cis185-ROUTE-lecture2-EIGRP-Part1

1

Please wait, CIS 185 will begin shortly… (5:30pm)There will be no sound until class begins. I will do a sound check at the beginning of class.

CIS 185 CCNP ROUTEEIGRP Part 1

Rick Graziani

Cabrillo College

[email protected]

Last Updated: Fall 2010

3

EIGRP Part 1

Review Neighbor Adjacencies and

EIGRP Reliability EIGRP Metric DUAL Basic EIGRP Configuration Passive-Interfaces Summarization Default Route

4

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

Review

6

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)

7

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

8

RTP and EIGRP Packet Types

What transport layer protocol does EIGRP use? Reliable Transport Protocol (RTP)

Why doesn’t EIGRP use UDP or TCP?

9

Protocol-Dependent Modules

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

10

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

11

Hello Protocol

NBMA Link that are

All other serial interfaces and LANs

12

Hello Protocol

Default hold time - 3 times the hello interval If the hold time expires:

EIGRP declares the route as down DUAL searches for a new path in the topology table or by

sending out queries. It is NOT automatically adjusted if Hello Interval is modified.

NBMA Link that are

All other serial interfaces and LANs

13

Update Packets – Reliable Delivery Acknowledgment (ACK) Packets – Unreliable Delivery

Sent when reliable delivery is used (update, query, and reply packets).

EIGRP uses triggered updates

EIGRP Packet Types – Update and Acknowledgement Packets

14

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.

15

DUAL: An Introduction

J. J. Garcia-Luna-Aceves

16

DUAL: An Introduction (More later!)

.

X Or holdtime expiresR2: Checks Topology table for Feasible Successor. If no FS…

17

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

18

Administrative Distance We will discuss Administrative

Distance in more detail in a later chapter.

Later in this chapter, you learn how to configure EIGRP summary routes.

Neighbor Adjacencies and EIGRP Reliability

19

20

Configuring Hello Intervals and Hold Times

Configurable on a per-interface basis, NOT per neighbor (LANs) Does not have to match with other EIGRP routers to establish

adjacencies.

Router(config-if)# ip hello-interval eigrp as-number seconds

Router(config-if)# ip hold-time eigrp as-number seconds

Neighbor Table Contents

H (handle)— Internal number used by the Cisco IOS. Order in which a neighboring (peering) session was established Starts with 0.

Address—The neighbor’s IP address. Interface—The outgoing interface on this router receiving hello packets for

the neighbor. Hold Time—The maximum time, in seconds, that the router waits to hear

from the neighbor without receiving anything from a neighbor before considering the link unavailable. Originally, had to be a hello packet, but in current Cisco IOS any EIGRP

packet received after the first hello from that neighbor resets the timer. Uptime—Time, in HH:MM:SS since the router first heard from this neighbor.

21


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.

22

Start

Stop

Start

Stop

No ACK Returned


Queue count—The number of EIGRP packets (update, query, and reply) waiting in the queue to be sent out. If this value is constantly higher than 0, a congestion problem might exist. 0 = no EIGRP packets in the queue.

Seq Num—The sequence number of the last update, query, or reply packet that was received from this neighbor. A sequence number is assigned to each reliable packet. An explicit ACK is required for that sequence number.

23

EIGRP Reliability 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.

24

Start

Stop

No ACK Returned

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.

16 x RTO < Hold Timer

EIGRP Reliability

25

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)

No ACK Received

Update 100

ACK

Update 101(in queue)

Update100

Multicast FlowTimer expires

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#

Update101

26


The show ip eigrp interfaces detail command displays a router's EIGRP Hello timer setting for each enabled interface.

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


1 10.0.0.5 Se0/0 13 01:09:52 607 3642 0 13


0 10.0.0.9 Se0/1 12 01:10:19 60 360 0 21


R3#

Initial Route Discovery

27

A B

Hello, I am Router A. Is anyone there?

Hello, I am Router B.

Here is all my routing information.I’m using split horizon.

