2.1.2 Lab – Implement EIGRP for IPv4 Answers

• Recommend

Lab – Implement EIGRP for IPv4 (Answers Version)

Answers Note: Red font color or gray highlights indicate text that appears in the instructor copy only.

Topology

Addressing Table

Objectives

Part 1: Build the Network and Configure Basic Device Settings

Part 2: Configure and Verify EIGRP for IPv4

Part 3: Tune EIGRP for IPv4

Background / Scenario

EIGRP is an interior gateway routing protocol created by Cisco and published as open source in 2016 in RFC 7868. It is a very efficient distance-vector based protocol. In this lab, you will configure and examine EIGRP in two forms, Classic EIGRP and Named EIGRP. Named EIGRP is an update to Classic EIGRP that added multiprotocol support and default support for wide metrics.

Note: This lab is an exercise in configuring options available for EIGRP supporting IPv4 and does not necessarily reflect implementation best practices.

Note: The routers used with CCNP hands-on labs are Cisco 4221 with Cisco IOS XE Release 16.9.4 (universalk9 image). The switches used in the labs are Cisco Catalyst 3650 with Cisco IOS XE Release 16.9.4 (universalk9 image). Other routers, switches, and Cisco IOS versions can be used. Depending on the model and Cisco IOS version, the commands available and the output produced might vary from what is shown in the labs. Refer to the Router Interface Summary Table at the end of the lab for the correct interface identifiers.

Note: Make sure that the routers and switches have been erased and have no startup configurations. If you are unsure, contact your instructor.

Answers Note: Refer to the Answers Lab Manual for the procedures to initialize and reload devices.

Required Resources

• 3 Routers (Cisco 4221 with Cisco IOS XE Release 16.9.4 universal image or comparable)
• 2 Switches (Cisco 3650 with Cisco IOS XE Release 16.9.4 universal image or comparable)
• 1 PC (Choice of operating system with a terminal emulation program installed)
• Console cables to configure the Cisco IOS devices via the console ports
• Ethernet cables as shown in the topology

Part 1:Build the Network and Configure Basic Device Settings

In Part 1, you will set up the network topology and configure basic settings on routers.

Step 1:Cable the network as shown in the topology.

Attach the devices as shown in the topology diagram, and cable as necessary.

Step 2:Configure basic settings for each device.

1. Console into each device, enter global configuration mode, and apply the basic settings. The startup configurations for each device are provided below.

Open configuration window

Router R1

hostname R1

no ip domain lookup

banner motd # R1, Implement EIGRP for IPv4 #

line con 0

exec-timeout 0 0

logging synchronous

exit

line vty 0 4

privilege level 15

exec-timeout 0 0

password cisco123

login

exit

interface g0/0/1

no ip address

no shutdown

exit

interface g0/0/1.1

encapsulation dot1q 1

ip address 172.16.1.1 255.255.255.0

no shutdown

exit

interface g0/0/1.2

encapsulation dot1q 2

ip address 192.168.1.1 255.255.255.0

no shutdown

exit

interface g0/0/0

ip address 10.0.12.1 255.255.255.0

no shutdown

exit

ip dhcp pool HOSTS

network 192.168.1.0 255.255.255.0

default-router 192.168.1.1

exit

end

Router R2

hostname R2

no ip domain lookup

banner motd # R2, Implement EIGRP for IPv4 #

line con 0

exec-timeout 0 0

logging synchronous

exit

line vty 0 4

privilege level 15

exec-timeout 0 0

password cisco123

login

exit

interface g0/0/0

ip address 10.0.12.2 255.255.255.0

no shutdown

exit

interface g0/0/1

ip address 10.0.23.2 255.255.255.0

no shutdown

exit

end

Router R3

hostname R3

no ip domain lookup

banner motd # R3, Implement EIGRP for IPv4 #

line con 0

exec-timeout 0 0

logging synchronous

exit

line vty 0 4

privilege level 15

exec-timeout 0 0

password cisco123

login

exit

interface g0/0/0

ip address 10.0.23.3 255.255.255.0

no shutdown

exit

interface g0/0/1

ip address 172.16.13.1 255.255.255.0

no shutdown

exit

interface loopback 0

ip address 192.168.3.1 255.255.255.0

no shutdown

exit

end

Switch D1

hostname D1

no ip domain lookup

banner motd # D1, Implement EIGRP for IPv4 #

line con 0

exec-timeout 0 0

logging synchronous

exit

line vty 0 4

privilege level 15

exec-timeout 0 0

password cisco123

login

exit

vlan 2

name HOST-VLAN

exit

interface range g1/0/1 – 24, g1/1/1 – 4

shutdown

exit

interface g1/0/1

switchport mode access

spanning-tree portfast

no shutdown

exit

interface g1/0/11

switchport mode trunk

no shutdown

exit

interface g1/0/23

switchport mode access

switchport access vlan 2

spanning-tree portfast

no shutdown

exit

end

Switch D2

hostname D2

no ip domain lookup

ip routing

banner motd # D2, Implement EIGRP for IPv4 #

line con 0

exec-timeout 0 0

logging synchronous

exit

line vty 0 4

privilege level 15

exec-timeout 0 0

password cisco123

login

exit

interface range g1/0/1 – 24, g1/1/1 – 4

shutdown

exit

interface g1/0/1

no switchport

ip address 172.16.1.2 255.255.255.0

no shutdown

exit

interface g1/0/11

no switchport

ip address 172.16.13.2 255.255.255.0

no shutdown

exit

end

2. Set the clock on each device to UTC time.
3. Save the running configuration to startup-config.

Close configuration window

4. Verify that PC1 receives an address via DHCP.
5. Verify that PC1 can ping its default gateway.

Part 2:Configure and Verify EIGRP for IPv4

In this part of the lab, you will configure and verify EIGRP in the network. R1 and R3 will used Named EIGRP, while R2 will use Classic EIGRP. After you have established the network, you will examine the differences in how each version of EIGRP deals with metrics.

