Solved: DR election in ospf

sarahr202 · ‎08-13-2009

Hi every body.

Let say we have a following scenario

sw(L2)fo/1-------- f0Router

I just configured router with ospf

According to my book, router will wait for " dead interval time" before concluding that it is DR.

How about if i just take the router out of box, configure it for ospf without connecting its interfaces to any switch or network. So we have just stand alone router configured with ospf . Will router still wait for dead interval time and conclude it is indeed a DR.

Thanks a lot.

Richard Burts · ‎08-13-2009

I think we need to be very careful about the question from the original poster. The question asks if you take a router fresh out of the box and configure it for OSPF. If the interface is not connected to anything, then on an IOS router the interface will be line protocol down and in that case OSPF will not be running on the interface and there will be no election.

But the response from Jorgemario is wrong :(

The election of DR does not depend on having neighbors on the multiaccess segment. When the inteface on the IOS router does go to state of protocol up, and with OSPF configured on the interface then the router will initiate the process of election. It will still wait for the interval before it completes the election. But there will be an election. I have seen it many times where there is an Ethernet interface on a router that has no OSPF neighbors and that router is the DR for the segment.

HTH

Rick

HTH

Rick

View solution in original post

jbrenesj · ‎08-13-2009

The DR is "elected" when there are "neighbors" on a multiaccess network segment. So far there are no neighbor relationships so there is nothing to elect. The network belonging to f0 of the rounter won't be active anywhere

Richard Burts · ‎08-13-2009

I think we need to be very careful about the question from the original poster. The question asks if you take a router fresh out of the box and configure it for OSPF. If the interface is not connected to anything, then on an IOS router the interface will be line protocol down and in that case OSPF will not be running on the interface and there will be no election.

But the response from Jorgemario is wrong :(

The election of DR does not depend on having neighbors on the multiaccess segment. When the inteface on the IOS router does go to state of protocol up, and with OSPF configured on the interface then the router will initiate the process of election. It will still wait for the interval before it completes the election. But there will be an election. I have seen it many times where there is an Ethernet interface on a router that has no OSPF neighbors and that router is the DR for the segment.

HTH

Rick

HTH

Rick

sarahr202 · ‎08-13-2009

Thanks Rick

My book also supports your point as well.

Book shows an example where a router is configured for ospf, then it was connected to layer 2 switch which has no other router connected . Router wait for dead interval time before deciding it is the DR on the segment.

thanks