1. EIGRP

2. Table of Contents Basics of EIGRP Basics of EIGRP Configuration EIGRP Configuration Monitoring EIGRP Monitoring EIGRP Chapter 6 Lab Notes Chapter 6 Lab Notes EIGRP Terminology EIGRP Terminology EIGRP Operation EIGRP Operation

3. EIGRP Overview Enhanced version of Cisco’s proprietary IGRP dramatically increases operational efficiency because EIGRP… Uses a more granular version of IGRP’s metrics (32 bits v. 24 bits) Has faster convergence than any other IGP Is scalable because of VLSM and route summarization Supports multiple routed protocols through protocol-dependant modules Replaces Novell RIP and Apple’s RTMP Is technically an advance distance-vector routing protocol Uses partial updates Hello packets for neighbor discovery Is relatively easy to administer However, does not have OSPF’s hierarchical design (no areas)

4. EIGRP Metrics EIGRP scales IGRP’s metrics by a factor of 256 IGRP metric = 24 bits; EIGRP metric = 32 bits Bandwidth and Delay are equally weighted Reliability, Load, and MTU are off by default Hop count limited to 224 (IGRP’s limit is 255) To remember the metric components… Big = Bandwidth Dogs= Delay Really= Reliability Like= Load Me= MTU

5. EIGRP Tables Like OSPF, EIGRP maintains three unique tables to assist in routing traffic. Neighbor Table Topology Table Routing Table EIGRP maintains one table of each for each routed protocol configured on the router. For example, if a router was configured with IP, IPX and AppleTalk, EIGRP would maintain… 3 Neighbor Tables 3 Topology Tables 3 Routing Tables

6. Neighbor Table Use the show ip eigrp neighbors command to view the table. Similar to OSPF’s Adjacencies database; Contains a list of all neighbors discovered through hellos Maintains hello and holdtime intervals on each neighbor Maintains information required by RTP (discussed later) SRTT—Smooth Round-trip Timer; avg. time it takes to send and then receive a reply from that neighbor RTO—Retransmission Timeout; how long to wait without receiving an acknowledgement to a reliably sent packet Router#show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.224.2 Se0 13 00:01:28 930 5000 0 30 1 192.168.208.2 Se1 11 00:02:20 35 1140 0 21

7. Topology Table Use the show ip eigrp topology [all-links] command to view the table. Similar to OSPF’s Link-State (Topology) database; Contains all routes the router has learned about from its neighbors and all the information necessary to calculate a set of distances and vectors to all reachable destinations FD—Feasible Distance; lowest calculated metric to reach a destination as opposed to… RD—Reported Distance or Advertised Distance; distance to the destination reported by the neighbor. Router#show ip eigrp topology IP-EIGRP Topology Table for process 100 Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply, r – Reply status P 192.150.42.120 255.255.255.248, 1 successors, FD is 2172416 via 192.150.42.9 (2172416/2169856), Fddi0 P 192.150.42.8 255.255.255.248, 1 successors, FD is 28160 via Connected, Fddi0 Feasible Distance Reported Distance

8. Routing Table Use the show ip route command to view table Like all routing protocols, EIGRP maintains a routing table with… Best routes to destination networks Maintains up to four equal-cost routes for each destination Unequal-cost routes can be installed if the variance command has been configured You are already familiar with the routing table. You will notice that EIGRP routes are designated with a D.

9. EIGRP Concepts & Terminology Successor The best, least cost route to the destination installed in the routing table; multiple successors can be installed for load balancing Feasible Successor A next-hop alternative route to the destination kept in the topology table, ready to be installed if the successor fails; feasible successors are only in the topology table Active State During route recomputation, routes lost due to a successor’s failure are said to be in the active state. The active state ends when the route is restored or removed. Passive State Installed routes that are not in the process of being recomputed are said to be in the passive state.

10. EIGRP Concepts & Terminology Diffusing Update Algorithm (DUAL) EIGRP’s route computation engine; guarantees a loop-free topology; calculates EIGRP’s metric and installs successors in the routing table & feasible successors in the topology table Route Evaluation Occurs when the topology changes; DUAL evaluates the topology table, searching for feasible successors and immediately installing them, if found; no recomputation is necessary Route Recomputation DUAL begins recomputing if no feasible successors are found; queries neighbors for alternative routes; process ends when all neighbors have replied and DUAL either installs successor or removes route from the topology and routing tables. Protocol Dependant Modules (PDM) EIGRP’s scalable and adaptable feature because of its modularity; theoretically, EIGRP does not have to be completely rewritten to route IPv6—just add a PDM.

