1. CIS 185 CCNP ROUTE Chapter 2: Implementing EIGRP
Rick Graziani
Cabrillo College
Spring 2017

2. Basic EIGRP

3. Types of Routing Protocols
Exterior Gateway Protocols
Interior Gateway Protocols
Distance Vector
Link State
Path Vector
Distance Vector Routing Protocols
Link State Routing Protocols
Path Vector
RIPv2
EIGRP
OSPFv2
IS-IS
BGP-4
RIPng
EIGRP for IPv6
OSPFv3 *
IS-IS for IPv6
BGP-4 for IPv6 or
MP-BGP
IPv4
IPv6
* OSPFv3 supports routing both IPv4 and IPv6.

4. /24
Topology
/24
/24

5. Initial Config – R1 interface GigabitEthernet0/0
ip address !
interface Serial0/0/0
description R1-->R2
bandwidth 64
ip address
clock rate 64000
interface Serial0/0/1
description R1-->R3
bandwidth 1544
ip address

6. Initial Config – R2 interface GigabitEthernet0/0
ip address !
interface Serial0/0/0
description R2-->R1
bandwidth 64
ip address
interface Serial0/0/1
description R2-->R3
bandwidth 1024
ip address
clock rate 64000

7. Initial Config – R3 interface GigabitEthernet0/0
ip address !
interface Serial0/0/0
description R3-->R1
bandwidth 1544
ip address
clock rate 64000
interface Serial0/0/1
description R3-->R2
bandwidth 1024
ip address

8. Configuring Basic EIGRP
R1(config)# router eigrp 1
R1(config-router)# network
R1(config-router)# network
R1(config-router)#
R2(config)# router eigrp 1
R2(config-router)# network
R2(config-router)# network
R2(config-router)# /
R3(config)# router eigrp 1
R3(config-router)# network
R3(config-router)# network
R3(config-router)# network
R3(config-router)#

9. EIGRP Router ID R1(config)# router eigrp 1
R1(config-router)# eigrp router-id
R2(config)# router eigrp 1
R2(config-router)# eigrp router-id
R3(config)# router eigrp 1
R3(config-router)# eigrp router-id
*Feb 1 20:00:37.883: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/0) is down: route configuration changed
*Feb 1 20:00:42.279: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/0) is up: new adjacency

10. EIGRP Packets
IP EIGRP relies on 5 types of packets to maintain its various tables and establish complex relationships with neighbor routers.
Packet Type
Description
Hello
Used to discover other EIGRP routers in the network.
Acknowledgement
Used to acknowledge the receipt of any EIGRP packet.
Update
Convey routing information to known destinations.
Query
Used to get specific information from a neighbor router.
Reply
Used to respond to a query.

11. EIGRP Hello Packets
Hello packets are used to discover & form adjacencies with neighbors.
Multicasted to:
IPv4:
IPv6: FF02::A
Hello packets are always sent unreliably.
Therefore Hello packets do not require acknowledgment.

12. EIGRP Neighbors
Amount of time since this neighbor was added to the neighbor table.
R2# show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(1)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
Se0/0/ :03:
Se0/0/ :13:
R2#
Neighbor’s IPv4 address
The local interface receiving EIGRP Hello packets.
Seconds remaining before declaring neighbor down.
Reset to hold time when Hello is received.

13. EIGRP Interfaces R2# show ip eigrp interfaces
EIGRP-IPv4 Interfaces for AS(1)
Xmit Queue PeerQ Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable Un/Reliable SRTT Un/Reliable Flow Timer Routes
Se0/0/ / / /
Se0/0/ / / /
Gi0/ / / /
R2#

14. EIGRP Interfaces R2# show ip eigrp interfaces detail
EIGRP-IPv4 Interfaces for AS(1)
Xmit Queue PeerQ Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable Un/Reliable SRTT Un/Reliable Flow Timer Routes
Se0/0/ / / /
Hello-interval is 5, Hold-time is 15
Split-horizon is enabled
Next xmit serial <none>
Packetized sent/expedited: 20/0
Hello's sent/expedited: 2186/4
Un/reliable mcasts: 0/0 Un/reliable ucasts: 23/23
Mcast exceptions: 0 CR packets: 0 ACKs suppressed: 0
Retransmissions sent: 0 Out-of-sequence rcvd: 1
Topology-ids on interface - 0
Authentication mode is not set
<rest of output omitted>
Expedited hellos are sent during initialization, startup
EIGRP uses small hello packets.
These are sent periodically approximately every 5 seconds on all kind of interfaces
except low-speed (T1 or slower) NBMA networks, where they are sent by default every
60 seconds. The time interval is called a hello timer.