Thanks for the information!That is very nice of you.

Here is all my routing information.I’m also using split horizon.

Thanks for the information!We’ve reached convergence.

EIGRPNeighborTable

EIGRPNeighborTable

EIGRPTopologyTable

EIGRPTopologyTable

IPRoutingTable

IPRoutingTable

Updated

Updated

Updated

Updated

Updated

Updated

Successor Successor

28

Router-ID

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 its loopback interfaces.

3. Highest active IP address of any of its physical interfaces.

Router(config)# router eigrp as

Router(config-router)# router-id ip-address

29

Forming Neighbor Adjacencies

Per interface/subinterface not per neighbor 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

The Metric

31

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.

32

Metric

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.

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>

K1 K2 K3 K4 K5

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.

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.

34

36

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

37

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.

Successors and Feasible Successors

38

Example 1: Best Path (Successor)? Feasible Successor?

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

FD = 6,500,000

FD = 3,500,000

Network X

FD = RD + additional Delay of serial link between R1 and neighbor. (This could also be due the slowest bandwidth.)

Which router is the successor?

39

Example 1

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

FD = 6,500,000

FD = 3,500,000

Network X

FD of 3,500,000 is the metric for network X in the routing table for R1.

Successor

Is R2 a feasible successor?

40

Example 1

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

FD = 6,500,000

FD = 3,500,000

Network X

RD of R2 is greater than FD through R3. Does not meet FC. No FS.

Successor

NOT a Feasible Successor

41

Example 1

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

Network X

Maybe R2’s path to Network X includes R1 - Loop

Successor


RX

42

Example 1

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

Network X

Or maybe R2’s does have a valid path to Network X. But R1 can’t tell because the distance vector update only gives it

distance and direction.

Successor


RX

43

Example 2: Best Path (Successor)? Feasible Successor?

R1

R2

R3

S0/0

S0/1

RD = 4,000,000

RD = 3,000,000

FD = 5,500,000

FD = 4,500,000

Network X

FD = RD + additional Delay of serial link between R1 and neighbor. (This could also be due the slowest bandwidth.)

Successor

Feasible Successor?

44

Example 2

R1

R2

R3

S0/0

S0/1

RD = 4,000,000

RD = 3,000,000

FD = 5,500,000

FD = 4,500,000

Network X

RD of R2 is less than (or equal to) the FD through R3. Meets FC, there is no loop back through R1. Is a FS.

Successor

Feasible Successor

45

XX

QueriesQueries

RepliesReplies

RtrF

RtrC

RtrE

RtrD

RtrB

RtrA

RtrG

If there are no Feasible Successors, the router must ask neighbors for help in hope of finding a new, loop-free path to the destination.

Neighbor routers are compelled to reply to this query. If a neighbor has a route, it will reply with information about the successor(s). If not, the neighbor notifies the sender that it doesn’t have a route to the destination

either.

Looking for new route

Query and Reply Packets

The topology

46

A

B

C

D

E

10.1.1.0/24

(1)

(1)

(2) (1)

(1)

(2)

Step 1

47

A

B

C

D

E

10.1.1.0/24

(1)

(1)

(2) (1)

(1)

(2)

Successor Feasible Successor (AD is less than FD)

Step 2

X

Router D: Sets the metric to network 10.1.1.0/24 as unreachable (–1 is unreachable). No FS (Feasible Successor) in the topology table, so the route changes from the passive

state to the Active state. Active state: Router sends out queries to neighboring routers looking for a new successor. Sends a query to Routers C and E for an alternative path to network 10.1.1.0/24. Marks Routers C and E as having a query pending (q).

Router E: DUAL marks the path to network 10.1.1.0/24 through Router D as Unusable. Router C: DUAL marks the path to network 10.1.1.0/24 through Router D as Unusable. 48

A

B

C

D

E

10.1.1.0/24

(1)

(2) (1)

(1)

(2)

Step 3

Q

Unusable

Unusable

Unreachable

Successor stillvia Router B

Successor stillvia Router A

Router D: DUAL receives a reply from Router C indicating no change to the path to 10.1.1.0/24 DUAL removes the query pending flag from Router C. DUAL stays Active on network 10.1.1.0/24, awaiting a reply from Router E to its query (q).