11. EIGRP Packet Types Hello Packets Unreliable multicast to 224.0.0.10 to discover and maintain neighbors; contains the router’s neighbor table Default hello interval depends on the bandwidth ≤ 1.544 Mbps = 60 sec. hello interval (180 holdtime) > 1.544 Mbps = 5 sec. hello interval (15 holdtime) Update Packets Sent reliably, there are 2 types Unicast to new neighbor discover; contains routing table Multicast to all neighbors when topology changes Query & Reply Packets Queries are multicast reliably during route recomputation, querying neighbors for a new successor to a lost route Neighbors unicast a reply to the query whether or not they have a route. Acknowledgement Packets “Dataless” packet that acknowledges the receipt of a packet sent reliably

12. Reliable Transport Protocol RTP is EIGRP’s flexible protocol used to transport message types through a network Since EIGRP is protocol independent, it has to have its own connection-oriented and connectionless services RTP allows unicasting and multicasting reliable and unreliable packets to peers simultaneously RTP maintains a transmission list in the neighbor table with sequence numbers to determine when a required acknowledgement has been received. Works much like TCP’s Positive Acknowledgement with Retransmission

13. EIGRP operation is completed in five stages: Building neighbor relationships Discovering routes Choosing the best routes Maintaining routes Removing routes These stages do not necessarily occur sequentially Building relationships and discovering routes occur together as do choosing and maintaining routers Note: The following EIGRP Operation discussion is adapted from CCNP Routing Exam Prep: Exam 640-503 (© 2000) by Robert Larson, et al. The EIGRP Process

14. Building Neighbor Relationships Neighbor relationships are established through the use of Hello packets A new router configured with EIGRP will multicast hello packets to directly connected routers The receiving routers will reply if the new router is… Configured with EIGRP In same AS Using the same metric weights EIGRP routers, unlike OSPF, do not have to have the same hello intervals Defaults, however, are 5 sec. for > T1 and 60 sec. for ≤ T1.

15. Discovering Routes While neighbor relationships are established, the following steps occur: The new router multicast hellos to 224.0.0.10 Directly connected routers respond with a unicast update packet containing all the routes in their routing table The new router replies to all neighbors with a unicast Ack packet and places the contents of the updates in its topology table The new router then unicast update packets to all neighbors with the contents of its topology table (this is how its neighbors learn about the router’s uniquely configured networks such as a new LAN) Neighbors reply to the new router’s update with an Ack packet.

16. Building/Discovering Example 1. C comes online and multicasts hellos to A & B. 2. A & B unicast an update packet containing routing table contents 3. C replies to unicast updates with Ack packet and builds topology table 4. C unicasts updates to A & B with contents of topology table (includes C’s new LAN) 5. A & B reply with an Ack packet. AB C

17. Choosing the Best Routes After a new router has received all the updates from directly connected neighbors, it can calculate its DUAL. First, the metric for each route in the topology table is calculated using the following formula: Metric = 256[(10,000,000/min. bandwidth) + sum of delays] Then, the route with the lowest cost is designated the successor and is installed (up to 4 with equal costs) in the routing table. DUAL then looks for feasible successors. A feasible successor must have a lower feasible distance to the destination than the installed route’s feasible distance. All feasible successors are maintained in the topology table so DUAL can install them immediately if the successor fails.

18. Maintaining Routes As new routers come online and old routes fail, EIGRP quickly and efficiently handles these situations with little or no downtime. As new routers come online, their hello packets and the ensuing update process has a “domino effect” on the network. All routers in the AS almost instantaneously converge on the router’s new networks. Maintaining routes also means informing directly connected neighbors when another neighbor stops sending hello packets at the required interval.

19. Removing Routes When a route fails (a directly connected neighbor is no longer sending hellos), the detecting router’s DUAL… Enters the route evaluation phase. Is there a feasible successor in the topology table? If so, immediately install it, begin routing to the alternative path, and update neighbors about the alternative. If no feasible successor exists, enter route recomputation If necessary, enter the route recomputation phase. Query neighbors for a alternative route –If neighbor has a feasible successor, it will send it to the router –If it does not have one, it will query all its directly connected neighbors, thus flooding the AS with the query until an alternate route is or is not found. Once the router has received replies from all queried neighbors, it can then recalculate the best route. –If a new alternative is found, it will be installed in the routing table. –If no new alternative is found, the old route is removed.

