Let me offer a couple of refinements.
>Thanks for all the replies (Expect for abc),
> I do however feel like we have missed the question. I wanted to know if
>IGRP and EIGRP use the same method in discovering networks. Not how or if
>they establish neighbors. I understand that, but that is not how they
>discover networks.
I think it would be really more in keeping with both EIGRP and OSPF
terminology (and ISIS for that matter) to speak of topology discovery
rather than network discovery. True, while a Type 2 LSA is called
"network," the overall term "network" has classful implications that
just confuse things.
>With OSPF neighbor adjacencies are not how it discovers
>networks, it uses LSAs to do that.
Ah...but where do the LSAs come from? On a multiaccess medium, from
the DR to which the router is adjacent. Flooding is another source,
as is local hardware detection.
>I have done a lot of reading on this and
>this is where I am at now:
>
>These are the steps:
>1) Upon startup, a router uses Hellos to discover neighbors and to identify
>itself to neighbors. When a neighbor is discovered, EIGRP will attempt to
>form an adjacency with that neighbor. (This is all done across the multicast
>address 224.0.0.10) This information is stored in the neighbor table. (Ok we
>have established neighbor relationships, but no network information has been
>exchanged)
>NOTE - ABC you said that IGRP uses DV algorithm to establish neighbors, this
>is not true. IGRP does not establish neighbors (no neighbor table). A lot of
>talk from someone who can't even get the facts right.
DV and LS are only parts of the overall routing control process. They
have to be preceded by neighbor discovery and adjacency management.
They are involved with the transfer of topology information and the
computation and selection of best routes.
>
>2) After an adjacency with a neighbor established, the router will receive
>updates from its neighbors. The updates will contain all routes known by
>the sending router. (Plus the metrics - same as IGRP +256)
A refinement -- neither IGRP nor EIGRP send the actual metrics. They
send the components from which metrics are computed (bandwidth,
delay, etc.) so that an individual router can use its own weights to
compute the composite metric.
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=11584&t=11273
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