CIS 185 CCNP ROUTE EIGRP Part 1

1. CIS 185 CCNP ROUTEEIGRP Part 1 Rick Graziani Cabrillo College graziani@cabrillo.edu Last Updated: Fall 2011

2. EIGRP Part 1 • Review • Neighbor Adjacencies and EIGRP Reliability • EIGRP Metric • DUAL • Basic EIGRP Configuration • Passive-Interfaces • Summarization • Default Route

3. Materials • Book: • Implementing Cisco IP Routing (ROUTE) Foundation Learning Guide: Foundation learning for the ROUTE 642-902 Exam • By Diane Teare • Book • ISBN-10: 1-58705-882-0 • ISBN-13: 978-1-58705-882-0 • eBook • ISBN-10: 0-13-255033-4 • ISBN-13: 978-0-13-255033-8

4. Review

5. What do we remember about EIGRP? • What type of protocol is EIGRP? • Distance Vector • What are the default metrics used by EIGRP? • Bandwidth (slowest) and Delay (cumulative) • What are the optional metrics? • Reliability and Load • Note: Book also state MTU but it is not a metric. • What algorithm is used to determine best path? • DUAL (Diffusing Update Algorithm)

6. Review of EIGRP from CCNA • Enhanced Interior Gateway Routing Protocol (EIGRP) • Released in 1992 with Cisco IOS Software Release 9.21. • Enhancement of Cisco’s: • Interior Gateway Routing Protocol (IGRP). • Both are Cisco proprietary, operate only on: • Cisco routers

7. RTP and EIGRP Packet Types • What transport layer protocol does EIGRP use? • Reliable Transport Protocol (RTP) • Why doesn’t EIGRP use UDP or TCP?

8. Protocol-Dependent Modules • EIGRP uses protocol-dependent modules (PDM). to route different protocols, including: • IPv4 • IPv6 • Internetwork Packet Exchange (IPX) • AppleTalk

9. EIGRP Packet

10. EIGRP Header

11. EIGRP Packet

12. EIGRP Packet Types – Hello Packet • What are Hello packets used for by EIGRP to: • Discover neighbors (sometimes called neighborships) • Form adjacencies with those neighbors • What is the multicast address? Hint: 224.0.0.? • 224.0.0.10 • Are these sent as reliable or unreliable deliver? • Unreliable delivery – No ACKs returned

13. Hello Protocol NBMA Link that are All other serial interfaces and LANs

14. Hello Protocol NBMA Link that are All other serial interfaces and LANs • Default hold time - 3 times the hello interval • If the hold timeexpires: • EIGRP declares the route as down • DUAL searches for a new path in the topology tableor by sending out queries. • It is NOT automatically adjusted if Hello Interval is modified.

15. EIGRP Packet Types – Update and Acknowledgement Packets EIGRP uses triggered updates • Update Packets – Reliable Delivery • Acknowledgment (ACK) Packets – Unreliable Delivery • Sent when reliable delivery is used (update, query, and reply packets).

16. EIGRP Packet Types – Query and Reply Packets • Queries and replies use reliable delivery (Ack returned). • Used by DUAL when searching for networks and other tasks.

17. DUAL: An Introduction J. J. Garcia-Luna-Aceves

18. DUAL: An Introduction (More later!) R2: Checks Topology table for Feasible Successor. If no FS… X Or holdtime expires .

19. Summary - RTP Packet Types • Hellos– Identifies neighbors • Used by the neighbor discovery and recovery process. • Multicast • Unreliable delivery • Acknowledgements (ACK) – Acknowledges receipt • Hello packets with no data • Unicast • Unreliable delivery • Updates – Advertises routes • Transmitted only when necessary • Unicast when sent to a specific router • Multicast when sent to multiple routers • Reliable delivery • Queries – Ask about a route (DUAL) • Reliable delivery • Multicast or Unicast • Queries and Replies – Ask about a route and answer a query (DUAL) • Reliable delivery • Replies: Unicast

20. Administrative Distance Routes manually summarized. • We will discuss Administrative Distance in more detail in a later chapter. • Later in this chapter, you learn how to configure EIGRP summary routes. Routes redistributed into EIGRP.

21. Neighbor Adjacencies and EIGRP Reliability

22. Configuring Hello Intervals and Hold Times Router(config-if)# ip hello-intervaleigrpas-number seconds Router(config-if)# ip hold-time eigrp as-number seconds • Configurable on a per-interface basis, NOT per neighbor (LANs) • Does not have to match with other EIGRP routers to establish adjacencies.

23. Neighbor Table Contents SRTT (Smooth Round Trip Timer) and RTO (Retransmit Interval) are used by RTP to manage reliable EIGRP packets. SRTT indicates how long it takes for this neighbor to respond to reliable packets. RTO indicates how long to wait before retransmitting if no ACK is received. R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.102 Se0/0/1 11 00:07:22 10 2280 0 5 R1# Neighbor’s IP address Queue count should always be zero otherwise there’s congestion on the link. The sequence number of the last update, query, or reply packet that was received from this neighbor. Amount of time since this neighbor was added to the neighbor table. Local interface receiving EIGRP Hello packets. Lists the order in which a peering session was established with the specified neighbor, starting with 0. Seconds remaining before declaring neighbor down. The current hold time and is reset to the maximum hold time whenever a Hello packet is received.