Router E: there is no FS to network 10.1.1.0/24, because the AD from Router C (3) is not less than the original FD (also 3). DUAL generates a query to Router C. DUAL marks Router C as query pending (q).

Router C: DUAL marks the path to network 10.1.1.0/24 through Router E as Unusable. 49

A

B

C

D

E

10.1.1.0/24

(1)

(2) (1)

(1)

(2)

Step 4

R

Q

Unusable

Unusable



50

A

B

C

D

E

10.1.1.0/24

(1)

(2) (1)

(1)

(2)

Step 5

Router D: DUAL stays active on network 10.1.1.0/24, awaiting a reply from Router E (q). Router E: DUAL receives a reply from Router C indicating no change.

It removes the query flag from Router C. It calculates a new FD and installs a new successor route in the topology table. It changes the route to network 10.1.1.0/24 from Active to Passive (converged).

R

Converged



Router D: DUAL receives a reply from Router E. It removes the query flag from Router E. It calculates a new FD. It installs new successor routes in the topology table.

Two routes (through Routers C and E) have the same FD, and both are marked as successors.

It changes the route to network 10.1.1.0/24 from Active to Passive (converged).

51

A

B

C

D

E

10.1.1.0/24

(1)

(2) (1)

(1)

(2)

Step 6

RConverged

Converged



Router D: Two successor routes are in the topology table for network 10.1.1.0/24. Both successor routes are listed in the routing table, and equal-cost load balancing is in

effect. The network is stable and converged. Successor No Feasible Successors

52

A

B

C

D

E

10.1.1.0/24

(1)

(2) (1)

(1)

(2)

Step 7



Basic EIGRP Configuration

54

Our Topology

55

Preconfigs

Configured on all routers.

R1(config)# no ip domain lookup

R1(config)# line con 0

R1(config-line)# exec-timeout 0 0

R1(config-line)# logging synchronous

56

R1

Bandwidth of 1,424 Kbps (1,424,000 bps) between R3 and R4 on bottom link

1544 configured on all serial links just in case.

interface FastEthernet0/0

ip address 192.168.10.1 255.255.255.0

!

interface Serial0/0

bandwidth 1544

ip address 10.0.0.1 255.255.255.252

clock rate 64000

!

interface Serial0/1

bandwidth 1544

ip address 10.0.0.5 255.255.255.252

57

R2


ip address 192.168.20.1 255.255.255.0

!

interface Serial0/0

bandwidth 1544

ip address 10.0.0.2 255.255.255.252

!

interface Serial0/1

bandwidth 1544

ip address 10.0.0.9 255.255.255.252

clock rate 64000

58

R3


ip address 192.168.30.1 255.255.255.0

!

interface Serial0/0

bandwidth 1544

ip address 10.0.0.6 255.255.255.252

clockrate 64000

!

interface Serial0/1

bandwidth 1544

ip address 10.0.0.10 255.255.255.252

!

interface Serial0/2

bandwidth 1544

ip address 10.0.0.13 255.255.255.252

clockrate 64000

!

interface Serial0/3

bandwidth 1424

ip address 10.0.0.17 255.255.255.252

clockrate 64000

59

R4


ip address 172.16.1.1 255.255.255.0

!

interface Serial0/0

bandwidth 1544

ip address 10.0.0.14 255.255.255.252

!


ip address 172.16.2.1 255.255.255.0

!

interface Serial0/1

bandwidth 1424

ip address 10.0.0.18 255.255.255.252

60

Configuring EIGRP – R1

Wildcard masks – Specifically tells EIGRP which interfaces to be enabled on.

If subnet mask is used IOS may convert it for the running-config.