For the lab, you will use the Autonomous System number 27 on all routers.

Step 1:Configure Classic EIGRP for IPv4 on R2.

1. Start the configuration of Classic EIGRP by issuing the router eigrp 27 command.

Open configuration window

R2(config)# router eigrp 27

2. Configure the EIGRP router ID using the eigrp router-id command. Use the number 2.2.2.2 for R2.

R2(config-router)# eigrp router-id 2.2.2.2

3. Identify the interfaces that should be speaking EIGRP and the networks that should be included in the EIGRP topology table. This is done with the network command.

It is best to be as specific as possible when creating network statements, while balancing efficiency and the number of commands necessary. For our lab example, we will use network 10.0.0.0 255.255.224.0 to specify the interfaces. This covers less network space than 10.0.0.0/8, while including both interfaces with a single network command.

R2(config-router)# network 10.0.0.0 255.255.224.0

R2(config-router)# end

4. Verify the interfaces now involved in EIGRP with the show ip eigrp interfaces command.

R2# show ip eigrp interfaces

EIGRP-IPv4 Interfaces for AS(27)

Xmit QueuePeerQMeanPacing TimeMulticastPending

InterfacePeersUn/ReliableUn/ReliableSRTTUn/ReliableFlow TimerRoutes

Gi0/0/000/00/000/0 00

Gi0/0/100/00/000/0 00

Close configuration window

Step 2:Configure Named EIGRP for IPv4 on R1 and R3.

1. Start the configuration of Named EIGRP by issuing the router eigrp [ name ] command. The name parameter can be a number, but the number does not identify an Autonomous System as it does with Classic EIGRP, it simply identifies the process. For our purposes, name the process BASIC-EIGRP-LAB.

Open configuration window

R1(config)# router eigrp BASIC-EIGRP-LAB

2. Enter into address-family configuration mode with the address-family ipv4 unicast autonomous-system 27 command.

R1(config-router)# address-family ipv4 unicast autonomous-system 27

3. Configure the EIGRP router ID using the eigrp router-id command. Use the number 1.1.1.1 for R1.

R1(config-router-af)# eigrp router-id 1.1.1.1

4. Identify the interfaces that should be speaking EIGRP and the networks that should be included in the EIGRP topology table. This is done with the network command. In this case, the configuration requires three network commands. An example for R1 follows:

R1(config-router-af)# network 10.0.12.0 255.255.255.0

R1(config-router-af)# network 172.16.1.0 255.255.255.0

R1(config-router-af)# network 192.168.1.0 255.255.255.0

R1(config-router-af)# end

Close configuration window

5. Repeat Steps 2a through 2d for R3 and D2. Use 3.3.3.3 for the router ID on R3, and 132.132.132.132 for the router ID on D2. Configure the appropriate network statements on both devices according to the Addressing Table.

Open configuration window

R3(config)# router eigrp BASIC-EIGRP-LAB

R3(config-router)# address-family ipv4 unicast autonomous-system 27

R3(config-router-af)# eigrp router-id 3.3.3.3

R3(config-router-af)# network 10.0.23.0 255.255.255.0

R3(config-router-af)# network 172.16.13.0 255.255.255.0

R3(config-router-af)# network 192.168.3.0 255.255.255.0

R3(config-router-af)# end

Close configuration window

Open configuration window

D2(config-if)# router eigrp BASIC-EIGRP-LAB

D2(config-router)# address-family ipv4 unicast autonomous-system 27

D2(config-router-af)# eigrp router-id 132.132.132.132

D2(config-router-af)# network 172.16.0.0 255.255.0.0

D2(config-router-af)# end

Close configuration window

Step 3:Verify EIGRP for IPv4.

1. A few seconds after configuring the network statements, you should have seen syslog messages noting that EIGRP adjacencies have been formed.

*Feb 18 15:49:34.243: %DUAL-5-NBRCHANGE: EIGRP-IPv4 27: Neighbor 10.0.12.2 (GigabitEthernet0/0/0) is up: new adjacency

2. To verify that routing is working, ping from PC1 to interface Loopback 0 on R3 (192.168.3.1). The ping should be successful. You can also randomly ping other addresses in the topology.
3. On R1, examine the EIGRP entries in the IP routing table using the show ip route eigrp | begin Gateway command. As you can see, there is one path installed in the routing table for the network, and two paths for the 192.168.3.0/24 network. Take note of the metric values listed.

Open configuration window

R1# show ip route eigrp | begin Gateway

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks

D10.0.23.0/24 [90/15360] via 10.0.12.2, 00:00:12, GigabitEthernet0/0/0

172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks

D172.16.13.0/24

[90/15360] via 172.16.1.2, 00:00:12, GigabitEthernet0/0/1.1

D192.168.3.0/24

[90/16000] via 172.16.1.2, 00:00:12, GigabitEthernet0/0/1.1

[90/16000] via 10.0.12.2, 00:00:12, GigabitEthernet0/0/0

4. Now examine the EIGRP topology table using the show ip eigrp topology all-links command. The all-links parameter instructs the router to display all available routes, including the ones that are not successors or feasible successors.

Remember that the topology table is EIGRP’s database of route information. EIGRP selects the best paths from this database, based on the DUAL algorithm, and offers them to the IP routing table. However, the IP routing table does not have to use those offered paths, because the router may have learned about the same network from a more reliable routing source, which would be a routing source with a lower administrative distance.

