Which IPv4 multicast address is specifically for all OSPF Designated Routers including Backup?

The address specifically designated for all OSPF (Open Shortest Path First) Designated Routers, including the Backup Designated Router, is 224.0.0.6. This multicast address is leveraged by OSPF to efficiently send routing updates to these routers within a multicast group.

In OSPF, routers that participate in multi-access networks elect a Designated Router (DR) and a Backup Designated Router (BDR) to minimize the amount of routing information exchanged. The DR is responsible for generating link-state advertisements (LSAs) and disseminating them to other OSPF routers, while the BDR serves as a backup for this role. When OSPF routers send multicast messages to the group of DR and BDR, they use the address 224.0.0.6 to ensure that only those specific routers hear the updates, optimizing the OSPF communication process.

The other addresses mentioned serve different purposes within OSPF or are linked to different aspects of multicast routing. For instance, 224.0.0.9 is used for OSPF routers and sends messages to all OSPF routers but does not distinguish between the DRs and BDRs. Therefore, identifying the correct