15. IPv4 Routing Protocols R2# show ip protocols
*** IP Routing is NSF aware ***
Routing Protocol is "application"
Sending updates every 0 seconds
Invalid after 0 seconds, hold down 0, flushed after 0
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Maximum path: 32
Routing for Networks:
Routing Information Sources:
Gateway Distance Last Update
Distance: (default is 4)
<continued next slide>
Expedited hellos are sent during initialization, startup

16. IPv4 Routing Protocols EIGRP Process ID EIGRP Router ID
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-IPv4 Protocol for AS(1)
Metric weight K1=1, K2=0, K3=1, K4=0, K5=0
NSF-aware route hold timer is 240
Router-ID:
Topology : 0 (base)
Active Timer: 3 min
Distance: internal 90 external 170
Maximum path: 4
Maximum hopcount 100
Maximum metric variance 1
Automatic Summarization: disabled
Routing for Networks:
Routing Information Sources:
Gateway Distance Last Update
:23:27
:23:28
R2#
IPv4 Routing Protocols
EIGRP Process ID
EIGRP Router ID
Hopcount is not a metric
Variance – For unequal cost load balancing
Starting with 15.0 no auto-summary is the default
network statements
neighbors
Expedited hellos are sent during initialization, startup

17. IPv4 Routing Protocols EIGRP Composite Metric Formula
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-IPv4 Protocol for AS(1)
Metric weight K1=1, K2=0, K3=1, K4=0, K5=0
NSF-aware route hold timer is 240
Router-ID:
Topology : 0 (base)
Active Timer: 3 min
Distance: internal 90 external 170
Maximum path: 4
Maximum hopcount 100
Maximum metric variance 1
Automatic Summarization: disabled
Routing for Networks:
Routing Information Sources:
Gateway Distance Last Update
:23:27
:23:28
R2#
IPv4 Routing Protocols
EIGRP Composite Metric Formula
METRIC = ( [K1 x Bandwidth + (K2 x Bandwidth) / (256-load) + K3 x Delay] x [K5 / (Reliability + K4] ) x 256
METRIC = ( [1 x Bandwidth + (0 x Bandwidth) / (256-load) x Delay] x [0 / (Reliability + 0] ) x 256
METRIC = (1 x Bandwidth + 1 x Delay) x 256
NOTE:
The multiplication by 256 is a legacy feature to maintain backwards compatibility with IGRP.
Expedited hellos are sent during initialization, startup

18. EIGRP Wide Metrics
The EIGRP composite cost metric does not scale correctly for high-bandwidth interfaces or Ethernet channels, resulting in incorrect or inconsistent routing behavior.
The lowest delay that can be configured for an interface is 10 microseconds.
As a result, high-speed interfaces, such as 10 Gigabit Ethernet (GE) interfaces, or high-speed interfaces channeled together (GE ether channel) will appear to EIGRP as a single GE interface.
To resolve this issue, the EIGRP Wide Metrics feature supports 64-bit metric calculations
The 64-bit metric calculations work only in EIGRP named mode configurations.
The EIGRP Wide Metric is beyond the scope of this book.
For more information, see the Cisco.com document “EIGRP Wide Metrics,” at

19. Configuring Passive InterfacesX
R1(config)# router eigrp 1
R1(config-router)# passive-interface g0/0 X X
R2(config)# router eigrp 1
R2(config-router)# passive-interface g0/0
R3(config)# router eigrp 1
R3(config-router)# passive-interface g0/0

20. EIGRP Interfaces after Passive
R2# show ip eigrp interfaces
EIGRP-IPv4 Interfaces for AS(1)
Xmit Queue PeerQ Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable Un/Reliable SRTT Un/Reliable Flow Timer Routes
Se0/0/ / / /
Se0/0/ / / /
R2#
R2# show ip protocols
<selected output>
Routing Protocol is "eigrp 1”
Passive Interface(s):
GigabitEthernet0/0
Routing for Networks:

21. Observing Hello Packets
R1(config)# interface serial 0/0/0
R1(config-if)# no ip address
R1(config-if)#
*Feb 1 21:34:02.926: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/0) is down: interface down
R2# debug eigrp packets hello
(HELLO)
EIGRP Packet debugging is on
R2#
*Feb 1 21:28:40.602: EIGRP: Received HELLO on Se0/0/0 - paklen 20 nbr
*Feb 1 21:28:41.062: EIGRP: Sending HELLO on Se0/0/0 - paklen 20
*Feb 1 21:28:41.062: AS 1, Flags 0x0:(NULL), Seq 0/0 interfaceQ 0/0 iidbQ un/rely 0/0
*Feb 1 21:28:45.354: EIGRP: Sending HELLO on Se0/0/0 - paklen 20
*Feb 1 21:28:45.354: AS 1, Flags 0x0:(NULL), Seq 0/0 interfaceQ 0/0 iidbQ un/rely 0/0
*Feb 1 21:28:50.174: EIGRP: Sending HELLO on Se0/0/0 - paklen 20
*Feb 1 21:28:50.174: AS 1, Flags 0x0:(NULL), Seq 0/0 interfaceQ 0/0 iidbQ un/rely 0/0
*Feb 1 21:28:55.602: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/0) is down: holding time expired X
Shutdown on a serial link in a lab environment does not work because it brings down both ends of the link

