OSPF: Neighbor state after DR/BDR election

[ManiAm]

trafficstars

According to the OSPF RFC, each interface connected to a broadcast or NBMA network is assigned a Wait timer with default value of 40s. Once the timer is expired, the DR/BDR election is started for that interface. Once the election is over, a DROTHER router establishes full-adjacency with both DR and BDR and 2-way adjacency with other DROTHERs.

I have created a simple scenario in Cisco packet tracer consisting of six OSPF routers connected to an Ethernet switch. As you can see, the adjacency status are as expected. All routers have priority 1 and the router with highest router id would be DR and the next highest would be BDR.

I created the same scenario in INET (BTW, I love the INET visualizer).

Now look at the neighbors + neighbor status in router R3 (you might need to click on the pic to zoom-in). Also note that neighbor status is not shown in the current OSPF implementation and you need to check commit 7bf3f39 from my pull request.

In the OSPF implementation, the DR and BDR are elected correctly, but R3 (which is a DROTHER) forms 2-way status even with DR/BDR (it should be full). When we continue the simulation, the 2-way state transitions to full which is not expected again! It means that all routers form full-mesh adjacency with each other! The whole purpose of the DR/BDR election is to prevent full-mesh adjacency.

[levy]

Do you think that this issue is fixed with the merge of your OSPF improvements into maser?

[ManiAm]

Unfortunate no!

However, this issue is related to the performance of OSPF and will not affect the main function of OSPF. I will take a look at this, once high priority tasks that I want to focus on are done :)