Is it possible, to have a DR as a Slave Router?
So here is my knowledge:
The DR and the BDR are elected based on priority and then highest RID in an area, so every router can communicate with the DR instead of every router with every router, to minimize network traffic. Although it is possible, that a router with lower RID is elected, if it started faster.
The Master and the Slave router is elected only during LSA exchange. The master is elected from a higher RID and the Slave with the lower RID. After the exchange, the master and slave "descriptions" are dropped.
Example for when it could happen:
- Router 1 (ID: 1.1.1.1, Prio: 5)
- Router 2 (ID: 2.2.2.2, Prio: 1)
- Router 3 (ID: 3.3.3.3, Prio: 3)
From my knowledge, R1 will be selected as the DR, R3 as the BDR and R2 as normal router. During an exchange between R1 and R2, R1 will be the Slave and R2 will be the Master.
Here are some links from my research:
- https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13684-12.html
- https://community.cisco.com/t5/switching/ospf-master-slave-dr-bdr-election/td-p/2526774
All my collegues, including my boss says that the DR and the Master router is the exact same thing, so please correct me if I am wrong or give me some sources to prove them wrong.
Thanks :)