22. EIGRP Neighbors w/ Differing Timers
5/15
5/15
R2# show ip eigrp interfaces detail serial 0/0/0
EIGRP-IPv4 Interfaces for AS(1)
Xmit Queue PeerQ Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable Un/Reliable SRTT Un/Reliable Flow Timer Routes
Se0/0/ / / /
Hello-interval is 5, Hold-time is 15
<>
R1# show ip eigrp interfaces detail serial 0/0/0
Se0/0/ / / /
R1#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(1)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
Se0/0/ :03:

23. EIGRP Neighbors w/ Differing Timers
5/15
10/30
R1(config)# interface serial 0/0/0
R1(config-if)# ip hello-interval eigrp 1 10
R1(config-if)# ip hold-time eigrp 1 30
R1(config-if)# end
R1#
R1# show ip eigrp interfaces detail serial 0/0/0
EIGRP-IPv4 Interfaces for AS(1)
Xmit Queue PeerQ Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable Un/Reliable SRTT Un/Reliable Flow Timer Routes
Se0/0/ / / /
Hello-interval is 10, Hold-time is 30
<>
R1# show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(1)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
Se0/0/ :25:

24. Initial Route Discovery
Process to establish and discover neighbor routes occurs simultaneously in EIGRP:
A new router (router A) comes up on the link and sends a hello packet through all of its EIGRP-configured interfaces.
Routers receiving the hello packet (router B) on one interface reply with update packets that contain all the routes they have in their routing tables, except those learned through that interface (split horizon). Router B sends an update packet to router A, but a neighbor relationship is not established until router B sends a hello packet to router A. The update packet from router B has the initialization bit set, indicating that this is the initialization process. The update packet includes information about the routes that the neighbor (router B) is aware of, including the metric that the neighbor is advertising for each destination.
After both routers have exchanged hellos, and the neighbor adjacency is established, router A replies to router B with an ACK packet, indicating that it received the update information.
Router A assimilates all update packets in its topology table. The topology table includes all destinations advertised by neighboring (adjacent) routers. It lists each destination, all the neighbors that can reach the destination, and their associated metric.
Router A then sends an update packet to router B.
Upon receiving the update packet, router B sends an ACK packet to router A.
After router A and router B successfully receive the update packets from each other, they are ready to update their routing tables with the successor routes from the topology table.

25. Observing EIGRP R3# debug eigrp packet R3# conf t
R3(config)# router eigrp 1
R3(config-router)# network
*Feb 1 22:06:45.678: EIGRP: Sending HELLO on Se0/0/1 - paklen 20
*Feb 1 22:06:45.698: EIGRP: Received HELLO on Se0/0/1 - paklen 30 nbr
*Feb 1 22:06:45.698: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/1) is up: new adjacency
*Feb 1 22:06:45.698: *Feb 1 22:06:45.698: EIGRP: Enqueueing UPDATE on Se0/0/1 - paklen 0 nbr tid 0 iidbQ un/rely 0/1 peerQ un/rely 0/0
*Feb 1 22:06:45.706: EIGRP: Sending UPDATE on Se0/0/1 - paklen 0 nbr tid 0
*Feb 1 22:06:45.706: AS 1, Flags 0x1:(INIT), Seq 63/0 interfaceQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
*Feb 1 22:06:47.770: EIGRP: Received UPDATE on Se0/0/1 - paklen 222 nbr
*Feb 1 22:06:47.770: AS 1, Flags 0x0:(NULL), Seq 64/63 interfaceQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
*Feb 1 22:06:47.770: EIGRP: Enqueueing ACK on Se0/0/1 - paklen 0 nbr tid 0
*Feb 1 22:06:47.770: Ack seq 64 iidbQ un/rely 0/0 peerQ un/rely 1/1
*Feb 1 22:06:47.774: EIGRP: Sending ACK on Se0/0/1 - paklen 0 nbr tid 0
*Feb 1 22:06:47.774: AS 1, Flags 0x0:(NULL), Seq 0/64 interfaceQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 1/1
*Feb 1 22:06:47.778: EIGRP: Received ACK on Se0/0/1 - paklen 0 nbr
*Feb 1 22:06:47.778: AS 1, Flags 0x0:(NULL), Seq 0/64 interfaceQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1

26. Observing EIGRP R3# show ip eigrp traffic
EIGRP-IPv4 Traffic Statistics for AS(1)
Hellos sent/received: 8319/6103
Updates sent/received: 48/43
Queries sent/received: 5/9
Replies sent/received: 9/5
Acks sent/received: 51/57
SIA-Queries sent/received: 0/0
SIA-Replies sent/received: 0/0
Hello Process ID: 145
PDM Process ID: 106
Socket Queue: 0/10000/2/0 (current/max/highest/drops)
Input Queue: 0/2000/2/0 (current/max/highest/drops)
R3#

