JNCIS-ENT JN0-351 Juniper Study Notes

 In OSPF, a DR (Designated Router) and a BDR (Backup Designated Router) are elected on each multi-access network, such as Ethernet or Frame Relay. The DR and BDR are responsible for exchanging routing information with other routers on the same network segment. The election is based on two criteria: the OSPF priority and the router ID. The router with the highest priority becomes the DR, and the router with the second-highest priority becomes the BDR. If the priorities are equal, the router with the highest router ID becomes the DR, and the router with the second-highest router ID becomes the BDR. The default priority is 1, and the router ID is either manually configured or derived from the highest IP address on any interface12.

In this scenario, R1 has a priority of 32 and a router ID of 192.168.1.2, and R2 has a priority of 64 and a router ID of 192.168.1.1. Since R2 has a higher priority than R1, it will become the BDR. The router ID does not matter in this case, because the priority is different. Therefore, the correct answer is C.

The other options are not correct because:

A. At least two routers are required for a DR/BDR election, not three2.

B. Router IDs do not have to match for an adjacency to form, they just have to be unique3.

D. R1 will not be the BDR, because it has a lower priority than R212.

The feature that enables an interface on an EX Series switch to receive both untagged traffic (from the computer) and tagged traffic (from the IP phone) is the  voice VLAN 1 2 .

The voice VLAN feature in EX-series switches enables access ports to accept both data (untagged) and voice (tagged) traffic and separate that traffic into different VLANs 1 2 .  This allows the switch to differentiate between voice and data traffic, ensuring that voice traffic can be treated with a higher priority 1 2 . Therefore, option D is correct.