Information Technology Reference
In-Depth Information
In addition to configuring loopbacks, it would be a good idea to configure RTA with an OSPF priority
that would ensure that it always wins the DR/BDR election. The syntax for configuring OSPF priority
is as follows:
Router(config-if)#
ip ospf priority
priority
Document the commands you would use to configure RTA to make sure that its priority will always
win the DR/BDR election.
RTA(config)#
interface Fa 0/0
RTA(config-if)#
ip ospf priority 2
!Any priority higher than the default of 1 will work.
DR/BDR Election Exercise
In the following exercises, assume that all routers are simultaneously booted. Determine the network
type, if applicable, and label which router is elected as the DR and which router is elected as the BDR.
Hint: Remember, if priority is equal, router ID determines the DR and BDR.
Refer to Figure 11-7 and answer the following questions.
Figure 11-7
DR/BDR Election Exercise 1 Topology (Answer)
Fa0/0 = 172.16.1.1
Lo0 = 192.168.1.4
Fa0/0 = 172.16.1.2
Lo0 = 192.168.1.3
RTA
RTB
RTC
RTD
Fa0/0 = 172.16.1.3
S0/0/0 = 192.168.5.1
Lo0 = 192.168.1.2
Fa0/0 = 172.16.1.4
S0/0/0 = 192.168.5.2
Lo0 = 192.168.1.1
The loopback address is
the router ID in every case.
What is the router ID for RTA?
192.168.1.4
What is the router ID for RTB?
192.168.1.3
What is the router ID for RTC?
192.168.1.2
What is the router ID for RTD?
192.168.1.1
Which router will be elected the DR?
RTA
Which router will be elected the BDR?
RTB
Refer to Figure 11-8 and, in the table that follows, determine whether there will be a DR/BDR
election. If applicable, designate which router is the DR and which router is the BDR.
