Which type of address does OSPFv3 use to form neighbor adjacencies and to send LSAs?

Which type of address does OSPFv3 use to form neighbor adjacencies and to send LSAs?
A. unicast IPv6 addresses
B. link-local addresses
C. multicast address FF02::5
D. unicast IPv4 addresses

cisco-exams

14 thoughts on “Which type of address does OSPFv3 use to form neighbor adjacencies and to send LSAs?

  1. Source: Implementing Cisco IP Routing (ROUTE) Foundation Learning Guide: (CCNP ROUTE 300-101)
    Section: OSPF Implementation
    Update destination address: OSPF uses multicast and unicast, rather than broadcast, for sending messages. The IPv4 multicast addresses used for OSPF are 224.0.0.5 to send information to all OSPF routers and 224.0.0.6 to send information to DR/BDR routers. The IPv6 multicast addresses are FF02::5 for all OSPFv3 routers and FF02::6 for all DR/BDR routers.

    If the underlying network does not have broadcast capabilities, you must establish OSPF neighbor relationships using a unicast address. For IPv6, this address will be a link-local IPv6 address.

    The DR/BDR election process takes place on broadcast and NBMA networks. The main difference between the two is the type of IP address used in the Hello packet. On the multiaccess broadcast networks, routers use multicast destination IPv4 address 224.0.0.6 to communicate with the DR (called AllDRRouters), and the DR uses multicast destination IPv4 address 224.0.0.5 to communicate with all other non-DR routers (called AllSPFRouters). On NBMA networks, the DR and adjacent routers communicate using unicast addresses.

    So… the Real question within a question, is which scenario is this question asking about – a broadcast or a NBMA network?
    As the question does not clarify the scenario, one should assume default operation – which is apparently assumed (by Cisco) to be a broadcast network, using Multicast communication for neighborships and LSAs.

    Given that, Answer C, “multicast address FF02::5” is the best choice.
    (unless, of course, the writer of the question and the quality assurance folks that approved this question made the mistake of thinking the answer is B (link-local).
    So… what it comes down to is – what do you believe the person who wrote the question and answer meant for us to choose? Or… you could go the “safe” route (no pun intended) and choose the “best” answer for the way this question is worded, and that would be C (multicast).

    Good luck!

  2. Answer is B.

    Update destination address: OSPF uses multicast and unicast, rather than broadcast, for sending messages. The IPv4 multicast addresses used for OSPF are 224.0.0.5 to send information to all OSPF routers and 224.0.0.6 to send information to DR/BDR routers. The IPv6 multicast addresses are FF02::5 for all OSPFv3 routers and FF02::6
    for all DR/BDR routers. If the underlying network does not have broadcast capabilities, you must establish OSPF neighbor relationships using a unicast address. For IPv6, this address will be a link-local IPv6 address.

    From CCNP Route Foundation Guide

  3. As soon as OSPFv3 is enabled , it sends out OSPFv3 Type 1 Hello messages to the FF02::5 multicast address. Once it receives Hello packets from the neighbor Router, they negotiate the Master/Slave relationship and then start to send DBD packets.

  4. I think the difference here, is whether it’s to form adjacency, or to send routing updates. To form the initial adjacency with it’s neighbor, it uses the link-local address. To send subsequent LSA/Routing updates once the neighborship has been established, it uses the Multicast address. Thoughts?

  5. Answer is B: Link local
    OSPFv3 uses link-local addresses for the neighbor adjacency and sending LSAs.

    networklessons.com

  6. Answer is B: Link local
    OSPFv3 uses link-local addresses for the neighbor adjacency and sending LSAs.

    networklessons.com

  7. Link local address is a special type of address intended for communications within the local network segment or a point-to-point connection. Routers do not forward packets with link local address. The link local address gets a FE80::/10 prefix.

    The OSPFv3 uses Link-local address to form neighbor adjacency by sending and receiving the hello packet to the neighbor router.

    So the answer is B (Link-local addresses)

  8. all, who answer – C. Pls, tell me about multicast address FF02::5 in NMBA, or adjacencies with DR/BDR…

    B – only valid answer!

  9. Adjacency
    Not all neighbors establish adjacency. Depending on the network type and designated router
    establishment, some neighbors become fully adjacent and share LSAs with all their neighbors, while
    other neighbors do not.
    Point-to-point—A network that exists only between two routers. All neighbors on a point-to-point
    network establish adjacency and there is no DR.
    • Broadcast—A network with multiple routers that can communicate over a shared medium that
    allows broadcast traffic, such as Ethernet. OSPFv3 routers establish a DR and BDR that controls
    LSA flooding on the network. OSPFv3 uses the well-known IPv6 multicast addresses, FF02::5, and
    a MAC address of 0100.5300.0005 to communicate with neighbors.
    All other routers establish adjacency with the DR and the BDR and use the IPv6 multicast address
    FF02::6 to send LSA updates to the DR and BDR. Figure 7-1 shows this adjacency relationship between
    all routers and the DR.

  10. Ans:B
    Link local address is a special type of address intended for communications within the local network segment or a point-to-point connection. Routers do not forward packets with link local address. The link local address gets a FE80::/10 prefix.

    The OSPFv3 uses Link-local address to form neighbor adjacency by sending and receiving the hello packet to the neighbor router.

Leave a Reply

Your email address will not be published. Required fields are marked *


The reCAPTCHA verification period has expired. Please reload the page.