27. IPv4 Routing Table – EIGRP Routes The EIGRP World from R2’s Distance Vector Perspective
R2# show ip route eigrp
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
<output omitted>
Gateway of last resort is not set
/8 is variably subnetted, 5 subnets, 2 masks
D /29 [90/ ] via , 00:58:05, Serial0/0/1
/16 is variably subnetted, 4 subnets, 2 masks
D /24 [90/ ] via , 00:58:05, Serial0/0/1
D /24 [90/ ] via , 00:58:05, Serial0/0/1
R2#

28. 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
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

31. I can get to 10.0.0.0/8 with a metric of 300. 10.0.0.0/8 RX R2 R3
I will choose R3 to get to /8 which means I have a cost of 120. Is R2 a valid back up? RA R1 RB
No, because it comes back through me R1 (loop). It only knows this route because of me.

32. I can get to 10.0.0.0/8 with a metric of 300. RX RB R2 R3
I will choose R3 to get to /8 which means I have a cost of 120. Is R2 a valid back up? RA R1
Yes, because it has its own path to /8. (no loop)

33. I can only use R2 as a backup if it reports a cost less than my total cost through R3.
EIGRP is a distance vector routing protocol.
Does not see any topology map.
Can’t tell if there is a loop or not?
To play it safe, EIGRP only accepts a backup route if it meets the Feasibility Condition (coming).
R1 will only use R2 if R2’s metric to /8 is less than R1’s cost through R3.

34. R2’s EIGRP Topology Table
R2# show ip eigrp topology
EIGRP-IPv4 Topology Table for AS(1)/ID( )
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P /29, 1 successors, FD is
via Connected, Serial0/0/0
P /24, 1 successors, FD is 28160
via Connected, GigabitEthernet0/0
P /29, 1 successors, FD is
via ( / ), Serial0/0/1
via ( / ), Serial0/0/0
P /24, 1 successors, FD is
via ( /28160), Serial0/0/1
via ( / ), Serial0/0/0
P /29, 1 successors, FD is
via Connected, Serial0/0/1
P /24, 1 successors, FD is
via ( / ), Serial0/0/1
via ( /28160), Serial0/0/0
R2#

35. The Successor R2# show ip eigrp topology
P /24, 1 successors, FD is
via ( /28160), Serial0/0/1
via ( / ), Serial0/0/0
R3: Successor
Outbound interface to reach this network
Feasible distance
Next hop address of the successor
Successor’s (R3’s)
Reported Distance
Successor

36. The Feasible Successor
The reported distance - EIGRP neighbor’s FD to the same destination network.
The metric that a router reports to a neighbor about its own cost to that network.
Feasibility Condition: The FC is met when a neighbor’s reported distance (RD) to a network is less than the local router’s FD to the same destination network.
R2# show ip eigrp topology
P /24, 1 successors, FD is
via ( /28160), Serial0/0/1
via ( / ), Serial0/0/0
R1: Feasible Successor
Outbound interface to reach this network
R2’s feasible distance if R1 becomes the Successor.
This would the metric in R2’s routing table via R1.
R1’s (feasible successor)
Reported Distance to R2
Next hop address of the Feasible Successor
Feasible Successor

37. Why is R1 a Feasible Successor?
R2# show ip eigrp topology
P /24, 1 successors, FD is
via ( /28160), Serial0/0/1
via ( / ), Serial0/0/0
R3: Successor
R1: Feasible Successor
Feasibility Condition:
R1’s Reported Distance is less than R2’s Feasible Distance via R3, so R1 is a Feasible Successor.
A Feasible Successor is a neighbor who has a loop-free backup path to the same network as the successor by satisfying the feasibility condition.
Can become new successor with no packets lost.
Feasible Successor

38. Why is R1 a Feasible Successor?
R2# show ip eigrp topology
P /24, 1 successors, FD is
via ( /28160), Serial0/0/1
via ( / ), Serial0/0/0
R3: Successor
R1: Feasible Successor
My current metric (feasible distance) 3,014,400. If current best path to becomes unavailable you will become my successor with a (feasible distance) of 41,026,560 (slower bw and additional delay)
My cost to is 2,172,416. If this is less than your current metric (feasible distance) then I am a feasible successor.
Successor
Feasible Successor

39. Using a Feasible Successor?
My new successor is R1 with a metric (feasible distance) of 41,026,560 X
I’m the new successor
R2(config)# interface serial 0/0/1
R2(config-if)# shutdown
R2(config-if)# end
*Feb 1 23:51:54.218: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/1) is down: interface down
R2# show ip eigrp topology
<>
P /24, 1 successors, FD is
via ( / ), Serial0/0/0
R2# show ip route eigrp
D /24 [90/ ] via , 00:00:22, Serial0/0/0
R2#
R2 immediately uses Feasible Successor from EIGRP Topology Table

