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Multicasting Address

Once the DR and BDR have been elected, the other routers (known as DRothers) will establish

adjacencies with the DR and BDR only. All routers continue to multicast Hellos to the AllSPFRouters

address so that they can track neighbors, but DRothers multicast update packets to the

AllDRouters address Only the DR and BDR will listen to this address; in turn, the DR will

flood the updates to the DRothers on

                              reference: TCP/IP routing by jhef doyle

I didn't understand this, what these addressess are? I know these are used for multicasting but how can i see these address in routers?


Sulaiman Ejaz

  • WAN Routing and Switching

Multicasting Address

Hi Sulaiman,

There are two multicast addresses used for ospf routing. used to send/receive hello packets among ospf routers.

If you have a network with DR/BDR the non DR routers send all their updates to and then they get replicated to the others by sending it to is only elected on broadcast/non broadcast network type.

In short these are the address OSPF uses in order to send Hello packets. These are not configurational parameters rather these are standard address used by OSPF protocol.

You could verify which address OSPF is sending the updated using "debug ip ospf events" as below

R1#debug ip ospf events

*Mar  1 00:28:46.891: OSPF: Send hello to area 0 on FastEthernet0/0 from
*Mar  1 00:28:48.579: OSPF: Rcv hello from area 0 from FastEthernet0/0
*Mar  1 00:28:48.583: OSPF: End of hello processing
*Mar  1 00:28:53.467: OSPF: Rcv hello from area 0 from FastEthernet0/0
*Mar  1 00:28:53.471: OSPF: End of hello processing
*Mar  1 00:28:56.103: OSPF: Send hello to area 0 on FastEthernet0/0 from

Hope that helps.



Please rate when applicable or helpful !!!

Re: Multicasting Address


some addititional information to Najaf's posting:

If the media of an OSPF interface is not broadcast-capable, OSPF traffic has to be send to unicast destinations, which have to be configured since the router cannot know them.

The advantage of Multicast is that the interface needs to send only 1 packet to reach multiple destinations of a multiaccess-network and there are no neighbor-statement needed; in other words: Automatic neighbor discovery.

Like the multicast addresses of other routing- and control-protocols, OSPF's AllSPFRouters and AllDRouters addresses belong to the Local Network Control Block

The usage of this addresses is part of the implementation, it depends on the network type if they are used for OSPF communication or unicast instead.

Hope that helps


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