During a recent OSPF election among three routers, RTA was elected the DR and RTB was
elected the BDR, as seen in the graphic. Assume that RTA fails, and that RTB takes the
place of the DR while RTC becomes the new BDR. What will happen when RTA comes back
online?
A.
A new election will take place establishing an all new DR and BDR based on configured
priority levels and MAC addresses.
B.
RTA will take the place of DR immediately upon establishing its adjacencies.
C.
RTA will take the place of DR only if RTB fails.
D.
RTA will take the place of DR only if both RTB and RTC fail.
Explanation:
If a router with a higher priority value gets added to the network, it does not preempt the DR
and BDR. The only time a DR and BDR changes is if one of them is out of service. If the DR
is out of service, the BDR becomes the DR, and a new BDR is selected. If the BDR is out of
service, a new BDR is elected. In a multi-access network, the router that is powered on first
will generally become the DR, since the DR/BDR process is not pre-emptive.
: CCNP Self-Study Second Edition P.243