24. Start Stop Neighbor Table Contents Start Stop • Smooth Round Trip Timer (SRTT)—The average number of milliseconds it takes for an EIGRP packet to be sent to this neighbor and for the local router to receive an acknowledgment of that packet. • Used to determine the retransmit interval, a.k.a. retransmit timeout (RTO). • RTO—The amount of time, in milliseconds, that the router waits for an acknowledgment before retransmitting a reliable packet from the retransmission queue to a neighbor. No ACK Returned

25. Start Stop EIGRP Reliability No ACK Returned 16 x RTO < Hold Timer • If the RTO expires before and ACK is received, EIGRP retransmits another copy of the packet. • A maximum of 16 times OR until the hold time expires then the Neighbor is declared down. • When a neighbor is declared down: • The adjacency is removed • All networks reached through that neighbor are removed from the routing table. • 180 second hold time on low-speed NBMA links can be a long time to wait. • Retransmission occurs after each RTO timer expires. • After 16 attempts the neighbor is declared down. • This is less time than waiting for the hold time to expire. • RTO—The amount of time, in milliseconds, that the router waits for an acknowledgment before retransmitting a reliable packet from the retransmission queue to a neighbor. • Updates, queries and replies are sent reliably. • A sequence number is assigned and an explicit ACK is returned for each sequence number.

26. Update101 EIGRP Reliability ACK Update 100 Update100 Update 101 (in queue) No ACK Received Multicast Flow Timer expires • Potential problem on multiaccess (Frame Relay, Ethernet) media where multiple neighbors reside. • The next reliable multicast packet cannot be sent until all peers have Acknowledged the previous multicast packet. • If one or more neighbors are slow to respond it adversely affects all peers. • When a neighbor is slow to respond to multicasts or does not acknowledge the multicast, the router will retransmit the packet as a unicast. • This allows reliable multicasts to continue and speeds up convergence without waiting for peers on lower speed links. • Multicast flow timer - Determines how long a router should wait for an ACK to be received before switching from multicast to unicast. • Calculation is based on RTO and SRTT (Cisco proprietary) R3# show ip eigrp interfaces IP-EIGRP interfaces for process 1 Xmit Queue Mean Pacing Time Multicast Pending Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes Se0/1 1 0/0 60 0/15 299 0 Se0/0 1 0/0 607 0/15 3031 0 R3#

27. Neighbor Table Contents R3# show ip eigrp neighbors detail IP-EIGRP neighbors for process 1 H Address Interface Hold Uptime SRTT RTO Q Seq Type (sec) (ms) Cnt Num 3 10.0.0.18 Se0/3 13 01:03:55 24 200 0 5 Version 12.3/1.2, Retrans: 2, Retries: 0 2 10.0.0.14 Se0/2 14 01:04:08 29 200 0 4 Version 12.3/1.2, Retrans: 1, Retries: 0 1 10.0.0.5 Se0/0 13 01:09:52 607 3642 0 13 Version 12.3/1.2, Retrans: 0, Retries: 0 0 10.0.0.9 Se0/1 12 01:10:19 60 360 0 21 Version 12.3/1.2, Retrans: 0, Retries: 0 R3# • The show ip eigrp interfaces detail command displays a router's EIGRP Hello timer setting for each enabled interface.

28. Initial Route Discovery A B Updated Updated EIGRP Neighbor Table EIGRP Neighbor Table Hello, I am Router A. Is anyone there? Hello, I am Router B. Here is all my routing information. I’m using split horizon. Updated Updated EIGRP Topology Table EIGRP Topology Table Thanks for the information! That is very nice of you. Successor Successor Here is all my routing information. I’m also using split horizon. Updated Updated IP Routing Table IP Routing Table Thanks for the information! We’ve reached convergence.

29. Example: EIGRP Tables Router C’s tables:

30. Router-ID Router(config)# routereigrpas Router(config-router)# router-idip-address • EIGRP Router ID is an IP address used to uniquely identify an EIGRP router. 1. Use the IP address configured with the EIGRP router-id command. 2. Highest IP address of any of itsloopback interfaces. 3. Highest active IP address of any of its physical interfaces.

31. Forming Neighbor Adjacencies • The following are the most common causes of problems with EIGRP neighbor relationships: • Unidirectional link • Uncommon subnet, primary, and secondary address mismatch • Mismatched masks • K value mismatches • Mismatched AS numbers • Stuck in active • Layer 2 problem • Access list denying multicast packets • Manual change (summary router, metric change, route filter) • Does NOT prevent neighbor relationships • Hello and Hold timer setting mismatch • Duplicate router IDs • IP MTU mismatch

32. The Metric

33. EIGRP Message

34. EIGRP Message - TLVs

35. TLV 0x0001 - EIGRP Parameters • K values are used to calculate the EIGRP metric. • The Hold Time advertised by a neighbor is the maximum time a router should wait for any valid EIGRP message sent by that neighbor before declaring it dead.

