EIGRP multicast / Acknowledge

kpjunglekpjungle Member Posts: 426
in CCNP
Hi,

Can someone shed some light on the validity of these statements:

- Hello packets - Sent as multicasts, do not require ACK.
- Query = Sent as multicast, require ACK.
- Reply = Sent as unicast, require ACK.
- Update = These can be sent as unicast and multicast, but not 100% sure when what is used, also require ACK.
- ACK - Sent as unicast, do not require ACK (ofcourse :))

Maybe someone can help out?

Thanks!
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  • PlazmaPlazma Member Posts: 503
    kpjungle wrote:
    Hi,

    Can someone shed some light on the validity of these statements:

    - Hello packets - Sent as multicasts, do not require ACK.
    - Query = Sent as multicast, require ACK.
    - Reply = Sent as unicast, require ACK.
    - Update = These can be sent as unicast and multicast, but not 100% sure when what is used, also require ACK.
    - ACK - Sent as unicast, do not require ACK (ofcourse :))

    Maybe someone can help out?

    Thanks!

    Looks pretty accurate.. if more than one router requests the update then the update message is multicast, otherwise I believe it gets by with sending a unicast update.
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  • kpjunglekpjungle Member Posts: 426
    Plazma wrote:
    kpjungle wrote:
    Hi,

    Can someone shed some light on the validity of these statements:

    - Hello packets - Sent as multicasts, do not require ACK.
    - Query = Sent as multicast, require ACK.
    - Reply = Sent as unicast, require ACK.
    - Update = These can be sent as unicast and multicast, but not 100% sure when what is used, also require ACK.
    - ACK - Sent as unicast, do not require ACK (ofcourse :))

    Maybe someone can help out?

    Thanks!

    Looks pretty accurate.. if more than one router requests the update then the update message is multicast, otherwise I believe it gets by with sending a unicast update.

    Request? afaik the update is sent by the router when it detects a network change, and the reply is sent in response to a query, no?
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  • networker050184networker050184 Mod Posts: 11,962 Mod
    Cisco wrote:
    Updates are used to convey reachability of destinations. When a new neighbor is discovered, update packets are sent so the neighbor can build up its topology table. In this case, update packets are unicast. In other cases, such as a link cost change, updates are multicast. Updates are always transmitted reliably.

    As you can read above, if the update is to multiple routers, as in a change to the network, it is multicast. Updates to a single router, as when a router first comes on line, are unicast.

    Source = Introduction to EIGRP
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  • kpjunglekpjungle Member Posts: 426
    Thanks guys :)
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  • networker050184networker050184 Mod Posts: 11,962 Mod
    When I get confused I just head to the Cisco Documentation. There is more than enough info there to answer any of your questions!
    An expert is a man who has made all the mistakes which can be made.
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  • kpjunglekpjungle Member Posts: 426
    networker050184 wrote:
    When I get confused I just head to the Cisco Documentation. There is more than enough info there to answer any of your questions!

    Yeah, ive read alot over there, but sometimes its hard to sift through it all...
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