Cisco Networking Academy Chapter 6 Review Configuring EIGRP Otero Junior College

IGRP/EIGRP xSimilarities: share the same distance-vector routing technology use the same composite routing metric support all the same distance vectors, and their mathematical weights EIGRP also uses the IGRP variance feature to provide unequal-cost load balancing. xDifferences: There is only one minor difference in the algorithm that calculates the composite metric: The IGRP metric is 20 bits long, whereas the EIGRP metric is 32 bits long

IGRP/EIGRP Redistribution yIGRP doesn't have any concept of internal and external routes yEIGRP routes that are translated and redistributed into an IGRP network are treated as native IGRP routes. yAutomatic redistribution between IGRP and EIGRP will occur only if the two protocols are configured with the same autonomous system (AS) number xIf they have different AS numbers, they will assume that they are part of different networks

EIGRP yA Cisco proprietary routing protocol xFeatures: Rapid Convergence Efficient use of bandwidth Support for VLSM and CIDR Independence from Routed Protocols Multiple network-layer support

EIGRP Technologies yNeighbor discovery and recovery xEIGRP routers maintain routing tables by periodic communication to: Dynamically learn of new routers that join their network Identify routers that become either unreachable or inoperable Rediscover routers that had previously been unreachable xNeighbor discovery/recovery process consists of periodically transmitting a small hello packet to neighbors establishes the relationship between immediate neighbors (known as an adjacency) –used to exchange routing metrics supported and other information

EIGRP Technologies yReliable Transport Protocol (RTP) xused to transport all EIGRP message types through a network reliable packets require explicit acknowledgement –Update –Query –Reply unreliable packets do not require explicit acknowledgement –Hello –ACK (Cont.)

EIGRP Technologies yReliable Transport Protocol (RTP) xcan support both multicasting and unicasting Multicast packets are delivered to multiple, specific destinations simultaneously using a group address Unicast packets are explicitly addressed to a single destination can support both multicast and unicast transmissions simultaneously for different peers.

EIGRP Technologies yDiffusing Update Algorithm (DUAL) xFinite-state machine tracks all routes advertised by neighbors and uses the composite metric of each route to compare them selects loop-free path using a successor and remember any feasible successors –If successor lost - use feasible successor –If no feasible successor - query neighbors and recompute new successor

EIGRP Technologies yProtocol-specific modules xEIGRP can be easily retrofitted to support any new routed protocols that may be developed by just adding another protocol-specific module xEach protocol-specific module is responsible for all functions related to its specific routed protocol EXAMPLE The IP-EIGRP module is responsible for: –Sending and receiving EIGRP packets that bear IP data –Notifying DUAL of new IP routing information that is received –Maintaining the results of DUAL's routing decisions in the IP routing table –Redistributing routing information that was learned by other IP-capable routing protocols

EIGRP Neighbor Table yEach EIGRP router maintains a neighbor table that lists adjacent routers xthere is a neighbor table for each protocol that EIGRP supports xused to support reliable, sequenced delivery of packets One field in each row of the table is populated with the last sequence number of the packet received from that neighbor EIGRP uses this field for two purposes: –Sequence numbers are used to acknowledge specific packets that were delivered reliably –This field can also alert EIGRP to packets being received out of sequence.

EIGRP Neighbor Table yKey elements: xNeighbor address - the network-layer address of the neighbor router xQueue count - the number of packets waiting in queue to be sent if this value is constantly higher than zero, then there may be a congestion problem at the router a zero means that there are no EIGRP packets in the queue xSmooth Round Trip Timer (SRTT) - the average time it takes to send and receive packets from a neighbor used to determine the retransmit interval (RTO) xHold Time - the interval to wait without receiving anything from a neighbor before considering the link unavailable

EIGRP Routing Table yEIGRP chooses the best (successor) routes to a destination from the topology table and places these routes in the routing table xcontains the lowest-metric routes that DUAL calculated for all known destinations xcan contain up to six routes to each destination yA separate routing table is maintained for each routed protocol that EIGRP is configured to support.

EIGRP Topology Table yThe information needed to calculate a set of distances, and vectors, to all known and reachable destinations yEach EIGRP router maintains a topology table for each configured network protocol xEntries in a topology table can be either in an active or passive state A passive route is one that is stable and available for use An active route is one currently being recomputed. x A backup route (feasible successor) is retained can have multiple feasible successors for a destination

EIGRP Topology Table

EIGRP Route Tagging yEIGRP classifies routes as either internal or external xInternal routes are those that originated within an EIGRP network xExternal routes were either learned from a different routing protocol or are static routes that have been injected into EIGRP through redistribution External routes include the following information and are identified in the topology table –The identification number (router ID) of the EIGRP router that redistributed that route into the EIGRP network –The number of the Autonomous System where that route's destination resides –The protocol used in that external network –The cost or metric received from that external protocol –A tag that can be administratively set and used in route filtering

EIGRP Packet Types yHello Packets xused to discover (or rediscover) and track other EIGRP routers in the network xhello packets are transmitted at fixed intervals known as hello intervals default interval on relatively low-bandwidth (T1 or less) multipoint circuits (such as multipoint Frame Relay, ATM, and X.25 circuits) – 60 seconds default interval on higher-bandwidth interfaces including point-to-point serial links, multipoint circuits with bandwidth greater than T1, and LANs –5 seconds

EIGRP Packet Types yAcknowledgment Packets xused to acknowledge receipt of any EIGRP packet that requires reliable delivery xa hello packet without any data  sent as a unicast packet to a single, specific IP address

EIGRP Packet Types yUpdate Packets xused to convey routing information to known destinations Updates sent to a new neighbor provide a complete dump of topological data –update packets will be directly addressed to that neighbor Updates would be sent whenever a change in either topology or link metric occurred –update packets would use an IP multicast address to forward to multiple neighbors simultaneously xupdates contain only the information that has changed, when it has changed

EIGRP Packet Types yQuery Packets xused whenever a router needs specific information from one or all of its neighbors xonly sent when a destination becomes active  can be both unicast and multicast  Reply Packets xused to respond to a query xare unicast directly back to the originator of the query

Configuring EIGRP - IP yTo enable EIGRP and define the autonomous system xrouter(config)#router eigrp autonomous-system-number autonomous-system-number is the number that identifies the autonomous system used to indicate all routers that belong within the internetwork (value must match all routers within the internetwork) yTo indicate which networks are part of the EIGRP autonomous system on this router xrouter(config-router)#network network-number network-number is the network number that determines which interfaces of the router are participating in EIGRP and which networks are advertised by the router xThe network command configures only connected networks

Configuring EIGRP - IP yWhen using serial links, it is important to use the bandwidth on the interface to change the bandwidth used for calculating routing metrics xrouter(config-if)#bandwidth kilobit If you do not change the bandwidth for these interfaces, EIGRP assumes that the bandwidth on the link is of T1 speed If the link is slower, the router may not be able to converge, routing updates might become lost, or suboptimal path selection may result

Configuring EIGRP - IPX yTo enable IPX routing xrouter(config)#ipx routing yTo define EIGRP as the IPX routing protocol xrouter(config-ipx-router)#ipx router {eigrp autonomous-system-number | rip} If IPX EIGRP is selected, an autonomous system number must be specified (must be the same for all IPX EIGRP routers in the network) yIndicate which networks are part of the EIGRP autonomous system xrouter(config-router)#network network-number

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Show Commands - IPX

Cisco Networking Academy End Review Otero Junior College