40. Back to normal Feasible Successor Successor
R2(config)# interface serial 0/0/1
R2(config-if)# no shutdown
R2(config-if)# end
*Feb 2 00:02:59.422: %LINK-3-UPDOWN: Interface Serial0/0/1, changed state to up
*Feb 2 00:03:03.346: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/1) is up: new adjacency
R2# show ip route eigrp
<>
D /24 [90/ ] via , 00:00:09, Serial0/0/1
R2#

41. IPv4 Routing Table – EIGRP Routes The EIGRP World from R1’s Distance Vector Perspective
R1# show ip route eigrp
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
<output omitted>
Gateway of last resort is not set
/8 is variably subnetted, 5 subnets, 2 masks
D /29 [90/ ] via , 00:07:11, Serial0/0/1
/16 is variably subnetted, 4 subnets, 2 masks
D /24 [90/ ] via , 00:07:09, Serial0/0/1
D /24 [90/ ] via , 00:07:09, Serial0/0/1
R1#

42. R1’s EIGRP Topology Table
R1# show ip eigrp topology
EIGRP-IPv4 Topology Table for AS(1)/ID( )
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P /29, 1 successors, FD is
via Connected, Serial0/0/0
P /24, 1 successors, FD is
via ( / ), Serial0/0/1
via ( /28160), Serial0/0/0
P /29, 1 successors, FD is
via Connected, Serial0/0/1
P /24, 1 successors, FD is
via ( /28160), Serial0/0/1
P /29, 1 successors, FD is
via ( / ), Serial0/0/1
via ( / ), Serial0/0/0
P /24, 1 successors, FD is 28160
via Connected, GigabitEthernet0/0
R1#

43. The Successor R1# show ip eigrp topology
P /24, 1 successors, FD is
via ( /28160), Serial0/0/1
R3: Successor
Outbound interface to reach this network
Feasible distance
Next hop address of the successor
Successor’s (R3’s)
Reported Distance
NO feasible successor
To be a feasible successor, R2 must satisfy the Feasibility Condition.

44. Why is R2 is NOT a Feasible Successor?
R1# show ip eigrp topology all-links
P /24, 1 successors, FD is , serno 23
via ( /28160), Serial0/0/1
via ( / ), Serial0/0/0
R3: Successor
R2: NOT Feasible Successor
Feasibility Condition:
R2’s Reported Distance is NOT less than R1’s Feasible Distance via R3, so R2 is NOT a Feasible Successor.
Does this mean R2 cannot be used if the current best path fails?
No, R2 can be used, but there will be a longer delay before adding it to the routing table.
DUAL will need to find (Query) R2 to see if it has a route.

45. DUAL: An Introduction
R2 sends updates out all interfaces
Not shown X

46. Observing EIGRP X Reply Query Query Reply R1# debug eigrp fsm
EIGRP Finite State Machine debugging is on
R1# conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)# interface serial 0/0/1
R1(config-if)# shutdown
*Feb 2 00:38:10.082: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/1) is down: interface down
*Feb 2 00:38:10.086: DUAL: Destination /24 for tid 0
*Feb 2 00:38:10.086: EIGRP-IPv4(1): Find FS for dest /24. FD is , RD is on tid 0
*Feb 2 00:38:10.086: DUAL: AS(1) Dest /24 entering active state for tid 0.
*Feb 2 00:38:10.086: EIGRP-IPv4(1): Set reply-status table. Count is 1.
*Feb 2 00:38:10.554: DUAL: AS(1) Removing dest /24, nexthop
*Feb 2 00:38:10.554: EIGRP-IPv4(1): rcvreply: /24 via metric / for tid
*Feb 2 00:38:10.554: EIGRP-IPv4(1): Find FS for dest /24. FD is , RD is on tid 0found
*Feb 2 00:38:10.554: DUAL: AS(1) RT installed /24 via
*Feb 2 00:38:10.554: DUAL: AS(1) Send update about /24. Reason: metric chg on tid 0
Query
Reply X
Neighbor change
Find FS for – There isn’t one
DUAL enters active state
Set reply status – R1 Sends Query
Removes current route via R3 from routing table
DUAL receives a Reply from R2 with metric and RD or
See if there is a FS for this (no one responds – none)
Remove R3 as successor from topology table
R1 is new successor and route is installed.
Send routing update to any neighbors about new route to

47. New Route X I’m the new successor
My new successor is R2 with a metric (feasible distance) of 41,026,560. I don’t have a feasible successor. X
R1# show ip eigrp topology
<>
P /24, 1 successors, FD is
via ( / ), Serial0/0/0
R1#
R1# show ip route eigrp
D /24 [90/ ] via , 00:14:08, Serial0/0/0 R1

48. Back to normal R1(config)# interface serial 0/0/1
R1(config-if)# no shutdown
R1(config-if)# end
*Feb 2 01:08:40.865: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor (Serial0/0/1) is up: new adjacency
R1#
R1# show ip eigrp topology
<>
P /24, 1 successors, FD is
R1# via ( /28160), Serial0/0/1
R1# show ip route eigrp
D /24 [90/ ] via , 00:00:13, Serial0/0/1 48

49. EIGRP Queries, Stub Routing, Summarization

50. X X EIGRP Queries Queries Replies
Router B
Queries
Replies
Router A X X
When there is no feasible successor DUAL puts the route into Active (topology table) and sends queries to neighbors looking for another path.

