200-301 CCNA practice questions: IP Connectivity

C is correct. Topic 3.3.c. A host route uses a full 32-bit mask, 255.255.255.255, so only the exact address matches. Because forwarding prefers the longest matching prefix, a /32 entry always wins over the /24, the /16 or the default route that also cover the address, which is what makes host routes the standard way to steer traffic for one server or to blackhole one address by pointing it at Null0. The same mechanism produces the L entries a router creates for its own interface addresses.
↗ Cisco 200-301 CCNA v1.1 Exam Topics — Section 3: IP Connectivity

A is correct. Topic 3.1.g. The asterisk on the S* entry marks a candidate default, and the next hop it names is what Cisco prints as the gateway of last resort. The role of that entry is defined by when it is used rather than by what it points at: it covers every destination, so it is the entry of last resort and is consulted only once every more specific entry in the table has failed to cover the address. The first packet in this scenario is covered by the OSPF entry for 10.9.9.0/24, so it leaves toward 10.1.1.2 on GigabitEthernet0/0 and the default plays no part. The second is covered by no connected, local or OSPF entry at all, so the default is what keeps it alive; without that entry R1 would have nothing to match and would discard it. That is the practical value of a gateway of last resort on a branch router: it is the single entry that lets the router carry everything it has not been told about toward somebody who has been.
↗ Cisco 200-301 CCNA v1.1 Exam Topics — Section 3: IP Connectivity

A is correct. Topic 3.2.b. Cisco publishes one default administrative distance per source of routing information, and the three in play here are OSPF at 110, RIP at 120 and external EIGRP at 170. The same table separates internal EIGRP at 90 from external EIGRP at 170, which is the trap in this item: a prefix that was redistributed into EIGRP is advertised as external and is not trusted at the internal level. When several protocols offer the same prefix at the same moment, the router ranks the sources by that value, installs the route from the most trusted one and leaves the prefix with the other two inside their own protocol databases, where it reappears in the table if the winning source goes away. The metrics never enter this comparison: a RIP hop count, an OSPF cost and an EIGRP composite metric come from unrelated formulas and mean something only inside their own protocol.
↗ Cisco 200-301 CCNA v1.1 Exam Topics — Section 3: IP Connectivity

A is correct. Topic 3.3.b. Cisco's note on next-hop configuration states that when the next hop of a static route points to an interface, the router considers each of the hosts within the range of the route to be directly connected through that interface and therefore sends ARP requests to any destination addresses that route through the static route, which can cause high processor use and a very large ARP cache along with memory allocation failures. The recommendation on Ethernet is to specify both the outbound interface and the next-hop IP address; on point-to-point links the next-hop address is not needed because there is only one possible neighbor.
↗ Cisco 200-301 CCNA v1.1 Exam Topics — Section 3: IP Connectivity

A is correct. Topic 3.4.a. The show ip ospf interface output prints several values per interface, and only some of them are carried in the hello packet and checked between neighbors: the area, the network type and the Timer intervals configured line with Hello and Dead. Cisco's OSPF configuration guide states that hello and dead intervals must be consistent across all routers on an attached network, with defaults of 10 and 40 seconds on broadcast segments, and a router that receives a hello whose interval fields do not match its own discards it, so no neighbor is ever created and the neighbor table stays empty. The cost and the retransmit interval printed alongside them are local values: they change how this router computes its tree and how long it waits before resending an update, and two routers may hold different values for both and still become fully adjacent. The identical DR state on both sides is the tell-tale of the failure, not its cause, because a router with no neighbors elects itself.
↗ Cisco 200-301 CCNA v1.1 Exam Topics — Section 3: IP Connectivity