Root: WRM Database > Information Technology > Certifications > CCNA > Routing Protocols > OSPF > DR Elections > The OSPF DR Election Process
Root: WRM Database > Information Technology > Certifications > CCNA > Routing Protocols > OSPF > Priority Values > The OSPF DR Election Process
Root: WRM Database > Information Technology > Certifications > CCNA > Routing Protocols > OSPF > BDRs > The OSPF DR Election Process
Root: WRM Database > Information Technology > Certifications > CCNA > Routing Protocols > OSPF > RIDs > The OSPF DR Election Process



The OSPF DR Election Process


When a DR is required, the neighboring routers hold an election. To elect a DR, the neighboring routers look at two fields inside the Hello packets they receive and choose the DR based on the following criteria:

• The router sending the Hello with the highest OSPF priority setting becomes the DR.
• If two or more routers tie with the highest OSPF priority setting, the router sending the Hello with the highest RID wins.
• It's not always the case, but typically the router with the second-highest OSPF priority becomes the BDR.
• An OSPF priority setting of 0 means that the router does not participate in the election and can never become the DR or BDR.
• The range of OSPF priority values that allow a router to be a candidate are 1 through 255.
• If a new, better candidate comes along after the DR and BDR have been elected, the new candidate does not preempt the existing DR and BDR.







References

Odom, Wendell (2008) CCNA ICND2 Official Exam Certification Guide, Second Edition. Indianapolis: Cisco Press.