Hello Samir
First of all, that behavior is a little bit unusual. If you have a topology where the DR/BDR are already established, and you add another router that does not have a higher priority (such as R3 in your case), an election is not triggered. R3 will send out a neighbor discovery with a value of 0.0.0.0 for the DR/BDR, but will receive a response letting it know that the DR/BDR is already established, and it has a better priority. This exchange is not considered an election. I assume that’s what’s happening in your case, but it’s just a matter of terminology.
But even if R3 had a higher priority, it should still not trigger an election. This is because in OSPF, DR/BDR elections are preemptive. This means that even if a new router with a higher priority or RID comes into the network after the DR and BDR have been elected, it will not take over the role of DR or BDR until one of them goes down. This is done to maintain stability in the network.
Can you give us some more information about this? When you say “two additional elections” are they minutes apart, seconds apart, when do they take place exactly? And is there any event that occurs at around that time? Also, you mention that these two additional elections take place on both R2 and R1, but not R3?? So the current DR and BDR reaffirm their statuses as DR and BDR and R3 does not participate in this? Are you sure they’re elections and not just an exchange of hello packets?
Indeed, the only events that should trigger a new election is if the current DR or BDR fails (their interface goes down) or if there is network instability, or if the OSPF process restarts. Beyond that, if it occurs, it may be due to hardware or software problems.
Let us know more info, and if you can share an example of the debugs you see, maybe we can help you out further.
I hope this has been helpful!
Laz