R1# show ip eigrp topology all-links

EIGRP-IPv4 VR(BASIC-EIGRP-LAB) Topology Table for AS(27)/ID(1.1.1.1)

Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,

r – reply Status, s – sia Status

P 192.168.3.0/24, 2 successors, FD is 2048000, serno 26

via 10.0.12.2 (2048000/1392640), GigabitEthernet0/0/0

via 172.16.1.2 (2048000/1392640), GigabitEthernet0/0/1.1

P 172.16.13.0/24, 1 successors, FD is 1966080, serno 16

via 172.16.1.2 (1966080/1310720), GigabitEthernet0/0/1.1

via 10.0.12.2 (2621440/1966080), GigabitEthernet0/0/0

P 192.168.1.0/24, 1 successors, FD is 1310720, serno 3

via Connected, GigabitEthernet0/0/1.2

P 172.16.1.0/24, 1 successors, FD is 1310720, serno 2

via Connected, GigabitEthernet0/0/1.1

P 10.0.23.0/24, 1 successors, FD is 1966080, serno 27

via 10.0.12.2 (1966080/1310720), GigabitEthernet0/0/0

via 172.16.1.2 (2621440/1966080), GigabitEthernet0/0/1.1

P 10.0.12.0/24, 1 successors, FD is 1310720, serno 1

via Connected, GigabitEthernet0/0/0

We will focus on the routes, highlighted in the above output, to 192.168.3.0/24 and 10.0.23.0/24. There are several things to notice:

• The entry for the 192.168.3.0/24.0 network shows two successors, while the entry for 10.0.23.0/24 shows only one successor. Both entries show two paths. The path with the lowest Feasible Distance (FD) is selected as the successor and is offered to the routing table. For 192.168.3.0/24, there are two paths with equal FD (2048000). Therefore, both are successors and both are offered to the routing table. In the case of 10.0.23.0/24, the FD is listed as 19660800. The path via 10.0.12.2 shows that number as the FD (first number in parentheses). The path via 172.16.1.2 shows an FD of 2621440, which is higher than the current feasible distance. So that path, although valid, is a higher cost path and is not offered to the routing table.
• The FD listed in the topology table does not match the metric listed in the routing table. For 192.168.3.0/24, the routing table shows the metric value 16000, while the topology table shows the FD as 2048000. This is due to the routing table having a limit of 4 bytes (32 bits) for metric information while EIGRP on R1 is using EIGRP wide metrics, which are 64 bits. Wide metrics are used by Named EIGRP by default. To work around the 32-bit metric size limitation in the routing table, EIGRP divides the wide-metric value by the EIGRP_RIB_SCALE value, which defaults to 128, as you will see next in the output for the show ip protocols command. The value 2048000 divided by 128 is 16000.

Note: A network with mixed EIGRP implementations (Named and Classic in the same routing domain), will have some loss of route clarity which could lead to sub-optimal path selection. The recommended implementation is to use Named EIGRP in all cases.

• There are no feasible successors listed in the topology table for 192.168.3.0/24 or 10.0.23.0/24. The feasibility condition requires that the reported distance (RD) to a destination network be less than the current feasible distance for a next-hop to be considered a feasible successor to the route. In the case of 10.0.23.0/24, the RD of the path via 172.16.1.2 is the second number listed: (2621440/1966080). Because the RD is equal to the current FD, this route is disqualified as a feasible successor. If the path via 172.16.1.2 were to be lost, R1 would have to send queries to find a new way to get to 10.0.23.0/24. Feasible successors only exist in the topology table. Only successors appear in the routing table.
  5. To see the Routing Information Base (RIB) Scale and Metric Scale values, as well as other protocol information, issue the show ip protocols | section eigrp command.

R1# show ip protocols | section eigrp

Routing Protocol is “eigrp 27″

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 VR(BASIC-EIGRP-LAB) Address-Family Protocol for AS(27)

Metric weight K1=1, K2=0, K3=1, K4=0, K5=0 K6=0

Metric rib-scale 128

Metric version 64bit

Soft SIA disabled

NSF-aware route hold timer is 240

EIGRP NSF disabled

NSF signal timer is 20s

NSF converge timer is 120s

Router-ID: 1.1.1.1

Topology : 0 (base)

Active Timer: 3 min

Distance: internal 90 external 170

Maximum path: 4

Maximum hopcount 100

Maximum metric variance 1

Total Prefix Count: 5

Total Redist Count: 0

6. To examine details about a particular path, issue the show ip eigrp topology [address] command.

R1# show ip eigrp topology 192.168.3.0/24

EIGRP-IPv4 VR(BASIC-EIGRP-LAB) Topology Entry for AS(27)/ID(1.1.1.1) for 192.168.3.0/24

State is Passive, Query origin flag is 1, 2 Successor(s), FD is 2048000, RIB is 16000

Descriptor Blocks:

10.0.12.2 (GigabitEthernet0/0/0), from 10.0.12.2, Send flag is 0x0

Composite metric is (2048000/1392640), route is Internal

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 21250000 picoseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

Originating router is 3.3.3.3

172.16.1.2 (GigabitEthernet0/0/1.1), from 172.16.1.2, Send flag is 0x0

Composite metric is (2048000/1392640), route is Internal

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 21250000 picoseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

Originating router is 3.3.3.3

Close configuration window

Part 3:Tune EIGRP for IPv4

In this part of the lab, you will tune and optimize EIGRP for IPv4 through the use of passive interfaces, authentication, and variance.

Step 1:Configure specific interfaces as passive.

Passive interfaces are interfaces that only partially participate in a routing protocols operation. The network address for the passive interface is advertised through other interfaces. However, the routing protocol does not actually speak on the passive interface. Use passive interfaces when you have a connected network that you want to advertise, but you do not want protocol neighbors to appear on that interface. For example, interfaces supporting users should always be configured as passive. There are two ways to configure interfaces as passive, either specifically by interface name or by default. Normally a device with many LAN interfaces will use the default option, and then use the no form of the command on those specific interfaces that should be sending and receiving EIGRP messages.

