CCDE: Cisco Certified Design Expert (Written) — Question 11

A company is planning to connect its 30 sites with a VPLS WAN backbone. A router at each site should establish neighborships with all other routers using the
OSPF routing protocol. Which three points must be considered regarding DR and BDR when different router platforms are used? (Choose three.)

Answer options

• A. It is a best practice that the routers with the most powerful hardware should take the role of the DR and BDR.
• B. If the IP OSPF priority is the same for all routers, the highest loopback IP address and router ID will decide which routers will take the DR and BDR role during the selection process.
• C. To select the DR and BDR, the IP OSPF priority must be set to a higher value than the default value at the DR and BDR during the selection process.
• D. To select the DR and BDR, the IP OSPF priority must be set to a lower value than the default value at the DR and BDR during the selection process.
• E. The role for the DR and BDR will be selected when a new OSPF router comes up.
• F. To force two routers to become a DR and a BDR, the IP OSPF priority can be set to zero at all other OSPF routers.

Correct answer: A, B, F

Explanation

Option A is correct because it is generally advisable for the more powerful hardware to handle the DR and BDR roles for better performance. Option B is also correct, as the highest loopback IP address and router ID will determine the roles if priorities are equal. Option F is valid because setting the OSPF priority to zero for other routers ensures that the designated routers become DR and BDR. Options C and D are incorrect because the priority must be higher, not lower, to have a significant impact on the selection process.