OSPF DR/BDR election

[wiztech]

Consider using OSPF in broadcast access media where we have DR/BDR election process. When we add a new router running OSPF to the network does the election process takes place again? Can we change that (i.e. manually stopping the election process from taking place or manually force the election process to start)?

[nstringf]

No a new DR/BDR election will not take place if there are already 2 routers defined as the DR/BDR respectively. When the 3rd router comes on line, it will be in DROTHER state. No election should take place unless a DR/BDR is lost.

[Richard Burts]

It is correct that when a third router joins the network and there is already a DR elected and a BDR elected there is not a new election by default.

If you want to cause an election there are several things that you can do to cause a new election. Most of them are disruptive (such as shut down the interface of the Dr or of the BDr, leave it down long enough for the other routers to notice that it is no longer available, so they hold an election). The non-disruptive thing that you can do it to set the OSPF priority of the DR or of the BDR to zero. It will stop being DR or BDR, and a new election is held. After the election you can restore the original priority to the router interface which you set to zero.

You can do these things if you want. Do you really care which router is the DR and BDR? In my experience controlling which router is the DR and which the BDR is a level of micromanagement of the network which I would just as soon not do.

HTH

Rick

[wiztech]

Is there a timer in OSPF that after it expires forces an election?

[Richard Burts]

No there is not a timer that will force an election for DR/BDR.

HTH

Rick

[nstringf]

There is no timer to force an election. An election occurs as mention before if current DR/BDR lost/non-existent.

[minnesotapat]

This was helpful. Thank you. I ended up taking down the interface since we were using a cost statement on the interface and it wouldn't let me go to zero.

[asd_asd_22]

when you add a new router election will not take place, and if for any reason the DR fail the BDR becomes DR and an election take place to select new BDR, and if you need to make new election you must first stop all ospf processes in all the routers and then start it again, but be carefull and start first the process in the router most likely become the DR, because sometimes the first router that become online will be the DR.