thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Routing & Switching · Intermediate

Designated Router (DR)

The OSPF router elected on a multi-access segment to form full adjacencies with all others and originate the Type 2 LSA.

Definition

The DR reduces adjacencies and flooding on broadcast and NBMA networks: all routers become Full with the DR and BDR and remain 2-Way with each other. Election uses the highest interface priority, then the highest router ID, and is non-preemptive. Routers send updates to the DR/BDR on 224.0.0.6, and the DR floods to 224.0.0.5.

Example

ip ospf priority 255 on the intended DR interface

Exam tip

DR election is non-preemptive; a higher-priority router added later does not take over until the process or interface resets.

Related terms