Let’s do R2, R3 and R4 serial interfaces with wildcard masks…

R1(config)# router eigrp 1

R1(config-router)# network 10.0.0.0 0.0.0.3


R1(config-router)# network 192.168.10.0

61

Configuring EIGRP















62

Outputs

R3# show ip route

C 192.168.30.0/24 is directly connected, FastEthernet0/0

D 192.168.10.0/24 [90/2172416] via 10.0.0.5, 00:02:47, Serial0/0

D 172.16.0.0/16 [90/2172416] via 10.0.0.14, 00:02:39, Serial0/2

D 192.168.20.0/24 [90/2172416] via 10.0.0.9, 00:17:22, Serial0/1

10.0.0.0/30 is subnetted, 5 subnets

C 10.0.0.8 is directly connected, Serial0/1


D 10.0.0.0 [90/2681856] via 10.0.0.5, 00:02:57, Serial0/0

[90/2681856] via 10.0.0.9, 00:02:57, Serial0/1



Why does R3 prefer the top link to 172.16.0.0? It is 1,544 kbps link compared to 1,424 kbps link below

What do you notice aobut the 10.0.0.0 network? How many paths? R3 has equal cost paths to 10.0.0.0/30

63

Outputs

Does R3 see R4 as a neighbor on both links? Yes

R3# show ip eigrp neighbors



(sec) (ms) Cnt Num

3 10.0.0.18 Se0/3 13 00:17:37 24 200 0 5

2 10.0.0.14 Se0/2 14 00:17:50 29 200 0 4

1 10.0.0.5 Se0/0 14 00:23:35 607 3642 0 13

0 10.0.0.9 Se0/1 12 00:24:01 60 360 0 21

R3#

64

Outputs

Some other commands…

R3# show ip eigrp neighbors detail



(sec) (ms) Cnt Num

3 10.0.0.18 Se0/3 13 01:03:55 24 200 0 5


2 10.0.0.14 Se0/2 14 01:04:08 29 200 0 4


1 10.0.0.5 Se0/0 13 01:09:52 607 3642 0 13


0 10.0.0.9 Se0/1 12 01:10:19 60 360 0 21


R3#

65

Outputs

R3# show ip eigrp interfaces




Se0/1 1 0/0 60 0/15 299 0

Se0/0 1 0/0 607 0/15 3031 0

Se0/2 1 0/0 29 0/15 143 0

Se0/3 1 0/0 24 0/17 50 0

R3#

66


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

EIGRP maximum hopcount 100

EIGRP maximum metric variance 1

Redistributing: eigrp 1

Automatic network summarization is in effect

Maximum path: 4

Routing for Networks:

10.0.0.4/30

10.0.0.8/30

10.0.0.12/30

10.0.0.16/30

192.168.3.0

Routing Information Sources:

Gateway Distance Last Update

10.0.0.9 90 00:03:03

10.0.0.14 90 00:03:03

10.0.0.5 90 00:03:11

10.0.0.18 90 00:03:03

Distance: internal 90 external 170

What are these telling us?

K values

Variance, later

Directly connected networks

Neighbors

67

Outputs

R3# show ip eigrp topology

<output omitted>

P 10.0.0.0/30, 2 successors, FD is 2681856

via 10.0.0.9 (2681856/2169856), Serial0/1

via 10.0.0.5 (2681856/2169856), Serial0/0

<output omitted>

P 172.16.0.0/16, 1 successors, FD is 2172416

via 10.0.0.14 (2172416/28160), Serial0/2

via 10.0.0.18 (2312192/28160), Serial0/3successor

feasible successor

Feasible distance

Feasible distance: if this router was the successor.

Reported Distance is less than Feasible distance

68

Outputs

Why does R3 show a third entry for 10.0.0.0/30? Why is R4 a non-feasible successor?

Reported distance > Feasible distance There is a loop via the lower (1424kps) link!!!

