EIGRP

1. EIGRP Brigham Young University- Idaho CIT 340

2. EIGRP • EIGRP Concepts • EIGRP Configuration • Troubleshooting Routing Protocols

3. EIGRP Overview • Cisco proprietary protocol, advanced version of IGRP • Hybrid Routing protocol (best of SPF and Distance vector) • Supports CIDR/VLSM • Supports multiple routed protocols independently • Uses DUAL (Diffusing Update Algorithm) to calculate routes.

4. Similarities Both developed by Cisco Both calculate metrics using bandwidth and delay Use autonomous system numbers Differences EIGRP scales metric of IGRP by a factor of 256 (EIGRP=32 bits, IGRP=24 bits) Hop count, IGRP=255, EIGRP=224 EIGRP supports CIDR/VLSM EIGRP offers multi-protocol support EIGRP vs. IGRP

5. IGRP and EIGRP: A migration path

6. EIGRP Concepts and Terminology • Like OSPF, EIGRP saves data in RAM in one of several databases for fast availability. • Three databases are: • Neighbor table • Topology table • Routing table

7. Neighbor Table • Lists adjacent routers. A table is created for each protocol EIGRP supports. (IP, IPX) • Neighbor routers Interface and address are recorded. • Hold time information received from HELLO packets determine if route is still accessible or route changes need to be made. • Number of packets waiting to be sent.

8. Neighbor Table • The following fields are found in the Neighbor Table • Neighbor address • Hold time • Smooth Round-Trip Timer (SRTT) • Queue count (Q Cnt) • Sequence Number (Seq No)

9. Topology Table • Made up of all EIGRP routing tables from Autonomous system. • DUAL uses this information to determine the best routes to a destination. (Successor Route) • A separate topology table is created for each network protocol supported.

10. Topology Table Contents • Feasible Distance-the lowest calculated metric to each destination. • Route source-identification number of the router that originally advertised that route. Only used routes originated outside of EIGRP. • Reported distance-the distance reported by an adjacent neighbor • Interface information– The interface through which the destination is reachable • Router Status- A (Active), P (Passive) • Routing Protocol used

11. DUAL

12. DUAL finite-state machine algorithm • Diffusing Update Algorithm is the EIGRP route-calculation engine. • Tracks all the routes advertised by neighbors, uses composite metrics to compare them and determine if they are loop-free.

13. Routing Table • Holds best routes to each destination. • Maintains separate table for each supported protocol. • Successor routes- Route selected to destination.

14. EIGRP Design Features • Rapid convergence-DUAL provides Loop-free operation with all routers being updated at same time. • Efficient use of bandwidth-Sends Partial-Bounded updates only to those routers who need updates. • Supports multiple protocols-IP, IPX and AppleTalk are supported through Protocol-dependant Modules, PDM’s. Modules can change but EIGRP can stay the same.

15. EIGRP Technologies • Neighbor discovery and recovery • Reliable Transport Protocol • DUAL finite-state machine algorithm • Protocol-dependent modules

16. Protocol-Dependent Modules (PDMs)

17. Neighbor Discovery/Recovery • Like OSPF, EIGRP establishes neighbor relationships. • Establish adjacencies by sending Hello Packets • 5 seconds-High-speed links >1.5MHz (default) • 60 Seconds-Low-speed links <1.5MHz • Hello Packets are multicast to address 224.0.0.10

18. Establishing Adjacencies with Neighbors By forming adjacencies, EIGRP routers do the following: • Dynamically learn of new routes that join their network • Identify routers that become either unreachable or inoperable • Rediscover routers that had previously been unreachable

19. Neighbor Discovery/Recovery • EIGRP has a Hold-time used to determine when Hello packets are no longer being received. • If Hello packets are being received, EIGRP assumes route is available. Marked a Passive. • If hold-time is past, EIGRP must rediscover route. Marked as Active. • Hello packets are sent unreliably

20. EIGRP Data Structure • The five EIGRP packet types are: • Hello • Acknowledgment • Update • Query • Reply

21. Acknowledgement Packets • EIGRP is Routed-protocol independent. • Reliable Transport Protocol (RTP) provides acknowledgement of all packets sent. • Acknowledgement packets are Hello packets without data. • Acknowledgement packets are Unicast.

22. Reliable Transport Protocol • EIGRP is protocol-independent; that is, it doesn’t rely on TCP/IP to exchange routing information the way RIP, IGRP, and OSPF do. • To stay independent of IP, EIGRP uses the transport-layer protocol to guarantee delivery of routing information: RTP. • RTP supports: • Reliable delivery: Delivery guaranteed and in order, Cisco proprietary algorithm known as reliable multicast, and are Acknolwedged • Unreliable delivery • RTP supports unicasting and multicasting (224.0.0.10) • Neighbors that receive a reliable multicast packet unicasts an acknowledgement • Reliable RTP is used for EIGRP queries, updates and replies (usually meant when referred to using RTP) • Unreliable RTP is used for EIGRP Hello’s and Ack’s • If any packet is reliably multicast and an ACK is not received from a neighbor, the packet will be retransmitted as a unicast to that unresponding neighbor. • If an ACK is not received after 16 of theses unicast transmissions, the neighbor will be declared dead.

23. Update Packets • Update packets are used when a new neighbor is located or when the topology changes. • New neighbor packets are Unicast • Topology changes are Multicast. • Update packets are sent reliably.

24. Query Packets • Query packets are used to gain specific information from a neighbor. • If a router loses it’s successor route and cannot determine a feasible successor, query packets are multicast to all neighbors searching for a new route.

25. Reply Packets • Reply packets are responses to query packets. • If a router receives a query from a router looking for a new route, it must send a reply, indicating a new route or that no info is available. • Replies are Unicast.

26. Configuring EIGRP router(config)#router eigrpautonomous-system-number Router(config)#router eigrp 101 • Autonomous system number indicates all routers belonging to the Internetwork. Must be the same for IGRP and EIGRP to share information

27. Configuring EIGRP • router(config-router)#networknetwork-number router(config-router)# network 10.0.0.0 Network 192.168.15.0 • Network addresses are written in a classful manner

28. Configuring EIGRP • router(config-if)#bandwidthkilobits router(config-if)# bandwidth 64 • Should be configured on Serial links so that convergence happens quickly. Mismatched bandwidth will cause network problem

29. Configuring EIGRP • router(config-if)#eigrp log-neighbor-changes • This command enables the logging of neighbor adjacency changes to monitor the stability of the routing system and to help detect problems.

30. EIGRP Summarization • EIGRP summarizes networks at the Classful boundary. • This may be a problem in discontinuous networks. • Auto-summarization can be turned off with the following command. router(config-router)#no auto-summary

31. Summarizing EIGRP Routes: no auto-summary • EIGRP automatically summarizes routes at the classful boundary, the boundary where the network address ends as defined by class-based addressing.

32. Summarizing EIGRP Routes: no auto-summary • In the presence of discontiguous subnetworks, automatic summarization must be disabled for routing to work properly. • To turn off auto-summarization, use the following command: Router(config-router)#no auto-summary

33. Verifying EIGRP • Show IP EIGRP neighbor • Displays neighbor table • Show IP EIGRP Interfaces • Displays EIGRP info for all interfaces running EIGRP • Show IP EIGRP Topology • Displays feasible successors

34. Troubleshooting EIGRP • Verify EIGRP configuration with the following commands: • show running-configuration • show ip protocols • show ip eigrp neighbors