EIGRP multicast / Acknowledge

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!

Find more posts tagged with

Save $250 on 2025 certification boot camps from Infosec!

Book now with code EOY2025

Button

Comments

Plazma

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.

kpjungle

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?

networker050184

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

kpjungle

Thanks guys

networker050184

When I get confused I just head to the Cisco Documentation. There is more than enough info there to answer any of your questions!

kpjungle

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...