R3# show ip eigrp topology all-links

P 10.0.0.0/30, 2 successors, FD is 2681856, serno 13

via 10.0.0.9 (2681856/2169856), Serial0/1

via 10.0.0.5 (2681856/2169856), Serial0/0

via 10.0.0.18 (3845632/3193856), Serial0/3

successor

successor

non-feasible successor

Passive Interfaces

70

Passive Interfaces

Two ways to prevent EIGRP from speaking sending EIGRP messages on an interface.

1. Enable EIGRP on the interface using the EIGRP network command and use the the passive-interface command. Does NOT send any EIGRP messages on the interface. No Hellos, thus no neighbor adjacency Prefix (interface subnet) is still advertised on other interfaces

2. Do NOT enable EIGRP on the interface, Advertise about the connected route using route redistribution

using the redistribute connected configuration command. More complicated Less popular

71

Passive Interfaces

R1# show ip eigrp inter




Se0/0 1 0/0 34 0/15 163 0

Se0/1 1 0/0 31 0/15 147 0

Fa0/0 0 0/0 0 0/10 0 0

The show ip eigrp interfaces command displays working interfaces on which EIGRP has been enabled, but omits passive interfaces.

A failure of the interface, or making the interface passive, would omit the interface from the output of this command.

72

Passive Interfaces

No longer a neighbor. Must include network command.


R1(config-router)# passive-interface fa 0/0

R1# show ip eigrp inter




Se0/0 1 0/0 32 0/15 151 0

Se0/1 1 0/0 28 0/15 139 0

R1#



73

Passive Interfaces

Verifying


<output omitted>


10.0.0.0/30

10.0.0.4/30

192.168.10.0

Passive Interface(s):

FastEthernet0/0

74

Passive Interfaces


R4(config-router)# passive-interface default

R4(config-router)# no passive-interface ser 0/0

R4(config-router)# no passive-interface ser 0/1


<output omitted>


10.0.0.12/30

10.0.0.16/30

172.16.0.0

Passive Interface(s):

FastEthernet0/0

FastEthernet0/1

Summarization

75

76

Summarization

Benefits: Smaller routing tables Reduces Query scope:

EIGRP Query stops at a router which has a summary route that includes the subnet listed in the Query, but not the specific route listed in the Query

EIGRP supports summarization on any router in the network Trade-offs:

Can cause suboptimal routing Packets destined for inaccessible destinations will flow to the

summarizing router before being discarded

Note: If a packet matches two routes in the routing table, the best match will be the route with the longest-bit-match, the route with the longer prefix-length (subnet mask).

77

EIGRP Summarization – Odds and Ends Any EIGRP router can summarize routes.

OSPF: Summarization can only take place on the ABRs and ASBRs.

The summary route's metric is based on the lowest metric route upon which the summary route is based. The summary route will use a metric equal to the metric of the

lowest metric subordinate route.

Manual summarization creates a Null0 summary on the router doing the summarization.

R3(config)# interface serial 0/0/1

R3(config-if)# ip summary-address eigrp 1 192.168.0.0 255.255.252.0

R3# show ip route

<output omitted>

D 192.168.0.0/22 is a summary, 00:00:06, Null0

Creates a Null0 summary route

78

The Null0 Summary Route

EIGRP automatically includes a Null0 summary route as a child route whenever both of the following conditions exist: There is at least one subnet that was learned via EIGRP. Automatic summarization is enabled. (By default with EIGRP)

What if R1 received a packet: 172.16.4.10 It would be discarded – never looking for a supernet or default route Regardless of ip classless or no ip classless command

Helps prevent any routing loops between the edge and ISP routers.

R1# show ip route

192.168.10.0/24 is variably subnetted, 3 subnets, 2 masks


C 192.168.10.4/30 is directly connected, Serial0/0/1

D 192.168.10.8/30 [90/3523840] via 192.168.10.6, 00:44:56, S0/0/1




D 172.16.2.0/24 [90/40514560] via 172.16.3.2, 00:45:09, S0/0/0


D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 00:44:55, Serial0/0/1

79

Disabling Automatic Summarization

Like RIP, EIGRP automatically summarizes at major network boundaries using the default auto-summary command.