20. EIGRP Convergence Summary 1.Router detects link failure; enters route evaluation Feasible successors are promoted to successors Successors are installed in the routing table immediately All neighbors are updated about the new alternate route 2.If no feasible successors, router enters route recomputation Queries are flooded throughout the AS in search of an alternate All routers reply whether they have an alternative or not Originating router waits for all replies before either –Removing the queried network for its topology and routing tables or –Adding an alternative path for the queried network in its tables If a query receives no response, the route becomes “stuck-in-active” 3.The router has now converged and will now work to converge the entire internetwork by… Generating an update and multicasting it out all interfaces –Update contains info. on what paths the router has added/removed from its topology and routing tables Each receiving router will replay with an Ack packet and modify tables accordingly –The EIGRP internetwork has now converged.

21. Similar to IGRP, EIGRP is started with the following commands: Router(config)#router eigrp [AS_number] Router(config-router)#network network-number A router running both IGRP and EIGRP with the same AS number will automatically redistribute from one routing process into the other EIGRP routes redistributed into IGRP are denoted with an “ I ” in the routing table. IGRP routes redistributed into EIGRP are denoted with an “ D EX ” in the routing table. For interfaces whose actual bandwidth is different than EIGRP’s defaults, use the following command. Router(config-if)#bandwidth kilobits For example, a serial link defaults to T1 speeds or 1544 kbps. If the contracted speed is ½ a T1 or 768 kbps… Router(config-if)#bandwidth 768 Basic Configuration

22. Route Summarization EIGRP recognizes two types of summary routing: Automatic route summarization Manual route summarization Automatic Summarization (on by default in EIGRP) Works the same as IGRP and RIP Summarizes routes on the classful boundary; does not advertise subnets; subnets must be contiguous. For example; –Subnets 172.16.16.0/20, 172.16.32.0/20, and 172.16.48.0/20 would be automatically summarized as 172.16.0.0/16 Automatic summarization has its benefits –Conserves resources across classful boundaries in networks with proper IP addressing design. Manual Summarization EIGRP can summarize routes at classless boundaries on any router interface on the network This capability is an advantage over OSPF, which can only summarize on ABRs and ASBRs

23. Manual Summarization Automatic summarization must be turned off. in the routing process for EIGRP… Router(config-router)#no auto-summary To configure a classless summary route… Subnets must be contiguous!! Use the following command on the interface that will advertise the summary: Router(config-if)#ip summary-address eigrp AS-number ip-address mask

24. Manual Summarization Example On Router B, you would summarize routes advertised to A as follows: !Start the routing process & disable automatic summarization RTB(config)#router eigrp 100 RTB(config-router)#network 190.1.1.0 RTB(config-router)#network 190.1.2.0 RTB(config-router)#network 190.1.3.0 RTB(config-router)#no auto-summary !Then on the interface, summarize the subnets advertised to A RTB(config-router)#interface e0 RTB(config-if)#ip address 10.2.50.1 255.255.255.0 RTB(config-if)#ip summary-address eigrp 100 190.1.0.0 255.255.252.0 B A C D e0 e1 e2 190.1.1.0/24 190.1.3.0/24 190.1.2.0/24 10.2.10.0/24 10.2.50.0/24 190.1.0.0/22 Advertised to A

25. Null0 means there’s no specific interface for 190.1.1.0/22; more specific routes exist. Manual Summarization Example Router B’s topology table would show all the specific routes as well as the summary: RTB#show ip eigrp topology IP-EIGRP Topology Table for process 1 (output omitted) P 190.1.1.0/24, 1 successors, FD is 10511872 via Connected, Serial1 P 190.1.0.0/22, 1 successors, FD is 10511872 via Summary (10511872/0), Null0 P 190.1.3.0/24, 1 successors, FD is 10639872 via 190.1.1.1 (10639872/128256), Serial1 P 190.1.2.0/24, 1 successors, FD is 10537472 via 190.1.1.1 (10639872/128256), Serail1 B A C D e0 e1 s1 190.1.1.0/24 190.1.3.0/24 190.1.2.0/24 10.2.10.0/24 10.2.50.0/24 190.1.0.0/22 Advertised to A

26. Router A’s topology table would show only the summary route: Any packet destined for a network that is part of the 190.1.0.0/22 summary would be sent to Router B. RTA#show ip eigrp topology IP-EIGRP Topology Table for process 1 (output omitted) P 190.1.0.0/22, 1 successors, FD is 11023872 via 10.2.50.1 (11023872/10511872), Serial0 Manual Summarization Example B A C D e0 e1 s1 190.1.1.0/24 190.1.3.0/24 190.1.2.0/24 10.2.10.0/24 10.2.50.0/24 190.1.0.0/22 Advertised to A