51. EIGRP Queries and Stuck in Active
Router loses a route and does not have an FS in its topology table, it looks for an alternative path to the destination. - known as going active on a route
If a neighbor does not have an alternative route, it queries each of its own neighbors for an alternative path.
The queries then propagate through the network, thus creating an expanding tree of queries.

52. X X X Stuck in Active (SIA) Queries Replies SIA
Router C
Stuck in Active (SIA)
Router D X
Router B
Queries
Replies
SIA
Router A X X
When EIGRP returns a stuck in active (SIA) message, it means that it has not received a reply to a query.
Summarization can help prevent SIA.

53. Stuck-in-Active EIGRP 101 EIGRP 102
The most common reasons for SIA routes are as follows:
The router is too busy to answer the query
The link between the two routers is not good
A failure causes traffic on a link to flow in only one direction.
This is called a unidirectional link.
Misconceptions
Using multiple EIGRP domains (AS’s) to simulate OSPF areas (later) will help limit the scope of the queries.
This is not true, the boundary router will create a new EIGRP query into the other EIGRP domain.

54. Queries Optimizing EIGRP Reduce queries EIGRP Summarization
EIGRP Stub Routing
Reduce the affect of SIAs
EIGRP Active Enhancement Process

55. Reduce Queries by using Summary Routes
HQ(config)# interface serial 0/0/0
HQ(config-if)# ip summary-address eigrp
HQ performs summarization for all remote networks.
A summary route is announced to other routers, like router GW.

56. Reduce Queries by using Summary Routes?
Connectivity to the remote location fails
HQ has no feasible successors to reach the lost network
HQ sends a query to its neighbors including GW.
GW receives a query for a network /24…
Immediately responds with a reply message without further forwarding the query because it has a summary route /16 from HQ, which also describes /24 prefix.
Because this route was learned from router HQ, router GW will respond that it does not have an alternative path for /24.
The summary is still valid as long as there is one prefix covered by the summary.

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

58. Manual Summarization
/24, /24, /24
/24, /24, /24
Only pertinent routes shown
R1# show ip route
D /24 [90/ ] via , 02:07:38, S0/0/1
D /24 [90/ ] via , 00:00:34, S0/0/1
D /24 [90/ ] via , 00:00:18, S0/0/1
R2# show ip route
D /24 [90/ ] via , 02:08:50, S0/0/1
D /24 [90/ ] via , 00:01:46, S0/0/1
D /24 [90/ ] via , 00:01:30, S0/0/1
R1 and R2 routing tables show these additional networks in their routing tables.
Instead of sending three separate networks, R3 can summarize the /24, /24, and /24 networks as a single route.
Instead of sending three separate networks, R3 can summarize the /24, /24, and /24 networks as a single route.

59. 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
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 /22
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
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 /22

60. Configure EIGRP Manual Summarization
/22
/22
Router(config-if)# ip summary-address eigrp as-number network-address subnet-mask
R3(config)# interface serial 0/0/0
R3(config-if)# ip summary-address eigrp
R3(config)# interface serial 0/0/1
R3# show ip route
<output omitted>
D /22 is a summary, 00:00:06, Null0
Creates a Null0 summary route
Because R3 has two EIGRP neighbors, the EIGRP manual summarization in configured on both Serial 0/0/0 and Serial 0/0/1.

61. Verify EIGRP Manual Summarization
/22
/22
R1# show ip route
<output omitted>
D /22 [90/ ] via , 00:01:11, Serial0/0/1
R2# show ip route
D /22 [90/ ] via , 00:00:23, Serial0/0/1
Fewer number of total routes in routing table - Faster routing table lookup process.
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.
Summary routes lessen the number of total routes in routing tables, which makes the routing table lookup process more efficient.
Summary routes also require less bandwidth utilization for the routing updates because a single route can be sent rather than multiple individual routes.