R3# show ip route





D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0


172.16.0.0/16

80


Both R1 and R2 automatically summarizing. R1 is the successor because of the difference in bandwidth.

R3# show ip route





D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0


172.16.0.0/16

172.16.0.0/16

81


Is this the best route for all 172.16.0.0 subnets? No, suboptimal routing may occur. R3 will route all packets destined for 172.16.2.0 through R1.

Solution? Need R1 and R2 to send individual subnets. R1 and R2 must stop automatically summarizing 172.16.0.0/16.

R3# show ip route

<output omitted>

D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0

172.16.0.0/16

82


Automatic summarization can be disabled with the no auto-summary. The router configuration command eigrp log-neighborchanges is on by

default on some IOS implementations. .


R1(config-router)# no auto-summary

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is resync: summary configured

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is down: peer restarted

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is up: new adjacency

<output omitted>





83

R1 no more Null0 summary routes:


D 172.16.0.0/16 is a summary, 00:46:10, Null0 What does this mean?

This means any packets for their parent networks that do not match a child route, the routing table will check supernet and default routes.

Unless no ip classess is used

R1# show ip route


C 192.168.10.4 is directly connected, Serial0/0/1

D 192.168.10.8 [90/3523840] via 192.168.10.6, 00:16:55, S0/0/1



D 172.16.2.0/24 [90/3526400] via 192.168.10.6, 00:16:53, S0/0/1


D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 00:16:52, Serial0/0/1


84

R2 no more Null0 summary routes :



R2# show ip route


D 192.168.10.4 [90/3523840] via 192.168.10.10, 00:15:44, S0/0/1



D 172.16.1.0/24 [90/3526400] via 192.168.10.10, 00:15:44, S0/0/1




C 10.1.1.0 is directly connected, Loopback1

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 00:15:44, S0/0/1


85

Why does R3’s routing table now have two equal-cost paths to 172.16.3.0/24? Shouldn’t the best path only be through R1 with the 1544-Mbps link?

R3# show ip route





D 172.16.1.0/24 [90/2172416] via 192.168.10.5, 00:00:11, S0/0/0

D 172.16.2.0/24 [90/3014400] via 192.168.10.9, 00:00:12, S0/0/1

D 172.16.3.0/30 [90/41024000] via 192.168.10.5, 00:00:12, S0/0/0

[90/41024000] via 192.168.10.9, 00:00:12, S0/0/1


172.16.0.0/16

172.16.0.0/16

86


The slowest link is the 64-Kbps link

R3# show ip route

<output omitted>

D 172.16.3.0/30 [90/41024000] via 192.168.10.5, 00:00:12, S0/0/0

[90/41024000] via 192.168.10.9, 00:00:12, S0/0/1

172.16.0.0/16

172.16.0.0/16

87

Manual Summarization

EIGRP can be configured to summarize routes, whether or not automatic summarization (auto-summary) is enabled.

Modified topology.

88


Add two more networks to R3. Configure EIGRP network statements.

R3(config)# interface loopback 2

R3(config-if)# ip address 192.168.2.1 255.255.255.0

R3(config-if)# interface loopback 3

R3(config-if)# ip address 192.168.3.1 255.255.255.0

R3(config-if)# router eigrp 1



89


Instead of sending three separate networks, R3 can summarize the 192.168.1.0/24, 192.168.2.0/24, and 192.168.3.0/24 networks as a single route.

R1# show ip route

D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 02:07:38, S0/0/1

D 192.168.2.0/24 [90/2297856] via 192.168.10.6, 00:00:34, S0/0/1

D 192.168.3.0/24 [90/2297856] via 192.168.10.6, 00:00:18, S0/0/1

R2# show ip route

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 02:08:50, S0/0/1

D 192.168.2.0/24 [90/3139840] via 192.168.10.10, 00:01:46, S0/0/1

D 192.168.3.0/24 [90/3139840] via 192.168.10.10, 00:01:30, S0/0/1

Only pertinent routes shown

192.168.1.0/24, 192.168.2.0/24,

192.168.3.0/24 192.168.1.0/24, 192.168.2.0/24,

192.168.3.0/24

90

Determining the Summary EIGRP Route

1. Write out the networks that you want to summarize in binary.2. Find the matching bits.

Count the number of leftmost matching bits, which in this example is 22. This number becomes your subnet mask for the summarized route: /22

or 255.255.252.0.3. To find the network address for summarization, copy the matching 22 bits

and add all 0 bits to the end to make 32 bits.

