IP Connectivity
Free Cisco Certified Network Associate (CCNA) practice — 6 questions on IP Connectivity, with explanations. No sign-up. Full 12-question mixed test →
A router's IPv4 routing table contains the following entries for a packet destined to 192.168.1.140:
- 192.168.1.0/24 via R1 (OSPF, AD 110)
- 192.168.1.128/25 via R2 (static, AD 1)
- 192.168.1.128/26 via R3 (RIP, AD 120)
- 0.0.0.0/0 via R4 (default route)
Which route does the router actually use to forward this packet?
The router always forwards based on the longest (most specific) matching prefix first, regardless of administrative distance or metric. Since 192.168.1.140 falls within all four routes, the router selects the /26 entry because it is the most specific match. AD and metric only break ties between routes to the identical prefix.
A router learns 172.16.20.0/24 from three sources simultaneously: a static route (AD 1), an OSPF route (AD 110), and a RIP route (AD 120). All three advertise the identical prefix and mask. Which route is installed in the routing table?
When multiple routing sources advertise the exact same destination prefix, the router installs only the route from the source with the lowest administrative distance. Static routes default to AD 1, which beats OSPF (110) and RIP (120).
A network has a primary route to 10.1.1.0/24 learned dynamically via OSPF (AD 110). An administrator wants to configure a floating static route out of Serial0/0/1 that only becomes active if the OSPF route disappears. Which command correctly accomplishes this?
A floating static route must have an administrative distance HIGHER than the primary route's AD so it stays in the background (in the RIB but unused) until the primary route is withdrawn. Since OSPF's AD is 110, an AD of 130 ensures the static route only becomes active if the OSPF route fails.
You need to configure an IPv6 static route to 2001:db8:acad:2::/64 that points out interface GigabitEthernet0/1 using the next-hop link-local address fe80::2. Which command is syntactically correct and functional?
Because link-local IPv6 addresses are not globally routable and are only unique per interface, IOS requires that you specify BOTH the exit interface AND the link-local next-hop address when using a link-local address as the next hop for a static route. The correct syntax order is: prefix, exit-interface, next-hop.
Router R1 has Gi0/0 connected to a LAN of hosts and Gi0/1 connected via a WAN link to R2; both interfaces run OSPF. The administrator configures 'passive-interface GigabitEthernet0/0' under 'router ospf 1'. What is the resulting behavior?
The passive-interface command suppresses OSPF Hello packets on the specified interface only, preventing any neighbor adjacency from forming there — but the interface's connected network is still included in OSPF and advertised as a stub network to other routers.
R1 (HSRP priority 150, preempt enabled) and R2 (HSRP priority 100, default preempt disabled) are configured in HSRP group 5 sharing virtual IP 10.1.1.1. R1 fails and R2 becomes the active router. After R1 recovers and comes back online, what happens?
The 'preempt' keyword allows a router to take over the active role from a lower-priority router at ANY time, not just during the initial election. Since R1 has both preempt enabled and a higher configured priority (150 > 100), it reclaims the active role as soon as it comes back online and its hello messages are received by R2.
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