Cisco CCNA (200-301) — All Questions

A router has two routes to 10.1.1.0/24: a static route with administrative distance 1 and an OSPF route with AD 110. Which route is installed in the routing table?

• a.The OSPF route, because OSPF is dynamic
• b.The static route, because it has the lower AD✓
• c.Both routes, load-balanced equally
• d.Neither, they conflict and both are rejected

Administrative distance measures the trustworthiness of a routing source, and the route with the lower AD is preferred. A static route (AD 1) is preferred over an OSPF route (AD 110) to the same destination. The less-trusted OSPF route is kept in the OSPF database but not installed while the static route is valid.

Which command correctly configures a default static route that forwards all unknown-destination traffic to next-hop 203.0.113.1?

• a.ip route 203.0.113.1 0.0.0.0 0.0.0.0
• b.ip route 203.0.113.1 255.255.255.255 0.0.0.0
• c.ip route 0.0.0.0 0.0.0.0 203.0.113.1✓
• d.ip default-gateway 203.0.113.1

A default route uses 0.0.0.0 0.0.0.0 to match any destination, followed by the next-hop address, so 'ip route 0.0.0.0 0.0.0.0 203.0.113.1' is correct. It is the gateway of last resort used when no more specific route matches. The 'ip default-gateway' command only applies to a device that is not routing (ip routing disabled).

In OSPFv2, two routers on the same Ethernet segment fail to form an adjacency. Which mismatch is a common cause?

• a.Different hello/dead timers or mismatched area IDs✓
• b.Different hostnames
• c.Different interface descriptions
• d.Different serial numbers

OSPF neighbors must agree on parameters including hello and dead intervals, area ID, authentication, subnet mask, and MTU to reach the FULL adjacency state. A mismatch in any of these prevents the neighbor relationship from forming. Hostnames and descriptions are cosmetic and do not affect adjacency.

What metric does OSPF use by default to calculate the cost of a link?

• a.Hop count
• b.Delay
• c.Load
• d.Bandwidth (reference bandwidth / interface bandwidth)✓

OSPF calculates cost based on bandwidth, using the formula reference bandwidth (default 100 Mbps) divided by the interface bandwidth. Higher-bandwidth links receive lower costs and are preferred. Because modern links exceed the default reference, engineers often raise the reference bandwidth so faster interfaces are distinguished.

A packet arrives at a router destined for 192.168.5.130. The routing table contains 192.168.5.0/24, 192.168.5.128/25, and 0.0.0.0/0. Which route is used?

• a.192.168.5.0/24
• b.192.168.5.128/25✓
• c.0.0.0.0/0
• d.All three simultaneously

Routers forward using the longest prefix match, meaning the most specific route (the one with the longest matching subnet mask) wins. 192.168.5.130 falls within 192.168.5.128/25 (128-255 range), which is more specific than the /24 or the default route. Longer masks always take precedence regardless of administrative distance across differing prefixes.

Which statement about IPv6 Stateless Address Autoconfiguration (SLAAC) is correct?

• a.It requires a DHCPv6 server to assign every address
• b.It uses ARP to learn the gateway
• c.Hosts build their own address from the Router Advertisement prefix✓
• d.It only works with link-local addresses

With SLAAC, a host listens for Router Advertisement messages, takes the announced /64 prefix, and combines it with a self-generated interface identifier to form a global address without a DHCP server. Neighbor Discovery Protocol (not ARP) provides address resolution and router discovery in IPv6. DHCPv6 is optional and can supplement SLAAC for information like DNS.