CCIE Security Exam: Troubleshooting OSPF Router Exchange Messages

MAC Address for OSPF Router Exchange Messages

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A network administrator uses a LAN analyzer to troubleshoot OSPF router exchange messages sent to all OSPF routers.

To which one of these MAC addresses are these messages sent?



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A. B. C. D. E. F.


OSPF (Open Shortest Path First) is a routing protocol that uses multicast IP addresses to exchange routing information between routers. OSPF routers use multicast addresses to send and receive OSPF packets, and these addresses map to specific MAC addresses.

The MAC addresses used by OSPF depend on the type of OSPF packet being sent. There are three types of OSPF packets:

  1. Hello packets - used to discover and maintain neighbor relationships
  2. Database Description (DBD) packets - used to exchange information about the contents of the link-state database
  3. Link-state Update (LSU) packets - used to communicate changes to the link-state database

The MAC address used for OSPF packets depends on the type of packet and the destination IP address. Here are the MAC addresses used by each type of OSPF packet:

  • Hello packets: 01-00-5E-00-00-05
  • DBD packets: 01-00-5E-00-00-05
  • LSU packets: 01-00-5E-00-00-05 (for IP multicast addresses and or 01-00-5E-00-00-05 (for all other IP multicast addresses)

Therefore, the answer to the question is B. 01-00-5E-00-00-05, which is the multicast MAC address used by OSPF for Hello and DBD packets.