The result is the summary network address and mask for 192.168.0.0/22

91

Configure EIGRP Manual Summarization

Because R3 has two EIGRP neighbors, the EIGRP manual summarization in configured on both Serial 0/0/0 and Serial 0/0/1.

Router(config-if)# ip summary-address eigrp as-number network-address subnet-mask





192.168.0.0/22

192.168.0.0/22

R3# show ip route

<output omitted>


Creates a Null0 summary route

92

Verify EIGRP Manual Summarization

Fewer number of total routes in routing tables Faster routing table lookup process more efficient.

Summary routes also require less bandwidth and memory Single route can be sent rather than multiple individual routes.

NOTE: The minimum metric of specified routes is used as the metric of the summary route.

R1# show ip route

<output omitted>

D 192.168.0.0/22 [90/2172416] via 192.168.10.6, 00:01:11, Serial0/0/1

R2# show ip route

<output omitted>

D 192.168.0.0/22 [90/3014400] via 192.168.10.10, 00:00:23, Serial0/0/1

192.168.0.0/22

192.168.0.0/22

Default Route

93

94

EIGRP Default Route

R2(config)# ip route 0.0.0.0 0.0.0.0 loopback 1


R2(config-router)# redistribute static

The ISP router in our topology does not physically exist. By using a loopback interface, we can simulate a connection to another router.

Default RouteRedistribute default static route in EIGRP updates

Unlike RIP and OSPF, EIGRP does not propagate a 0.0.0.0 0.0.0.0 by default.

Two ways to propagate a static default route in EIGRP: Redistribute static Network command

redistribute static will redistribute all static routes by default.

95

EIGRP Default Route

R1# show ip route

Gateway of last resort is 192.168.10.6 to network 0.0.0.0

D*EX 0.0.0.0/0 [170/3651840] via 192.168.10.6, 00:02:14, S0/0/1

Only static default route shown, other output omitted.

D: This static route was learned from an EIGRP routing update. *: The route is a candidate for a default route. EX: The route is an external EIGRP route, in this case a static route outside

of the EIGRP routing domain. 170: This is the AD of an external EIGRP route.


96

EIGRP Default Route

R2(config)# ip route 0.0.0.0 0.0.0.0 loopback 1



Default Route

The network 0.0.0.0 command will propagate a default route as a result of the static default route.

97

EIGRP Default-network

There is another method to propagate a default route in EIGRP, using the ip default-network command.


98

EIGRP Default- network

R2(config)# ip default-network 10.0.0.0





default-network

ip default-network network-number network-number - Network of last-resort gateway that will be announced to all

other routers. R2’s routing table:

10.0.0.0 will be shown as the “gateway of last resort” This network is propagated in EIGRP as a “gateway of last resort” If a subnet is specified IOS will install a static route in the running-config

A few commands…

99

show ip eigrp traffic

Displays the number of various EIGRP packets sent and received

100

debug ip eigrp traffic Displays the types of

EIGRP packets sent and received by the router on which this command is executed.

See example in Chapter 2 for a detailed explanation of this output.

101

debug ip eigrp

Displays general debugging information.

See example in Chapter 2 for a detailed explanation of this output.

102

103

That’s all for tonight, good night!

CIS 185 CCNP ROUTEEIGRP Part 1

Rick Graziani

Cabrillo College

[email protected]

Last Updated: Fall 2010

cis185-ROUTE-lecture2-EIGRP-Part1

Documents

Transcript of cis185-ROUTE-lecture2-EIGRP-Part1