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2.3.11 Packet Tracer - Determine the DR and BDR - ILM

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Course

Routing & Switching (CNET 311)

33 Documents
Students shared 33 documents in this course
Academic year: 2022/2023
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Narjot Kaur
Centennial College
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Packet Tracer - Determine the DR and BDR Addressing Table

Device Interface IP Address Subnet Mask

RA G0/0 192.168.1 255.255.

RA Lo0 192.168.31 255.255.

RB G0/0 192.168.1 255.255.

RB Lo0 192.168.31 255.255.

RC G0/0 192.168.1 255.255.

RC Lo0 192.168.31 255.255.

Objectives

Part 1: Examine DR and BDR Changing Roles

Part 2: Modify OSPF Priority and Force Elections

Scenario

In this activity, you will examine DR and BDR roles and watch the roles change when there is a change in the

network. You will then modify the priority to control the roles and force a new election. Finally, you will verify

routers are filling the desired roles.

Instructions

Part 1: Examine DR and BDR Changing Roles

Step 1: Wait until the amber link lights turn green.

When you first open the file in Packet Tracer, you may notice that the link lights for the switch are amber.

These link lights will stay amber for 50 seconds while the STP protocol on the switch makes sure that one of

the routers is not another switch. Alternatively, you can click Fast Forward Time to bypass this process.

Step 2: Verify the current OSPF neighbor states.

Use the appropriate command on each router to examine the current DR and BDR. If a router shows

Open configuration windowFULL/DROTHER it means that the router is not a DR or a BDR.

RA# show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

192.168.31 2 FULL/DR 00:00:35 192.168.1 GigabitEthernet0/

192.168.31 1 FULL/BDR 00:00:35 192.168.1 GigabitEthernet0/

RB# show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

192.168.31 1 FULL/DROTHER 00:00:36 192.168.1 GigabitEthernet0/

192.168.31 2 FULL/DR 00:00:36 192.168.1 GigabitEthernet0/

Packet Tracer - Determine the DR and BDR

RC# show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface
192.168.31 1 FULL/DROTHER 00:00:39 192.168.1 GigabitEthernet0/
192.168.31 1 FULL/BDR 00:00:38 192.168.1 GigabitEthernet0/
Questions:

Which router is the DR?

Type your answers here.

RC

Which router is the BDR?

Type your answers here.

RB

What is the OSPF state of router RA?

Type your answers here.

DROTHER

Step 3: Turn on IP OSPF adjacency debugging.

You can monitor the DR and BDR election process with a debug command. On RA and RB, enter the

following command.

RA# debug ip ospf adj

RB# debug ip ospf adj

Step 4: Disable the Gigabit Ethernet 0/0 interface on RC.

a. Use the shutdown command to disable the link between RC and the switch to cause roles to change.

b. Wait about 30 seconds for the dead timers to expire on RA and RB.

Question:

According to the debug output, which router was elected DR and which router was elected BDR?

Type your answers here.

RB is now DR and RA is now BDR.

Step 5: Restore the Gigabit Ethernet 0/0 interface on RC.

a. Re-enable the link between RC and the switch.

b. Wait for the new DR/BDR elections to occur.

Question:

Did DR and BDR roles change? Explain.

Type your answers here.

No, because OSPF does not update the DR/BDR when the existing ones are active.

c. Verify the DR and BDR assignments using the show ip ospf neighbor command on router RC.

RC# show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface
192.168.31 1 FULL/DR 00:00:34 192.168.1 GigabitEthernet0/
192.168.31 1 FULL/BDR 00:00:34 192.168.1 GigabitEthernet0/

Packet Tracer - Determine the DR and BDR

RC(config-if)# ip ospf priority 1

Step 2: Force an election by resetting the OSPF process on the routers.

Starting with router RA, issue the clear ip ospf process on each router to reset the OSPF process.

Step 3: Verify DR and BDR elections were successful.

Wait long enough for OSPF to converge and for the DR/BDR election to occur. This should take a few

minutes. You can click Fast Forward Time to speed up the process.

Question:

According to output from the show ip ospf neighbor command on the routers, which router is now DR and

which router is now BDR?

Type your answers here.

RA is now DR and RB is now BDR.

Close configuration window

Note: If the routers do not elect the correct DR and BDR after setting the OSPF priorities try restarting Packet

Tracer.

End of document
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2.3.11 Packet Tracer - Determine the DR and BDR - ILM

Course: Routing & Switching (CNET 311)

33 Documents
Students shared 33 documents in this course

University: Centennial College

Was this document helpful?
Packet Tracer - Determine the DR and BDR Addressing Table
Device Interface IP Address Subnet Mask
RA G0/0 192.168.1.1 255.255.255.0
RA Lo0 192.168.31.11 255.255.255.255
RB G0/0 192.168.1.2 255.255.255.0
RB Lo0 192.168.31.22 255.255.255.255
RC G0/0 192.168.1.3 255.255.255.0
RC Lo0 192.168.31.33 255.255.255.255
Objectives
Part 1: Examine DR and BDR Changing Roles
Part 2: Modify OSPF Priority and Force Elections
Scenario
In this activity, you will examine DR and BDR roles and watch the roles change when there is a change in the
network. You will then modify the priority to control the roles and force a new election. Finally, you will verify
routers are filling the desired roles.
Instructions
Part 1: Examine DR and BDR Changing Roles
Step 1: Wait until the amber link lights turn green.
When you first open the file in Packet Tracer, you may notice that the link lights for the switch are amber.
These link lights will stay amber for 50 seconds while the STP protocol on the switch makes sure that one of
the routers is not another switch. Alternatively, you can click Fast Forward Time to bypass this process.
Step 2: Verify the current OSPF neighbor states.
Use the appropriate command on each router to examine the current DR and BDR. If a router shows
FULL/DROTHER it means that the router is not a DR or a BDR.
Open configuration window
RA# show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.31.33 2 FULL/DR 00:00:35 192.168.1.3 GigabitEthernet0/0
192.168.31.22 1 FULL/BDR 00:00:35 192.168.1.2 GigabitEthernet0/0
RB# show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.31.11 1 FULL/DROTHER 00:00:36 192.168.1.1 GigabitEthernet0/0
192.168.31.33 2 FULL/DR 00:00:36 192.168.1.3 GigabitEthernet0/0
2013 - 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 1 of 4www.netacad.com

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