1. On PC1, run Wireshark and set the capture filter to eigrp. You should see a hello message roughly every five seconds. If your device were capable of running EIGRP, you might be able to form an adjacency and interact in the routing domain. This is unnecessary traffic on the LAN and a potential security risk. Stop the capture.
2. On R1, configure af-interface G0/0/1 to be passive.

Open configuration window

R1(config)# router eigrp BASIC-EIGRP-LAB

R1(config-router)# address-family ipv4 unicast autonomous-system 27

R1(config-router-af)# af-interface g0/0/1.2

R1(config-router-af–interface)# passive-interface

R1(config-router-af–interface)# end

Close configuration window

3. On PC1, restart the Wireshark capture with the capture filter still configured for eigrp. You should no longer see EIGRP Hello messages.

Step 2:Configure interfaces to default to passive.

The second option for configuring passive interfaces is to configure them all as passive and then issue the no passive-interface command for certain interfaces. This approach is suitable in a security-focused scenario, or when the device has many LAN interfaces. The commands vary depending on whether you are using Classic or Named EIGRP.

1. In Classic EIGRP configuration, enter the passive-interface default command followed by no passive-interface interface-number commands for all the interfaces that should be participating in EIGRP. The following provides an example of this on R2. You will temporarily lose EIGRP adjacencies until passive-interface is removed from required interfaces.

Open configuration window

R2(config)# router eigrp 27

R2(config-router)# passive-interface default

R2(config-router)# no passive-interface g0/0/0

R2(config-router)# no passive-interface g0/0/1

R2(config-router)# exit

R2(config)# end

Close configuration window

2. In Named EIGRP configuration, you apply the passive-interface command to the af-interface default configuration, and the no passive-interface command to the specific af-interface interface-number. The following provides an example of this on R3. You will temporarily lose EIGRP adjacencies until passive-interface is removed from required interfaces.

Open configuration window

R3(config)# router eigrp BASIC-EIGRP-LAB

R3(config-router)# address-family ipv4 unicast autonomous-system 27

R3(config-router-af)# af-interface default

R3(config-router-af–interface)# passive-interface

R3(config-router-af–interface)# exit

R3(config-router-af)# af-interface g0/0/0

R3(config-router-af–interface)# no passive-interface

R3(config-router-af–interface)# exit

R3(config-router-af)# af-interface g0/0/1

R3(config-router-af–interface)# no passive-interface

R3(config-router-af–interface)# end

3. The output of the show ip protocols | section Passive command will give you a list of passive interfaces configured for EIGRP, which for R3 will only be the Loopback 0 interface that is simulating a LAN.

R3# show ip protocols | section Passive

Passive Interface(s):

Loopback0

Close configuration window

Step 3:Configure EIGRP authentication.

EIGRP supports authentication on an interface basis. In other words, each interface can be configured to require authentication of the connected peer. This ensures that connected devices that try to form an adjacency are authorized to do so. Classic EIGRP supports key-chain based MD5-hashed keys, while Named EIGRP adds support for SHA256-hashed keys. The two are not compatible.

In this step, you will configure both types of authentication to exercise the range of options available.

1. On R1, R2, R3, and D2, create a key-chain named EIGRP-AUTHEN-KEY with a single key. The key should have the key-string $3cre7!!

Open configuration window

R1(config)# key chain EIGRP-AUTHEN-KEY

R1(config-keychain)# key 1

R1(config-keychain-key)# key-string $3cre7!!

R1(config-keychain-key)# end

Close configuration window

2. On R2, configure interfaces G0/0/0 and G0/0/1 to encrypt the key chain you just created with MD5. Note that you will lose EIGRP adjacencies until the neighbor interfaces are configured.

Open configuration window

R2(config)# interface g0/0/0

R2(config-if)# ip authentication key-chain eigrp 27 EIGRP-AUTHEN-KEY

R2(config-if)# ip authentication mode eigrp 27 md5

R2(config-if)# exit

R2(config)# interface g0/0/1

R2(config-if)# ip authentication key-chain eigrp 27 EIGRP-AUTHEN-KEY

R2(config-if)# ip authentication mode eigrp 27 md5

R2(config-if)# end

Close configuration window

3. Configure interface G0/0/0 on both R1 and R3 to use the key chain with MD5. EIGRP adjacencies with R2 should be restored.

Open configuration window

R1(config)# router eigrp BASIC-EIGRP-LAB

R1(config-router)# address-family ipv4 unicast autonomous-system 27

R1(config-router-af)# af-interface g0/0/0

R1(config-router-af–interface)# authentication key-chain EIGRP-AUTHEN-KEY

R1(config-router-af–interface)# authentication mode md5

R1(config-router-af–interface)# end

4. Use the show ip eigrp interface detail | section Gi0/0/0 command to verify that authentication is in place and what type of authentication it is.

R1# show ip eigrp interface detail | section Gi0/0/0

Gi0/0/010/00/010/0500

Hello-interval is 5, Hold-time is 15

Split-horizon is enabled

Next xmit serial <none>

Packetized sent/expedited: 14/2

Hello’s sent/expedited: 186/4

Un/reliable mcasts: 0/11Un/reliable ucasts: 15/7

Mcast exceptions: 0CR packets: 0ACKs suppressed: 0

Retransmissions sent: 3Out-of-sequence rcvd: 0

Topology-ids on interface – 0

Authentication mode is md5,key-chain is “EIGRP-AUTHEN-KEY”

Topologies advertised on this interface:base

Topologies not advertised on this interface:

5. On R1 and D2, configure SHA 256 based authentication using the same $3cre7!! shared secret.. R1 and D2 are running Named EIGRP, so the configuration is applied in af-interface mode. On R1, configure the G0/0/1.1 subinterface. On D2, configure the G1/0/1 interface. The configuration for R1 is shown. Note that the R1-D2 adjacency will be lost until both ends are configured.

