OSPF & Frame Relay question

jscimeca715 · 07-09-2009, 03:19 PM

I'm currently heading straight towards the INCD2 test at the end of this month and may have a few clarifying questions for everyone. I appreciate all of your guy's awesome help in advance.

Is an OSPF router interface that connects to a Frame Relay switch considered a BROADCAST type OSPF interface or a POINT TO POINT type OSPF interface?

I'm getting mixed messages when I run the simulators and such and would appreciate some clarification.

captobvious · 07-09-2009, 03:30 PM

Quote:

Originally Posted by jscimeca715

I'm currently heading straight towards the INCD2 test at the end of this month and may have a few clarifying questions for everyone. I appreciate all of your guy's awesome help in advance.

Is an OSPF router interface that connects to a Frame Relay switch considered a BROADCAST type OSPF interface or a POINT TO POINT type OSPF interface?

I'm getting mixed messages when I run the simulators and such and would appreciate some clarification.

You have to have it broadcast to get the updates through the frame relay switch.

mrblackmamba343 · 07-09-2009, 07:25 PM

by default OSPF across a frame-relay is known as NBMA non broadcast Multiaccess. It electes a DR and a BDR like broadcast but they are still different since neighbors have to be manualy defined

jscimeca715 · 07-09-2009, 09:10 PM

Quote:

Originally Posted by mrblackmamba343

by default OSPF across a frame-relay is known as NBMA non broadcast Multiaccess. It electes a DR and a BDR like broadcast but they are still different since neighbors have to be manualy defined

So in terms of OSPF neighbor relationships does routers attached to a frame relay switch become fully adjacent with neighbors that aren't dr and bdr?

mrblackmamba343 · 07-10-2009, 12:33 AM

Quote:

Originally Posted by jscimeca715

So in terms of OSPF neighbor relationships does routers attached to a frame relay switch become fully adjacent with neighbors that aren't dr and bdr?

Yes routers can become adjacent with routers that are not either DR or BDR. Even in some instances you might want to prevent the election from taking place by assigning the ospf prioty of 0 to the interface. Assuming you only want a DR and no BDR

ccie15672 · 07-10-2009, 12:48 AM

Frame-relay multipoint interfaces are NBMA interfaces. In a hub and spoke environment, you want the hub to be the DR or you will have issues.

I imagine very few people, perhaps zero, actually use multipoint interfaces. P2P subinterfaces are the way to go.

Dubuku57 · 07-10-2009, 01:47 AM

Quote:

Originally Posted by ccie15672

Frame-relay multipoint interfaces are NBMA interfaces. In a hub and spoke environment, you want the hub to be the DR or you will have issues.

I imagine very few people, perhaps zero, actually use multipoint interfaces. P2P subinterfaces are the way to go.

Arent P2P subinterafaces used to solve the problem of split horizon - which is for DV routing? In this case, if OSPF is used, then that issue wil not exist. Correct me if im wrong, but with P2P there wont be any DR/BDR right?

Dubuku57 · 07-10-2009, 02:00 AM

Quote:

Originally Posted by captobvious

You have to have it broadcast to get the updates through the frame relay switch.

Again pls correct me if im way off, but i doesnt OSPF use multicast addie of 224.0.0.5/6 to send data to the DR and BDR? Or is it only LSA packets every 10 sec?
224.0.0.10 -- EIGRP hello packets every 5 sec
224.0.0.9 -- RIP v2 hello packets every 30 sec

The broadcast parameter needs to be set on the FR encap links to allow the OSPF/EIGRP/RIP updates to get through right?

When the sh ip ospf int command, i do see the Network type: BROADCAST and i know tt adjacent routers are called DROTHERS..but i dun think i get it 100%.. Could anyone crystallise it pls? Thanks!

mrblackmamba343 · 07-10-2009, 01:34 PM

Quote:

Originally Posted by ccie15672

Frame-relay multipoint interfaces are NBMA interfaces. In a hub and spoke environment, you want the hub to be the DR or you will have issues.

I imagine very few people, perhaps zero, actually use multipoint interfaces. P2P subinterfaces are the way to go.

Yea they are but that it not the default network type.

Dubuku57 · 07-11-2009, 01:08 AM

What then is the default FrameRelay Network type? Couldya also pls clarify my doubts above? hehe thankssss