Cisco networking, CNET-448 Chapter Introduction Cisco networking, CNET-448 Chapter 3 Enhanced Interior Gateway Routing Protocol (EIGRP) Prepared by: Sikandar Shah

Objectives IP Routing Technologies covered in this chapter are, Chapter Objectives Objectives IP Routing Technologies covered in this chapter are, 2.0 Routing Technologies 2.2 Compare and contrast distance vector and link-state routing protocols 2.3 Compare and contrast interior and exterior routing protocols 2.6 Configure, verify, and troubleshoot EIGRP for IPv4 2.7 Configure, verify, and troubleshoot EIGRP for IPv6

IP ROUTING EIGRP EIGRP is a classless, distance-vector protocol that uses the concept of an autonomous system. Support for IP and IPv6 via protocol dependent modules. Considered classless (same as RIPv2 and OSPF) Support for VLSM/CIDR Support for summaries and discontiguous networks Efficient neighbor discovery Communication via Reliable Transport Protocol (RTP) Best path selection via Diffusing Update Algorithm (DUAL) Reduced bandwidth usage with bounded updates No broadcasts

IP ROUTING Neighbor Discovery Before exchanging routes with each other, EIGRP routers need to become neighbors, and following conditions are checked first. Hello or ACK received: AS numbers match: Identical metrics (K values):

EIGRP Metrics Network Troubleshooting Bandwidth K1=1 Load K2 =0 Delay K3=1 Reliability K4=0 MTU K5=0 Metric= [K1*bandwidth+(K2xBandwidth)/(256- load)+K3xDelay]x[K5/(Reliability+k4)] Metric=((107/lowest bandwidth) + sum of all delays)*256 R1# show ip protocols, command used to see the K values

Advertised Distance Reported/advertised distance (AD) EIGRP TERMINOLOGY Advertised Distance Reported/advertised distance (AD) This is the metric of a remote network, as reported by a neighbor. It’s also the routing table metric of the neighbor and is the same as the second number in parentheses as displayed in the topology table. In the figure, routers SF and NY are both advertising the path to network 10.0.0.0 to the Corp router, but the cost through SF to network 10.0.0.0 is less than NY.

EIGRP TERMINOLOGY Feasible Distance This is the best metric among all paths to a remote network, including the metric to the neighbor that’s advertising the remote network. The route with the lowest FD is the route found in the routing table. The metric of a feasible distance is calculated using the metric reported by the neighbor that’s referred to as the reported or advertised distance plus the metric to the neighbor reporting the route. D 10.0.0.0/8 [90/2195456] via 172.16.10.2, 00:27:06,Serial0/0 The entire cost for this router to get to network 10.0.0.0.

Successor & Feasible Successor EIGRP TERMINOLOGY Successor & Feasible Successor Successor: It is the best route to a remote network. A successor route is the lowest cost to a destination and placed in the routing table. The topology table contains both successor and feasible successor routes. Feasible Successor(FS): A FS is defined as a path whose advertised distance is less than the feasible distance of the current successor and considered a backup route.

EIGRP ROUTING EIGRP tables Types

IP ROUTING EIGRP tables Types 1. Neighbor table: Contains information about the specific routers with whom neighbor relationship have been formed. Neighbor address and interface are recorded in neighbor table, it is stored in RAM. Sequence numbers are used to match acknowledgments with update packets. 2. Topology table: Used by Diffusing Update Algorithm (DUAL) to calculate the best loop-free path to each remote network. All routes in the AS are stored in the topology table. 3. Routing Table: EIGRP populates its routing table from topology table, best routes are selected for placement into routing table. Anything found in the routing table is considered a successor route.

Discontiguous networks IP ROUTING Discontiguous networks

Reliable Transport Protocol (RTP) IP ROUTING Reliable Transport Protocol (RTP) EIGRP depends on RTP to manage the communication of messages between EIGRP-speaking routers. EIGRP sends multicast traffic using Class D address 224.0.0.10 to its known neighbors. If a router doesn’t get a reply from a neighbor via the multicast, EIGRP will then try using unicasts to resend the same data. After 16 unicast attempts the neighbor will then be declared dead.

EIGRP EIGRP Packets Types Update: An update packet contains route information. Updates are sent either as multicast or unicast. Updates are always reliable. Query: It is a request for specific routes and always uses the reliable multicast method. Reply: It is sent in response to a query via unicast method. Hello: A Hello packet is used to discover EIGRP neighbors and is sent periodically via unreliable multicast. ACK: Sent in response to an update and is always sent as unreliable unicast.

Load Balancing <1-32> Number of paths Network Troubleshooting Load Balancing EIGRP can provide equal-cost load balancing across up to 4 links, maximum limit is 32 links with IOS 15.0. R1(config)#router eigrp 10 R1(config-router)# maximum-paths 8 <1-32> Number of paths Maximum hop count for EIGRP is 255, default is 100. R1(config-router)#metric maximum-hops ? <1-255> Hop count R1#show ip protocols variance 1 shows equal-cost load balancing.

Network Troubleshooting Split Horizon It means that if a route update is received on an interface from a neighbor router, this interface will not advertise those networks back out to the neighbor router who sent them. R#show ip interface serial0/0/0

Troubleshooting scenario EIGRP Troubleshooting Troubleshooting scenario Troubleshooting steps: Interfaces between the devices are down. The two routers have mismatching EIGRP autonomous system numbers. Proper interfaces are not enabled for the EIGRP process. An interface is configured as passive. The K values are mismatched EIGRP authentication is misconfigured Also, if the adjacency is up, but you’re not receiving remote network updates, there may be a routing problem, likely caused by these issues: The proper networks aren’t being advertised under the EIGRP process. An access list is blocking the advertisements from remote networks. Automatic summary is enabled

Verifying & Troubleshooting EIGRP EIGRP Troubleshooting Verifying & Troubleshooting EIGRP

EIGRP IPV6 EIGRPv6 Hello packets are sent using multicast address of FF02::A(A=10). EIGRPv6 is enable from the interface configuration mode. Routing process need to be enabled like an interface with the no shutdown command. Corp(config)#ipv6 unicast-routing Corp(config)#ipv6 router eigrp 10 Corp(config-rtr)#no shutdown Corp(config-if)#ipv6 eigrp 10

Written Labs and Review Questions Further Study Written Labs and Review Questions Read through the Exam Essentials section together in class Open your books and go through all the written labs and the review questions. Review the answers in class.