62. I’m an EIGRP for IPv4 router configured for automatic summarization.
Automatic Summarization at Classful Network Boundary
I’m an EIGRP for IPv4 router configured for automatic summarization.
IPv4 Routing Table
/24
/24
/24
/30 R1 R2
/16 via R1
Summary Update: /16
Classful Networks
Class A: to Default Mask: or /8
Class B: to Default Mask: or /16
Class C: to Default Mask: or /24
When enabled, EIGRP summarizes at classful boundaries.
EIGRP groups subnets into their Class A, B, or C network address and creates a single entry.
Media Description:
Use graphic from powerpoint

63. EIGRP for IPv4 automatic summarization defaults
Since IOS 15.0(1)M and 12.2(33), automatic summarization is disabled.
R1(config-router)# no auto-summary
Prior, automatic summarization was enabled.
R1(config-router)# auto-summary
/24
/24
/24
/24
/24
/24
R3# show ip route eigrp
<Output omitted>
/16 is variably subnetted, 3 subnets, 2 masks
D /24 [90/ ] via , 02:21:10, Serial0/0/0
D /24 [90/ ] via , 02:21:10, Serial0/0/1
D /30 [90/ ] via , 02:21:10, Serial0/0/1
[90/ ] via , 02:21:10, Serial0/0/0
R3#

64. Propagating a Default Route
Default Static Route
Propagating a Default Route
Redistribute static
Redistribute static
R2(config)# ip route serial 0/1/0
R2(config)# router eigrp 1
R2(config-router)# redistribute static
Better
R2(config)# ip route serial 0/1/0
R2(config)# interface serial 0/0/0
R2(config-if)# ip summary-address eigrp
R2(config)# interface serial 0/0/1

65. Queries Optimizing EIGRP Reduce queries EIGRP Summarization
EIGRP Stub Routing
Reduce the affect of SIAs
EIGRP Active Enhancement Process

66. EIGRP Interfaces
The summary route of /23 is installed in HQ’s route table rather than the specific (directly connected) network /24 because /24 is included in the summary.
HQ# show ip route eigrp
D /24 [90/409600] via , 00:12:07, Ethernet0/0
D /23 [90/307200] via , 00:12:07, Ethernet0/0
D EX /24 [170/307200] via , 00:12:07, Ethernet0/0
BR1A announces to HQ:
Summary route to /23 ( /24 and  /24)
It’s static route to /24 that it redistributes into EIGRP and announces the prefix as an external EIGRP route to HQ.
BR1A also advertises its own directly connected networks /24 and /24

67. Stub Routers X X Stub Queries
EIGRP Updates X X
Stub
Queries
Stub Routers learn routes from nonstub routers but…
Stub routers do not forward EIGRP learned routes to other neighbors
Nonstub routers do not send query messages to stub routers…. Stub will send what it wants (if anything).

68. Stub Router Options Options – One or more, except for receive-only
connected – Sends connected routes covered by a network statement.
Most widely practical stub option (default)
summary - Sends summary routes, manually created or automatic. (default)
static - Sends static routes redistributed with the redistribute static command.
redistributed – Sends all redistributed routes configured with the redistribute command.
receive-only - Restricts the stub router from sharing any of its routes with any other EIGRP router.
This option does not permit any other option to be used.
This option is rarely used.
Router has a single interface or using NAT (later)
EIGRP Updates
Note: There is one more keyword the leak-map option. The leak-map keyword permits the EIGRP stub routing feature to reference a leak map that identifies routes that are allowed to be advertised on an EIGRP stub router that would normally have been suppressed.

69. Stub default: connected and summary
BR1A(config)# router eigrp 1
BR1A(config-router)# eigrp stub
*Oct 18 11:51:16.232: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor
(Ethernet0/0) is down:
HQ# show ip route eigrp
D /24 [90/409600] via , 00:09:07, Ethernet0/0
D /23 [90/307200] via , 00:09:07, Ethernet0/0
Default: connected and summary
When you configure or change the EIGRP stub options, any neighboring session needs to be torn down and reestablished.

70. Stub default: connected and summary
BR1A(config)# router eigrp 1
BR1A(config-router)# eigrp stub
HQ# show ip eigrp neighbors detail
EIGRP-IPv4 Neighbors for AS(100)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
Se0/0/ :21:
Version 16.0/2.0, Retrans: 0, Retries: 0, Prefixes: 3
Topology-ids from peer - 0
Stub Peer Advertising (CONNECTED SUMMARY ) Routes
Suppressing queries
Max Nbrs: 0, Current Nbrs: 0
HQ#
Default: connected and summary

71. Stub default: connected
BR1A(config)# router eigrp 1
BR1A(config-router)# eigrp stub connected
HQ# show ip route eigrp
D /24 [90/409600] via , 00:14:52, Ethernet0/0
D /24 [90/307200] via , 00:14:52, Ethernet0/0
connected – Sends connected routes covered by a network statement.
Most widely practical stub option (default)

72. Stub default: receive-only
BR1A(config)# router eigrp 1
BR1A(config-router)# eigrp stub receive-only
HQ# show ip route eigrp
<No routes learned from BR1A>
receive-only - Restricts the stub router from sharing any of its routes with any other EIGRP router.
Useful in cases when all hosts behind router BR1A would be translated using NAT with PAT.
HQ has no need to be aware of networks behind router BR1A because all outgoing traffic would be destined for BR1A’s egress interface, where NAT would be performed.

