EIGRP and OSPF clarity

Robbo777Robbo777 Posts: 330Member
Hi, i just wanted some clarity on this summary i have for these 2 protocols and how they function.

So EIGRP is a hybrid distance vector protocol that forms neighbours and forwards their routing table onto their directly connected neighbours.

OSPF, provided that they're all in the same area, forwards its routing table onto all the routers in the area even if they are not directly connected to that specific router.

So basically if there was a big switch and connected to this switch was 20 routers, each router running OSPF, then they would flood the entire switch with its own individual routing table. Whereas if it was 20 routers running EIGRP, then they would only forward their routing tables onto the router next to them?? Or am i totally wrong about that haha?

Thanks for the help everyone on this.


  • networker050184networker050184 Posts: 11,962Mod Mod
    They aren't forwarding their routing tables in either protocol.

    EIGRP uses a topology table to find the best paths and advertises those in updates, certain rules applying of course. Since only best paths are sent each router doesn't actually have a complete view of the network.

    In OSPF every router in an area generates LSAs for it's connected networks. These are flooded throughout the area and each router independently builds it's tree of the network. Every router in the network has a complete view.

    The outcome is fairly similar in that these best routes are then populated into the local routers routing table.
    An expert is a man who has made all the mistakes which can be made.
  • Robbo777Robbo777 Posts: 330Member
    So in my switch example then, how would each protocol go about its duties?

  • james43026james43026 Posts: 303Member
    Well, this would take far too long for me to type out an explanation of how OSPF exchanges LSDB info. So I'll link a great article on the neighbor establishment process. This article explains in more detail how to read the OSPF database and some details on the major LSA types that are used in building the LSDB. This article will help explain how EIGRP will build a topology table.

    Sorry to just throw links at you, but this isn't an easy process to sum up quickly in text. You will just have to take the time to read the fine details in the articles presented.
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