R1(config)# router eigrp BASIC-EIGRP-LAB

R1(config-router)# address-family ipv4 unicast autonomous-system 27

R1(config-router-af)# af-interface g0/0/1.1

R1(config-router-af–interface)# authentication mode hmac-sha-256 $3cre7!!

R1(config-router-af–interface)# end

Close configuration window

Open configuration window

D2(config)# router eigrp BASIC-EIGRP-LAB

D2(config-router)# address-family ipv4 unicast autonomous-system 27

D2(config-router-af)# af-interface g1/0/1

D2(config-router-af–interface)# authentication mode hmac-sha-256 $3cre7!!

D2(config-router-af–interface)# end

Close configuration window

6. Use the show ip eigrp interface detail command to verify that authentication is in place and what type of authentication it is.

Open configuration window

R1# show ip eigrp interface detail | section Gi0/0/1.1

Gi0/0/1.110/00/030/0500

Hello-interval is 5, Hold-time is 15

Split-horizon is enabled

Next xmit serial <none>

Packetized sent/expedited: 11/0

Hello’s sent/expedited: 225/4

Un/reliable mcasts: 0/11Un/reliable ucasts: 12/7

Mcast exceptions: 0CR packets: 0ACKs suppressed: 0

Retransmissions sent: 4Out-of-sequence rcvd: 0

Topology-ids on interface – 0

Authentication mode is HMAC-SHA-256, key-chain is not set

Topologies advertised on this interface:base

Topologies not advertised on this interface:

Close configuration window

Step 4:Manipulate load balancing with variance

By default, load balancing occurs only over equal-cost paths. EIGRP supports up to four equal cost paths by default but can be configured to support as many as 32 with the maximum-paths command.

EIGRP has the added capability to load balance over unequal-cost paths. Load balancing is controlled by the variance parameter. Its value is a multiplier that is used to determine how to deal with multiple paths to the same destination.

Variance is set to 1 by default, so any paths up to the configured maximum number of paths that have a feasible distance equal to the best current feasible distance are also offered to the routing table. This provides equal cost load balancing.

The variance parameter can also be set to zero, which dictates that no load balancing takes place.

The variance parameter can be adjusted so that paths that have an FD that is less than or equal to variance times current best FD are also considered as successors and installed into the routing table. There is an extremely important differentiation here — to be a feasible successor, the RD of a path must be less than the current best FD. To be considered for unequal load balancing, the FD of the feasible successor is multiplied by the variance value, and if the product of this calculation is less than the current best FD, the feasible successor is promoted to successor.

There are two caveats; first, only feasible successors are considered and second, unequal cost load balancing is unequal; traffic share is proportional to the best metric in the routing table for the given path.

Note: Keep in mind that your routing table may be different than the one created by the examples in this lab. If your results are different, examine them carefully to determine why so that you can thoroughly understand how EIGRP is operating.

1. On R3, there are two equal-cost paths to 192.168.1.0/24.

Open configuration window

R3# show ip route eigrp | section 192.168.1.0

D192.168.1.0/24

[90/20480] via 172.16.13.2, 00:08:18, GigabitEthernet0/0/1

[90/20480] via 10.0.23.2, 00:08:18, GigabitEthernet0/0/0

Close configuration window

2. To change this and allow for the demonstration of variance, change the interface bandwidth for the R2 interfaces G0/0/0 and G0/0/1 to 800000.

Open configuration window

R2(config)# interface g0/0/0

R2(config-if)# bandwidth 800000

R2(config-if)# exit

R2(config)# interface g0/0/1

R2(config-if)# bandwidth 800000

R2(config-if)# end

Close configuration window

3. When you examine the routing table on R3, you see that there is no load balancing occurring. All destinations have a single path.

Open configuration window

R3# show ip route eigrp | begin Gateway

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks

D10.0.12.0/24 [90/16640] via 10.0.23.2, 00:01:17, GigabitEthernet0/0/0

172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks

D172.16.1.0/24

[90/15360] via 172.16.13.2, 00:01:04, GigabitEthernet0/0/1

D192.168.1.0/24

[90/20480] via 172.16.13.2, 00:01:04, GigabitEthernet0/0/1

4. However, we know there are multiple paths in the network. The first consideration for manipulating variance is that it only works with feasible successors. Examining the topology table on R3 shows that there is a feasible successor for the 192.168.1.0/24 network. The route via 10.0.23.2 out the G0/0/0 interface has a RD less than the FD for the current successor.

R3# show ip eigrp topology | section 192.168.1.0

P 192.168.1.0/24, 1 successors, FD is 2621440

via 172.16.13.2 (2621440/1966080), GigabitEthernet0/0/1

via 10.0.23.2 (2785280/2129920), GigabitEthernet0/0/0

5. To use the other route for unequal cost load balancing, we can set the variance parameter to 2. This will mean that any path with an RD less than or equal to 5242880 will qualify as a successor (2 x 2621440 = 5242880).

R3(config)# router eigrp BASIC-EIGRP-LAB

R3(config-router)# address-family ipv4 unicast autonomous-system 27

R3(config-router-af)# topology base

R3(config-router-af–topology)# variance 2

R3(config-router-af–topology)# end

6. The output of the show ip route eigrp | begin Gateway command now displays two paths available to the 192.168.1.0/24 network. Notice that the routes have different metrics, but are listed and used just the same. Also, notice adding variance 2 adds a second path to the 10.0.12.0/24 network.

