Lecture #4 EIGRP Asst.Prof. Dr.Anan Phonphoem Department of Computer Engineering, Faculty of Engineering, Kasetsart University, Bangkok, Thailand

EIGRP “Enhanced” Interior Gateway Routing Protocol Cisco proprietary, released in 1994 advanced distance-vector EIGRP is an advanced distance-vector routing protocol that relies on features commonly associated with link-state protocols. hybrid routing protocol Sometimes called a hybrid routing protocol It is not a link-state Same disadvantages as distance-vector

EIGRP Improved version of IGRP Backwards compatible with IGRP Improved convergence Sends updates like a link state routing protocol Supports VLSM/CIDR Supports many layer 3 routed protocols (not just IP)

Comparison IGRPEIGRP Classful Routing ProtocolClassless Routing Protocol VLSM, CIDR bandwidth = (10,000,000/bandwidth kbps) delay = delay/10 24 bit metric for bandwidth and delay bandwidth = (10,000,000/bandwidth kbps) * 256 delay = (delay/10) * bit metric for bandwidth and delay Maximum Hop Count = 255Maximum Hop Count = 224 No differentiation between internal and external routes. Outside routes (redistributed) are tagged as external routes. Automatic redistribution between IGRP and EIGRP as long as “AS” numbers are the same.

Metric Calculation EIGRP

Displaying Interface Values shows reliability as a fraction of 255, for example (higher is better): rely 190/255 (or 74% reliability) rely 234/255 (or 92% reliability) rely 255/255 (or 100% reliability) Router> show interface s0/0 Serial0/0 is up, line protocol is up Hardware is QUICC Serial Description: Out to VERIO Internet address is /30 MTU 1500 bytes, BW 1544 Kbit, DLY usec, rely 255/255, load 246/255 Encapsulation PPP, loopback not set Keepalive set (10 sec) BandwidthDelay ReliabilityLoad shows load as a fraction of 255, for example (lower is better): load 10/255 (or 3% loaded link) load 40/255 (or 16% loaded link) load 255/255 (or 100% loaded link)

Displaying Interface Values Router> show interface s0/0 Serial0/0 is up, line protocol is up Hardware is QUICC Serial Description: Out to VERIO Internet address is /30 MTU 1500 bytes, BW 1544 Kbit, DLY usec, rely 255/255, load 246/255 Encapsulation PPP, loopback not set Keepalive set (10 sec) BandwidthDelay ReliabilityLoad Routing Table Metric Default: Slowest of bandwidth plus the sum of the delays of all outgoing interfaces from “this router” to the destination network.

EIGRP Metrics Values displayed in show interface commands and sent in routing updates. Calculated values (cumulative) displayed in routing table (show ip route).

Routing Table SanJose2#show ip route D /24 [90/ ] via , 00:28:26, Serial0

How doe SanJose2 calculate the cost for this route ? Administrative Distance / Metric SanJose2#show ip route D /24 [90/ ] via , 00:28:26, Serial0

Displaying Interface Values Westasman> show interface fa0/0 Ethernet0 is up, line protocol is up Hardware is Lance, address is b3a.cf84 (bia b3a.cf84) MTU 1500 bytes, BW Kbit, DLY 100 usec, rely 255/255, load 1/255 SanJose2> show interface s0/0 Serial0/0 is up, line protocol is up Hardware is QUICC Serial Description: Out to Westasman Internet address is /30 MTU 1500 bytes, BW 1544 Kbit, DLY usec, rely 255/255, load 246/255

S0/ /30 S0/ /30 S0/ /30 S0/ /30 Fa0/ /24 Fa0/ /24 Fa0/ /24 EIGRP AS 100 Bandwidth = (10,000,000/bandwidth kbps) * 256 Westasman SanJose1 SanJose2 Bandwidth = 1,657,856 Bandwidth = 25,600 Delay = 512,000 Delay = 2,560 Determining the costs FastEthernet = (10,000,000/100,000) * 256 = 25,600 T1 = (10,000,000/1544) * 256 = 1,657,856

S0/ /30 S0/ /30 S0/ /30 S0/ /30 Fa0/ /24 Fa0/ /24 Fa0/ /24 EIGRP AS 100 Delay = (delay/10) * 256 Westasman SanJose1 SanJose2 Bandwidth = 1,657,856 Bandwidth = 25,600 Delay = 512,000 Delay = 2,560 Determining the costs FastEthernet = (100/10) * 256 = 2,560 T1 = (20,000/10) * 256 = 512,000

S0/ /30 S0/ /30 S0/ /30 S0/ /30 Fa0/ /24 Fa0/ /24 Fa0/ /24 EIGRP AS 100 What is the cost (metric) for /24 from SanJose2? Westasman SanJose1 SanJose2 Bandwidth = 1,657,856 Bandwidth = 25,600 Slowest! Delay = 512,000 Delay = 2,560 1,657, ,000 2, ,172,416 Cost: Slowest bandwidth + sum of delays The cost! Determining the costs bandwidth = (10,000,000/bandwidth kbps) * 256 delay = (delay/10) * 256

The Routing Table Administrative Distance / Metric SanJose2#show ip route D /24 [90/ ] via , 00:28:26, Serial0

EIGRP and IGRP compatibility Automatic redistribution occurs when the same AS number is used for EIGRP and IGRP. EIGRP scales the IGRP metric by a factor of 256. IGRP reduces the metric by a factor o 256.

EIGRP and IGRP compatibility EIGRP will tag routes learned from IGRP, or any outside source, as external because they did not originate from EIGRP routers. IGRP cannot differentiate between internal and external routes. 10,476 = 6,476(BW)+2,000(DLY)+2,000(DLY) IGRP Metrics! (Does not multiply by 256. External

Features Hellos sent every 5 sec. Neighbour table Topology table DUAL takes information in neighbour & topology table and calculates best routes (‘successors’) and adds them to the Routing Table ‘Feasible successors’ are alternative, backup routes

Technology Hellos multicast every 5 seconds to Holdtime (route dead) - 3 x hello interval RTP used as a reliable transport protocol to remain protocol independent Sequence numbers used on replies/acknowledgements to hellos – unicast NOT multicast Multicast update packets sent when topology changes

Configuration router(config)#router eigrp autonomous-system-number router(config-router)#network network-number router(config-if)#bandwidth kilobits router(config-if)#eigrp log-neighbor-changes EXAMPLE router(config)#router eigrp router(config-router)#network router(config-router)#network router(config-if)#bandwidth 64 router(config-if)#eigrp log-neighbor-changes

Route Summarization EIGRP automatically summarises routes Sub network address /24 would be advertised as /16 To turn off auto-summarisation Router(config-router)#no auto-summary Router(config-if)#ip summary-address eigrp

Verification show ip eigrp neighbors show ip eigrp interfaces show ip eigrp topology show ip eigrp traffic debug eigrp fsm debug eigrp packet

Reference Cisco Curriculum Rick Graziani, Cabrillo College