36. TLV 0x0002 - Internal IP Routes • Delay: Sum of delays in units of 10 microseconds from source to destination. • Bandwidth: Lowest configured bandwidth on any interface along the route. • Prefix length: Specifies the number of network bits in the subnet mask. • Destination: The destination address of the route.

37. TLV 0x0003 - External IP Routes • Fields used to track external source of route. • IP external routes are routes which are imported into EIGRP through redistribution of a default route or other routing protocols. • Same fields contained in the Internal IP route TLV (0x0002).

38. Metric • By default, K1 and K3 are set to 1, and K2, K4, and K5 are set to 0. • The result is that only the bandwidth and delay values are used in the computation of the default composite metric. • Reliability and Load are optional metrics. • MTU is NOT a metric, never has been, never will be.

39. Metric R1# show ip protocols Routing Protocol is “eigrp 1” Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Default networks flagged in outgoing updates Default networks accepted from incoming updates EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 <output omitted> • The K values on R1 are set to the default. • Changing these values to other than the default is not recommended unless the network administrator has a very good reason to do so. • Cisco recommends that these values are not modified. K1 K2 K3 K4 K5

40. Metric: Displaying Interface Values SanJose2> show interface s0/0 Serial0/0 is up, line protocol is up Hardware is QUICC Serial Description: Out to Westasman Internet address is 192.168.64.5/30 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 246/255 <output omitted> • EIGRP bandwidth uses the minimum bandwidth link represented in 107 divided by the kilobits per second. • Show interfaces displays bandwidth in kilobits per second. • EIGRP delay value is the sum of delays in tens of microseconds multiplied by 256. • Show interfaces displays delay in microseconds.

41. Metric Calculation • For a review and examples of how the EIGRP metric is calculate read Chapter 2 EIGRP, “EIGRP Metric Calculation” or review my CIS 82 PowerPoint presentations on EIGRP.

42. DUAL

43. EIGRP Operations List of directly connected adjacent EIGRP neighbor routers and the local interface to exit to reach it. • EIGRP selects primary (successor) and backup (feasible successor) routes and injects those into the topology table. • The primary (successor) routes are then moved to the routing table. List of all routes learned from each EIGRP neighbor and identifies successor routes and feasible successor routes. List of the best (successor) routes from the EIGRP topology table and other routing processes.

44. Example: EIGRP Tables

45. DUAL Concepts • Diffusing Update Algorithm is the algorithm used by EIGRP. • Determines: • best loop-free path • loop-free backup paths (which can be used immediately) • DUAL also provides the following: • Fast convergence • Minimum bandwidth usage with bounded updates • DUAL uses several terms that are discussed in more detail throughout this section: • Successor • Feasible distance • Feasible successor • Reported distance or advertised distance • Feasible condition or feasibility condition

46. Successors and Feasible Successors Feasible distance (FD) is the minimum distance (metric) along a path to a destination network. Reported distance (RD or AD) is the distance (metric) towards a destination as advertised by an upstream neighbor. Reported distance is the distance reported in the queries, the replies and the updates. A neighbor meets the feasible condition (FC) if the reported distance by the neighbor is less than the current feasible distance (FD) of this router. "If a neighbors metric is less than mine, then I know the neighbor doesn't have a loop going through me." A feasible successor is a neighbor whose reported distance (RD) is less than the current feasible distance (FD). Feasible successor is one who meets the feasible condition (FC). Your route (metric) to the network (RD to me) must be LESS than my current route (my total metric) to that same network. If your route (metric) to the network (RD to me) is LESS than my current route (my total metric), I will include you as a FEASIBLE SUCCESSOR. If your route (metric) to the network (RD to me) is MORE than my current route (my total metric), I will NOT include you as a FEASIBLE SUCCESSOR.

47. Example 1: Best Path (Successor)? Feasible Successor? RD = 6,000,000 Which router is the successor? R2 FD = 6,500,000 Network X S0/0 R1 S0/1 • FD = RD + additional Delay of serial link between R1 and neighbor. (This could also be due the slowest bandwidth.) FD = 3,500,000 R3 RD = 3,000,000

48. Example 1 RD = 6,000,000 Is R2 a feasible successor? R2 FD = 6,500,000 Network X S0/0 R1 S0/1 • FD of 3,500,000 is the metric for network X in the routing table for R1. FD = 3,500,000 Successor R3 RD = 3,000,000

49. Example 1 NOT a Feasible Successor RD = 6,000,000 R2 FD = 6,500,000 Network X S0/0 R1 S0/1 • RD of R2 is greater than FD through R3. • Does not meet FC. • No FS. FD = 3,500,000 Successor R3 RD = 3,000,000

50. Example 1 RX NOT a Feasible Successor RD = 6,000,000 R2 Network X S0/0 R1 S0/1 • Maybe R2’s path to Network X includes R1 - Loop Successor R3 RD = 3,000,000