R3# show ip route eigrp | begin Gateway

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks

D10.0.12.0/24

[90/20480] via 172.16.13.2, 00:00:11, GigabitEthernet0/0/1

[90/16640] via 10.0.23.2, 00:00:11, GigabitEthernet0/0/0

172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks

D172.16.1.0/24

[90/15360] via 172.16.13.2, 00:00:11, GigabitEthernet0/0/1

D192.168.1.0/24

[90/20480] via 172.16.13.2, 00:00:11, GigabitEthernet0/0/1

[90/21760] via 10.0.23.2, 00:00:11, GigabitEthernet0/0/0

7. Issue the show ip route 192.168.1.0 command to see more details about the paths the router has to the 192.168.1.0 network. As a part of this output, you see the traffic share count, which tells you the ratio of traffic that will be sent between these links. In this example, the count is 120 via 172.16.13.2 and 113 via 10.0.23.2. What that means is that 120 packets will be sent via 172.16.13.2 and then 113 packets will be sent via 10.0.23.2.

R3# show ip route 192.168.1.0

Routing entry for 192.168.1.0/24

Known via “eigrp 27″, distance 90, metric 20480, type internal

Redistributing via eigrp 27

Last update from 10.0.23.2 on GigabitEthernet0/0/0, 00:01:42 ago

Routing Descriptor Blocks:

* 172.16.13.2, from 172.16.13.2, 00:01:42 ago, via GigabitEthernet0/0/1

Route metric is 20480, traffic share count is 120

Total delay is 30 microseconds, minimum bandwidth is 1000000 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 2

10.0.23.2, from 10.0.23.2, 00:01:42 ago, via GigabitEthernet0/0/0

Route metric is 21760, traffic share count is 113

Total delay is 30 microseconds, minimum bandwidth is 800000 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 2

Close configuration window

End of document

Router Interface Summary Table

Note: To find out how the router is configured, look at the interfaces to identify the type of router and how many interfaces the router has. There is no way to effectively list all the combinations of configurations for each router class. This table includes identifiers for the possible combinations of Ethernet and Serial interfaces in the device. The table does not include any other type of interface, even though a specific router may contain one. An example of this might be an ISDN BRI interface. The string in parenthesis is the legal abbreviation that can be used in Cisco IOS commands to represent the interface.

End of document

Device Configs – Final

Router R1

R1# show run

Building configuration…

Current configuration : 2152 bytes

!

version 16.9

service timestamps debug datetime msec

service timestamps log datetime msec

platform qfp utilization monitor load 80

no platform punt-keepalive disable-kernel-core

!

hostname R1

!

boot-start-marker

boot-end-marker

!

no aaa new-model

!

no ip domain lookup

!

ip dhcp pool HOSTS

network 192.168.1.0 255.255.255.0

default-router 192.168.1.1

!

login on-success log

!

subscriber templating

!

multilink bundle-name authenticated

!

!

key chain EIGRP-AUTHEN-KEY

key 1

key-string $3cre7!!

!

spanning-tree extend system-id

!

redundancy

mode none

!

interface GigabitEthernet0/0/0

ip address 10.0.12.1 255.255.255.0

negotiation auto

!

interface GigabitEthernet0/0/1

no ip address

negotiation auto

!

interface GigabitEthernet0/0/1.1

encapsulation dot1Q 1 native

ip address 172.16.1.1 255.255.255.0

!

interface GigabitEthernet0/0/1.2

encapsulation dot1Q 2

ip address 192.168.1.1 255.255.255.0

!

interface Serial0/1/0

no ip address

!

interface Serial0/1/1

no ip address

!

router eigrp BASIC-EIGRP-LAB

!

address-family ipv4 unicast autonomous-system 27

!

af-interface GigabitEthernet0/0/1.2

passive-interface

exit-af-interface

!

af-interface GigabitEthernet0/0/0

authentication mode md5

authentication key-chain EIGRP-AUTHEN-KEY

exit-af-interface

!

af-interface GigabitEthernet0/0/1.1

authentication mode hmac-sha-256 $3cre7!!

exit-af-interface

!

topology base

exit-af-topology

network 10.0.12.0 0.0.0.255

network 172.16.1.0 0.0.0.255

network 192.168.1.0

eigrp router-id 1.1.1.1

exit-address-family

!

ip forward-protocol nd

no ip http server

ip http secure-server

!

control-plane

!

banner motd ^C R1, Implement EIGRP for IPv4 ^C

!

line con 0

exec-timeout 0 0

logging synchronous

transport input none

stopbits 1

line aux 0

stopbits 1

line vty 0 4

exec-timeout 0 0

privilege level 15

password cisco123

login

!

end

Router R2

R2# show run

Building configuration…

Current configuration : 1642 bytes

!

version 16.9

service timestamps debug datetime msec

service timestamps log datetime msec

platform qfp utilization monitor load 80

no platform punt-keepalive disable-kernel-core

!

hostname R2

!

boot-start-marker

boot-end-marker

!

no aaa new-model

!

no ip domain lookup

!

login on-success log

!

subscriber templating

!

multilink bundle-name authenticated

!

key chain EIGRP-AUTHEN-KEY

key 1

key-string $3cre7!!

!

spanning-tree extend system-id

!

redundancy

mode none

!

interface GigabitEthernet0/0/0

bandwidth 800000

ip address 10.0.12.2 255.255.255.0

ip authentication mode eigrp 27 md5

ip authentication key-chain eigrp 27 EIGRP-AUTHEN-KEY

negotiation auto

!

interface GigabitEthernet0/0/1

bandwidth 800000

ip address 10.0.23.2 255.255.255.0

ip authentication mode eigrp 27 md5

ip authentication key-chain eigrp 27 EIGRP-AUTHEN-KEY

negotiation auto

!

router eigrp 27

network 10.0.0.0 0.0.31.255

passive-interface default

no passive-interface GigabitEthernet0/0/0

no passive-interface GigabitEthernet0/0/1

eigrp router-id 2.2.2.2

!

ip forward-protocol nd

no ip http server

ip http secure-server

!

control-plane

!

banner motd ^C R2, Implement EIGRP for IPv4 ^C

!

line con 0

exec-timeout 0 0

logging synchronous

transport input none

stopbits 1

line aux 0

stopbits 1

line vty 0 4

exec-timeout 0 0

privilege level 15

password cisco123

login

!

end

Router R3

R3# show run

Building configuration…

Current configuration : 1984 bytes

!

version 16.9

service timestamps debug datetime msec

service timestamps log datetime msec

platform qfp utilization monitor load 80

no platform punt-keepalive disable-kernel-core

!

hostname R3

!

boot-start-marker

boot-end-marker

!

no aaa new-model

!

no ip domain lookup

!

login on-success log

!

subscriber templating

!

multilink bundle-name authenticated

!

key chain EIGRP-AUTHEN-KEY

key 1

key-string $3cre7!!