27. Bandwidth Optimization By default, EIGRP will only consume up to 50% of a link’s configured bandwidth. If a link in 256Kbps, then EIGRP traffic will use up to 128Kbps Why would you want to change the default setting? May be necessary when network apps require certain amounts of bandwidth at all times. Sometimes, EIGRP traffic will require a certain level of bandwidth availability. Note: Changing EIGRP’s bandwidth percentage has no effect on user traffic. Two commands to configure EIGRP traffic percentage. bandwidth ip bandwidth-percent eigrp

28. bandwidth Configuration The bandwidth command Router(config-if)#bandwidth bandwidth Configured on the interface where you want to adjust EIGRP traffic. Whatever value is specified with the bandwidth command, EIGRP always takes 50% of it (by default). Remember: The bandwidth command is only used by routing protocols—it has no effect on user traffic when the protocol is EIGRP. The router does not use this command for any other purpose. For example, you have a 128kbps link and you only want EIGRP to use 16kbps. Router(config-if)bandwidth 32 EIGRP will use, at most, 50% of the configured bandwidth User traffic will still be allowed to use at least 112kbps (128-16)

29. AS # The second way to modify how much bandwidth EIGRP uses is to use the following command: Router(config-if)#ip bandwidth-percent eigrp AS-number percent Use this command when you want to specify a different percentage than 50% of the configured bandwidth. For example, you have a 64kbps link and the bandwidth has been set to 32kbps for metric calculation purposes. However, you want EIGRP to be able to use an entire 32kbps of the link’s 64kbps speed, if needed. Router(config)#int s0 Router(config-if)#bandwidth 32 Router(config-if)#ip bandwidth-percent eigrp 123 100 bandwidth-percent Configuration

30. NBMA Configurations NBMA Configuration Guidelines EIGRP should not exceed the CIR of the hub’s serial line (also called the access line). To do so is called “oversubscribing” the link Aggregate traffic of all links to the hub should no exceed the hub’s access line speed. Bandwidth on virtual circuits must be the same in both directions. Hub Router

31. Point-to-Point NBMA Example of point-to-point Frame Relay with EIGRP Each spoke router has a virtual circuit to the hub with a CIR of 256kbps. This is an oversubscribed situation. Why would you want to oversubscribe the spoke routers? To allow up to 256kbps across each spoke when traffic from other spokes is light. Configure the 10 subifs with bandwith of 154kbps so EIGRP will only use 50% of the subif when the NBMA is saturated with user traffic. 256k Access Line 1.544 Mbps

32. Point-to-Point Configurations Hub_Router(config)#interface serial 0 Hub_Router(config-if)#encapsulation frame-relay Hub_Router(config-if)#int serial0.1 point-to-point Hub_Router(config-subif)#bandwidth 154 Hub_Router(config-subif)#int serial0.2 point-to-point Hub_Router(config-subif)#bandwidth 154... Hub_Router(config-subif)#int serial0.10 point-to-point Hub_Router(config-subif)#bandwidth 154 256k Access Line 1.544 Mbps The above configuration insures EIGRP never uses more than 77kbps for EIGRP traffic Each Spoke Router must also be configured with the same bandwidth as the Hub Router.

33. Multipoint EIGRP In point-to-multipoint configurations... If the CIR of each Spoke Router is the same, set the access line’s bandwidth to the sum of the CIRs If the CIR of the Spoke Routers are different, which is the usual case, either... Take the lowest CIR and multiply it by the number of virtual circuits. This causes higher bandwidth links to be underutilized. Preferred Hybrid Solution: Use subinterfaces and configure like bandwidth virtual circuits on the same subinterface.

34. EIGRP & IPX Networks EIGRP can optimizes IPX updates. By default, IPX RIP and EIGRP routes are redistributed into each process. If IPX RIP and EIGRP have the same hop count, the IPX RIP route is believed unless both routes came from the same router. This ensure the router always believes an IPX server over a Cisco router. If EIGRP IPX is running on two neighbor routers, by default on... Serial links, SAP updates are only sent when a change occurs LAN links, SAP updates are sent periodically (60 sec) –You can configure incremental updates if... »all nodes out the interface are EIGRP peers and »the LAN link is not directly connected to an IPX server

35. EIGRP IPX Configurations EIGRP and IPX basic routing configurations Router(config)#ipx routing Router(config)#ipx router eigrp AS To disable IPX RIP updates for a particular network Since IPX RIP is on by default (no additional configurations are needed), to disable updates for a specific network... Router(config)#ipx router rip Router(config-ipx-router)#no network network-number To configure incremental SAP updates on LANs... Router(config-if)#ipx sap-incremental eigrp AS [rsup-only] rsup-only means IPX RIP routing is used. EIGRP is only used for SAP updates. EIGRP routes are ignored.

36. Monitoring EIGRP