Hi Mitesh,
OSPF and EIGRP are internal routing protocols and they use Multicast address for communication.
In BGP links has to be manually made up.
OSPF
OSPF is classless and converges fairly quickly, using cost as it’s metric. A router running OSPF creates its own database which contains information on the entire OSPF network, not simply neighbor’s routes like EIGRP. This allows the router to make intelligent choices about path selection on its own instead of relying exclusively on neighbor information.
OSPF routers do form neighbor relationships though. They exchange hellos with neighboring routers and in the process learn their neighbor’s Router ID (RID) and cost. Those values are then sent to the adjacency table.
Every router is responsible for computing its own best paths to all destinations within an OSPF domain. Once the SPF algorithm selects the best paths, they are then eligible to be added to the routing table.
EIGRP
Fast Convergence
EIGRP uses the DUAL algorithm to converge very quickly. It does this by knowing neighbor router’s routing tables and predefining primary and secondary routes to every destination network.
Triggered Updates
EIGRP uses partial triggered updates to its directly connected neighbors rather than periodically sharing its entire routing table. This saves link bandwidth because updates are only sent if a change is incurred, only the changes are sent in the update, and lastly – the updates are only sent to a routers’s affected neighbors. Very efficient!
Protocol Independent
Enhanced Interior Gateway Routing Protocol supports more than just IPv4. It supports IPv4, IPv6, IPX, and AppleTalk.
Multicast
EIGRP sends route updates, hellos, and queries to its neighbors using the multicast address 224.0.0.10 so end hosts are not affected. Hellos are sent out every 5 seconds by default to learn about new neighbors and make sure existing neighbors are still available.
Regards,
Gurudath K S