!

diagnostic bootup level minimal

!

spanning-tree extend system-id

!

redundancy

mode none

!

interface Loopback0

ip address 192.168.3.1 255.255.255.0

!

interface GigabitEthernet0/0/0

ip address 10.0.23.3 255.255.255.0

negotiation auto

!

interface GigabitEthernet0/0/1

ip address 172.16.13.1 255.255.255.0

negotiation auto

!

interface Serial0/1/0

no ip address

!

interface Serial0/1/1

no ip address

!

router eigrp BASIC-EIGRP-LAB

!

address-family ipv4 unicast autonomous-system 27

!

af-interface default

passive-interface

exit-af-interface

!

af-interface GigabitEthernet0/0/0

authentication mode md5

authentication key-chain EIGRP-AUTHEN-KEY

no passive-interface

exit-af-interface

!

af-interface GigabitEthernet0/0/1

no passive-interface

exit-af-interface

!

topology base

variance 2

exit-af-topology

network 10.0.23.0 0.0.0.255

network 172.16.13.0 0.0.0.255

network 192.168.3.0

eigrp router-id 3.3.3.3

exit-address-family

!

ip forward-protocol nd

no ip http server

ip http secure-server

!

control-plane

!

banner motd ^C R3, Implement EIGRP for IPv4 ^C

!

line con 0

exec-timeout 0 0

logging synchronous

transport input none

stopbits 1

line aux 0

stopbits 1

line vty 0 4

exec-timeout 0 0

privilege level 15

password cisco123

login

!

end

Switch D1

D1# show run

Building configuration…

Current configuration : 6666 bytes

!

version 16.9

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

! Call-home is enabled by Smart-Licensing.

service call-home

no platform punt-keepalive disable-kernel-core

!

hostname D1

!

vrf definition Mgmt-vrf

!

address-family ipv4

exit-address-family

!

address-family ipv6

exit-address-family

!

no aaa new-model

switch 1 provision ws-c3650-24td

!

no ip domain lookup

!

login on-success log

!

license boot level ipservicesk9

!

diagnostic bootup level minimal

!

spanning-tree mode rapid-pvst

spanning-tree extend system-id

!

redundancy

mode sso

!

transceiver type all

monitoring

!

class-map match-any system-cpp-police-topology-control

description Topology control

class-map match-any system-cpp-police-sw-forward

description Sw forwarding, L2 LVX data, LOGGING

class-map match-any system-cpp-default

description Inter FED, EWLC control, EWLC data

class-map match-any system-cpp-police-sys-data

description Learning cache ovfl, High Rate App, Exception, EGR Exception, NFLSAMPLED DATA, RPF Failed

class-map match-any system-cpp-police-punt-webauth

description Punt Webauth

class-map match-any system-cpp-police-l2lvx-control

description L2 LVX control packets

class-map match-any system–cpp-police-forus

description Forus Address resolution and Forus traffic

class-map match-any system-cpp-police-multicast-end-station

description MCAST END STATION

class-map match-any system-cpp-police-multicast

description Transit Traffic and MCAST Data

class-map match-any system-cpp-police-l2-control

description L2 control

class-map match-any system-cpp-police-dot1x-auth

description DOT1X Auth

class-map match-any system-cpp-police-data

description ICMP redirect, ICMP_GEN and BROADCAST

class-map match-any system-cpp-police-stackwise–virt-control

description Stackwise Virtual

class-map match-any non-client-nrt-class

class-map match-any system-cpp-police-routing-control

description Routing control and Low Latency

class-map match-any system-cpp–police-protocol-snooping

description Protocol snooping

class-map match-any system-cpp-police-dhcp-snooping

description DHCP snooping

class-map match-any system-cpp-police-system-critical

description System Critical and Gold Pkt

!

policy-map system-cpp-policy

!

interface GigabitEthernet0/0

vrf forwarding Mgmt-vrf

no ip address

negotiation auto

!

interface GigabitEthernet1/0/1

switchport mode access

spanning-tree portfast

!

interface GigabitEthernet1/0/2

shutdown

!

interface GigabitEthernet1/0/3

shutdown

!

interface GigabitEthernet1/0/4

shutdown

!

interface GigabitEthernet1/0/5

shutdown

!

interface GigabitEthernet1/0/6

shutdown

!

interface GigabitEthernet1/0/7

shutdown

!

interface GigabitEthernet1/0/8

shutdown

!

interface GigabitEthernet1/0/9

shutdown

!

interface GigabitEthernet1/0/10

shutdown

!

interface GigabitEthernet1/0/11

switchport mode trunk

!

interface GigabitEthernet1/0/12

shutdown

!

interface GigabitEthernet1/0/13

shutdown

!

interface GigabitEthernet1/0/14

shutdown

!

interface GigabitEthernet1/0/15

shutdown

!

interface GigabitEthernet1/0/16

shutdown

!

interface GigabitEthernet1/0/17

shutdown

!

interface GigabitEthernet1/0/18

shutdown

!

interface GigabitEthernet1/0/19

shutdown

!

interface GigabitEthernet1/0/20

shutdown

!

interface GigabitEthernet1/0/21

shutdown

!

interface GigabitEthernet1/0/22

shutdown

!

