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2.3.11 Packet Tracer - Determine the DR and BDR
Course: Computer Networking (IM4761)
University: Nanyang Technological University
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Packet Tracer - Determine the DR and BDR
Addressing Table
Device Interface IP Address Subnet Mask
RA G0/0 192.168.1.1 255.255.255.0
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
a. 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.
b. 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
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