advertise every subnet within the Class A, B, or C network specified in the configuration. router eigrp 100 network 10.0.0.0

Verifying the Routing Protocol—EIGRP S2 S2 S3 S3 E0 172.16.1.0 192.168.1.0 A B C 172.16.1.1 10.1.1.1 10.1.1.2 10.2.2.2 10.2.2.3 192.168.1.1 RouterA#sh ip protocols Routing Protocol is "iegrp 100" Outgoing update filter list for all interfaces is Incoming update filter list for all interfaces is Default networks flagged in outgoing updates Default networks accepted from incoming updates EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 EIGRP maximum hopcount 100 EIGRP maximum metric variance 1 Redistributing: eigrp 100 Routing for Networks: 10.0.0.0 172.16.0.0 Routing Information Sources: Gateway Distance Last Update 10.1.1.2 90 00:01:01 Distance: (default is 90) Purpose: This figure shows how the show ip protocol command is used to monitor IGRP operation. Emphasize: The command displays the routing protocols that are active on the router for IP. It also gives network and timer information. In this example, IGRP is displayed. Point out the timing information. Point out the list of networks for which the router is injecting routes. Point out the administrative distance metric.

EIGRP Show Commands show ip route eigrp show ip eigrp interfaces show ip eigrp neighbors show ip eigrp topology show ip eigrp traffic

Lab Lab files Lab scenarios EIGRP Configuration Lab-1.doc EIGRP Configuration Lab-1.pkt EIGRP Configuration Lab-2.pkt