interface GigabitEthernet1/0/23

switchport access vlan 2

switchport mode access

spanning-tree portfast

!

interface GigabitEthernet1/0/24

shutdown

!

interface GigabitEthernet1/1/1

shutdown

!

interface GigabitEthernet1/1/2

shutdown

!

interface TenGigabitEthernet1/1/3

!

interface TenGigabitEthernet1/1/4

!

interface Vlan1

no ip address

!

ip forward-protocol nd

ip http server

ip http secure-server

!

control-plane

service-policy input system-cpp-policy

!

banner motd ^C D1, Implement EIGRP for IPv4 ^C

!

line con 0

exec-timeout 0 0

logging synchronous

stopbits 1

line aux 0

stopbits 1

line vty 0 4

exec-timeout 0 0

privilege level 15

password cisco123

login

line vty 5 15

login

!

end

Switch D2

D2# show run

Building configuration…

Current configuration : 7011 bytes

!

version 16.9

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

! Call-home is enabled by Smart-Licensing.

service call-home

no platform punt-keepalive disable-kernel-core

!

hostname D2

!

vrf definition Mgmt-vrf

!

address-family ipv4

exit-address-family

!

address-family ipv6

exit-address-family

!

no aaa new-model

switch 1 provision ws-c3650-24td

!

ip routing

!

no ip domain lookup

!

login on-success log

!

key chain EIGRP-AUTHEN-KEY

key 1

key-string $3cre7!!

!

license boot level ipservicesk9

!

diagnostic bootup level minimal

!

spanning-tree mode rapid-pvst

spanning-tree extend system-id

!

redundancy

mode sso

!

transceiver type all

monitoring

!

class-map match-any system-cpp-police-topology-control

description Topology control

class-map match-any system-cpp-police-sw-forward

description Sw forwarding, L2 LVX data, LOGGING

class-map match-any system-cpp-default

description Inter FED, EWLC control, EWLC data

class-map match-any system-cpp-police-sys-data

description Learning cache ovfl, High Rate App, Exception, EGR Exception, NFLSAMPLED DATA, RPF Failed

class-map match-any system-cpp-police-punt-webauth

description Punt Webauth

class-map match-any system-cpp-police-l2lvx-control

description L2 LVX control packets

class-map match-any system-cpp-police-forus

description Forus Address resolution and Forus traffic

class-map match-any system-cpp-police-multicast-end-station

description MCAST END STATION

class-map match-any system-cpp-police-multicast

description Transit Traffic and MCAST Data

class-map match-any system-cpp-police-l2-control

description L2 control

class-map match-any system-cpp-police-dot1x-auth

description DOT1X Auth

class-map match-any system-cpp-police-data

description ICMP redirect, ICMP_GEN and BROADCAST

class-map match-any system-cpp-police-stackwise–virt-control

description Stackwise Virtual

class-map match-any non-client-nrt-class

class-map match-any system-cpp-police-routing-control

description Routing control and Low Latency

class-map match-any system-cpp-police-protocol-snooping

description Protocol snooping

class-map match-any system-cpp-police-dhcp-snooping

description DHCP snooping

class-map match-any system-cpp-police-system-critical

description System Critical and Gold Pkt

!

policy-map system-cpp-policy

!

interface GigabitEthernet0/0

vrf forwarding Mgmt-vrf

no ip address

negotiation auto

!

interface GigabitEthernet1/0/1

no switchport

ip address 172.16.1.2 255.255.255.0

!

interface GigabitEthernet1/0/2

shutdown

!

interface GigabitEthernet1/0/3

shutdown

!

interface GigabitEthernet1/0/4

shutdown

!

interface GigabitEthernet1/0/5

shutdown

!

interface GigabitEthernet1/0/6

shutdown

!

interface GigabitEthernet1/0/7

shutdown

!

interface GigabitEthernet1/0/8

shutdown

!

interface GigabitEthernet1/0/9

shutdown

!

interface GigabitEthernet1/0/10

shutdown

!

interface GigabitEthernet1/0/11

no switchport

ip address 172.16.13.2 255.255.255.0

!

interface GigabitEthernet1/0/12

shutdown

!

interface GigabitEthernet1/0/13

shutdown

!

interface GigabitEthernet1/0/14

shutdown

!

interface GigabitEthernet1/0/15

shutdown

!

interface GigabitEthernet1/0/16

shutdown

!

interface GigabitEthernet1/0/17

shutdown

!

interface GigabitEthernet1/0/18

shutdown

!

interface GigabitEthernet1/0/19

shutdown

!

interface GigabitEthernet1/0/20

shutdown

!

interface GigabitEthernet1/0/21

shutdown

!

interface GigabitEthernet1/0/22

shutdown

!

interface GigabitEthernet1/0/23

shutdown

!

interface GigabitEthernet1/0/24

shutdown

!

interface GigabitEthernet1/1/1

shutdown

!

interface GigabitEthernet1/1/2

shutdown

!

interface TenGigabitEthernet1/1/3

!

interface TenGigabitEthernet1/1/4

!

interface Vlan1

no ip address

!

router eigrp BASIC-EIGRP-LAB

!

address-family ipv4 unicast autonomous-system 27

!

af-interface GigabitEthernet1/0/1

authentication mode hmac-sha-256 $3cre7!!

exit-af-interface

!

topology base

exit-af-topology

network 172.16.0.0

eigrp router-id 132.132.132.132

exit-address-family

!

ip forward-protocol nd

ip http server

ip http secure-server

!

control-plane

service-policy input system-cpp-policy

!

banner motd ^C D2, Implement EIGRP for IPv4 ^C

!

line con 0

exec-timeout 0 0

logging synchronous

stopbits 1

line aux 0

stopbits 1

line vty 0 4

exec-timeout 0 0

privilege level 15

password cisco123

login

line vty 5 15

login

!

end

• Recommend