Explanation/Reference:
Section: Addressing and Routing Protocols in an Existing Network Explanation Explanation:
Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF) can operate on non-broadcast multi-access (NBMA) point-to-point networks and NBMA point-to-multipoint networks.
Because NBMA networks, such as Frame Relay and Asynchronous Transfer Mode (ATM), do not support Data Link layer broadcasts, routing protocols that operate on NBMA networks must support methods of neighbor discovery and route advertisement that do not rely on multicast or broadcast transmission methods. Although subinterfaces can be used to treat an NBMA point-to-multipoint network as a series of point-to-point connections, you are not required to configure subinterfaces for NBMA point-to-multipoint networks with EIGRP and OSPF.
EIGRP, not OSPF, performs automatic route summarization. Summarization is a method that can be used to advertise a group of contiguous networks as a single route. You can configure a router to summarize its networks on either classful or classless network boundaries. When a router performs summarization, the router advertises a summary route rather than routes to each individual subnetwork, which can cause a routing protocol to converge faster. This can also reduce unnecessary consumption of network bandwidth, because only a single summary route will be advertised by the routing protocol. EIGRP is capable of performing summarization on any EIGRP interface. By contrast, OSPF supports summarization at border routers and redistribution summarization.
OSPF, not EIGRP, uses a designated router (DR) and a backup designated router (BDR) as focal points for routing information. Only the DR distributes link-state advertisements (LSAs) that contain OSPF routing information to all the OSPF routers in the area. A DR and a BDR are elected only on multiaccess networks; they are not elected on point-to-point networks. If the DR fails or is powered off, the BDR takes over for the DR and a new BDR is elected.
Intermediate System-to-Intermediate System (ISIS), not EIGRP or OSPF, uses a designated intermediate system (DIS). A DIS is functionally equivalent to an OSPF DR. The DIS serves as a focal point for the distribution of routing information. Once elected, the DIS must relinquish its duties if another router with a higher priority joins the network. If the DIS is no longer detected on the network, a new DIS is elected based on the priority of the remaining routers on the network segment.
OSPF, not EIGRP, uses areas to limit the flooding of database updates, thereby keeping routing tables small and update traffic low within each area. By contrast, EIGRP uses stub routers to limit EIGRP queries.
An EIGRP stub router advertises only a specified set of routes.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 11, OSPFv2 Summary, p. 439
CCDA 200-310 Official Cert Guide, Chapter 10, EIGRP for IPv4 Summary, p. 406 Cisco: Configuration Notes for the Implementation of EIGRP over Frame Relay and Low Speed Links:
NBMA Interfaces (Frame Relay, X.25, ATM)
Cisco: OSPF Design Guide: Adjacencies on Non-Broadcast Multi-Access (NBMA) Networks