73. Queries Optimizing EIGRP Reduce queries EIGRP Summarization
EIGRP Stub Routing
Reduce the affect of SIAs
EIGRP Active Enhancement Process

74. Active Process Enhancement feature
Cisco IOS Software Release 12.1(5) and later, with the Active Process Enhancement feature.
This feature enables an EIGRP router to monitor the progression of the search for a successor route and ensure that the neighbor is still reachable.

75. X X BEFORE Active Process Enhancement feature. 10.1.1.0/24 gone; no FS
Never heard from B
So after 3 min reset adjacency along with all networks X
Query
3 min timer
/24 gone; no FS B
No entry so sends Query
Bad link; reply never makes it
No entry send Reply C
/24 gone;
Remove /24

76. X AFTER Active Process Enhancement feature.
Thanks for letting me know,
I will not terminate our adjacency.
/24 gone; no FS A
Query
The neighbor relationship between Routers A and B remains intact.
After 1.5 min SIA Query
/24 gone; no FS
SIA Reply: I’m ok but waiting on C B
No entry so sends Query
After 1.5 min SIA Query
(3 attempts until I terminal
adjacency with C)
Bad link; reply never makes it
No entry send Reply C
/24 gone;
Remove /24

77. EIGRP Load Balancing

78. Variance command Router(config)# router eigrp 1
Router(config-router)# variance multiplier
Cisco IOS allows up to 32 equal-cost paths (IOS dependent), 4 by default.
EIGRP does unequal cost load balancing, forwarding packets relative to the metric.
The variance command:
Instructs the router to include routes with a metric less than or equal to n times the minimum metric route for that destination
n is the number specified by the variance command (1 -128).
Default = 1
The maximum-paths number EIGRP is used to sent the number of load-balancing paths (up to 32 paths).
1 disables load balancing
Note: If a path isn't a feasible successor, then it isn't used in load balancing.
Note: Load balancing is only performed on traffic that passes through the router, not traffic generated by the router.

79. Variance command Successor: R3 with a FD of 20RD FS
Succ FS
Successor: R3 with a FD of 20
Feasible Successors: R2 and R5
R2’s RD of 10 < R3’s FD of 20
R5’s RD of 10 < R3’s FD of 20
R4 is NOT a FS because it’s RD of 25 > R3’s FD of 20

80. Variance command RD FS Succ x 2 = 40 R1(config)# router eigrp 110 FS
R1(config-router)# variance 2
Variance = 2
R3’s FDv 2 x 20 (FD) = 40
R2 is added as successor to R1’s routing table: R2’s FD of 30 < R3’s FDv of 40
R5 is NOT added to R1’s routing table: R5’s FD of 50 > R3’s FDv of 40
R5 would still be a Feasible Successor
Note: R4 is not considered even if it’s FD was < or = R3’s FDv of 40 because it is not a FS
The load in is balanced proportional to the bandwidth.
FD of the route via router R2 is 30
FD of the route via router R3 is 20
Ratio of traffic between the two paths will be proportional to the metric.

81. EIGRP over MPLS

82. Layer 2 and Layer 3 MPLS VPN Solutions
Layer 2 MPLS VPN provides a Layer 2 service across the backbone
R1 and R2 are connected together on the same IP subnet.
Layer 3 MPLS VPN provides a Layer 3 service across the backbone
R1 and R2 are connected to ISP edge routers; on each side, a separate IP subnet is used.

83. Layer 3 MPLS VPNs L3
/30
network
/30
network
R1 and R2 are configured for EIGRP as if there were a corporate core network between them.
EIGRP parameters between R1 and R2 (such as the AS number, authentication password, and so on) are often governed/coordinated by the service provider.

84. Layer 3 MPLS VPNs
R1 establishes an EIGRP neighbor relationship with the PE1 (Provider Edge) router,
R2 establishes an EIGRP neighbor relationship with the PE2 router.
Routers R1 and R2 do NOT establish an EIGRP neighbor relationship with each other.

85. Layer 2 MPLS VPNs
/27
network
EIGRP needs to be enabled with the same AS number on both routers.
network command includes the interface toward the PE router (PE1 and PE2) over which the routers R1 and R2 will form their neighbor relationship.
From the EIGRP perspective, the MPLS backbone and routers PE1 and PE2 are not visible.

86. Layer 2 MPLS VPNs
A neighbor relationship is established directly between routers R1 and R2 over the MPLS backbone.

87. EIGRP for IPv6 Separate Presentation
Can be found on my CIS 185 ROUTE course materials page or by going to:

88. CIS 185 CCNP ROUTE Chapter 2: Implementing EIGRP
Rick Graziani
Cabrillo College