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Which THREE of the following are characteristics of IPv6? (Select exactly three.)
IPv6 was designed with enough address space to avoid NAT.
A technician needs to verify the IP address of a remote server using DNS. Which command should be used on a Cisco IOS device?
Performs DNS lookup and returns IP address.
Why this answer
The `nslookup` command is used to query DNS servers to resolve a hostname to an IP address. On a Cisco IOS device, `nslookup` sends a DNS query for the specified hostname and returns the corresponding IP address, making it the correct tool for verifying a remote server's IP via DNS.
Exam trap
Cisco often tests the distinction between commands that incidentally perform DNS resolution (like `ping` or `traceroute`) and commands specifically designed for DNS queries (`nslookup`), leading candidates to choose `ping` because it shows the resolved IP in its output.
How to eliminate wrong answers
Option A is wrong because `traceroute` is used to trace the network path to a destination, not to perform DNS resolution; it may trigger a DNS lookup for display but does not directly verify the IP address. Option B is wrong because `show hosts` displays the static hostname-to-address mappings configured locally on the device, not dynamic DNS query results. Option C is wrong because `ping` sends ICMP echo requests to test reachability and may perform a DNS lookup as a side effect, but its primary purpose is not to verify the IP address via DNS.
An engineer configures a trunk port as shown. A device connected to this port sends an untagged frame. Which VLAN will the switch associate the frame with?
Untagged frames are placed in native VLAN.
Why this answer
The switchport trunk native vlan 99 command configures VLAN 99 as the native VLAN for the trunk port. When an untagged frame arrives on a trunk port, the switch associates it with the native VLAN. Therefore, the frame is placed into VLAN 99.
Exam trap
Cisco often tests the misconception that untagged frames on a trunk are dropped or that the native VLAN is always VLAN 1, leading candidates to overlook the explicit native VLAN configuration.
How to eliminate wrong answers
Option A is wrong because VLAN 1 is the default native VLAN only if no native VLAN is explicitly configured; here VLAN 99 is set as the native VLAN. Option B is wrong because untagged frames on a trunk port are not dropped; they are assigned to the native VLAN. Option C is wrong because VLAN 10 is not the native VLAN; the native VLAN is explicitly set to VLAN 99.
A network engineer notices that after a link failure, traffic to a server on a different VLAN is intermittent. The network uses Rapid PVST+. The switch connecting the server is a root bridge for that VLAN. What is the most likely cause of the intermittent connectivity?
Non-edge ports go through STP states, causing delays.
Why this answer
When a link fails in a Rapid PVST+ network, the switch that is the root bridge for the VLAN must reconverge. If the server port is not configured as an edge port (using the 'spanning-tree portfast' command), the switch will transition the port through the listening and learning states (even with Rapid PVST+, non-edge ports still undergo a brief convergence delay). This delay causes intermittent connectivity until the port reaches the forwarding state.
Exam trap
Cisco often tests the misconception that Rapid PVST+ eliminates all convergence delays, but the trap here is that non-edge ports still require a brief transition delay, and candidates may forget that PortFast (edge port configuration) is necessary to avoid this delay for host-facing ports.
How to eliminate wrong answers
Option B is wrong because BPDUs are sent by switches, not servers; a server sending BPDUs with a higher priority would not affect STP convergence, and servers typically do not participate in STP. Option C is wrong because a root bridge flapping due to a configuration mismatch would cause repeated topology changes, but the scenario describes a single link failure followed by intermittent connectivity, not continuous flapping. Option D is wrong because OSPF is a Layer 3 routing protocol and does not affect Layer 2 STP convergence; the issue is within the same VLAN, and OSPF hold-down timers are irrelevant to Rapid PVST+ behavior.
An IPv6-enabled host is trying to discover the MAC address of another host on the same link. The host knows the destination IPv6 address but does not have a corresponding entry in the neighbor cache. Which protocol and message type does the host use?
NS is used for address resolution.
Why this answer
Neighbor Solicitation (NS) is used in IPv6 for address resolution, similar to ARP in IPv4. It is an ICMPv6 message of type 135. Option A is wrong because Neighbor Advertisement (NA) is the reply.
Option B is wrong because Router Solicitation (RS) is for discovering routers. Option D is wrong because ARP is not used in IPv6.
An engineer is troubleshooting packet loss between two hosts on different subnets. The traceroute shows that packets reach the first hop router but then stop. The router's ARP table shows an incomplete entry for the next-hop IP address. What is the most likely cause?
If the next-hop device is offline, the router cannot complete ARP.
Why this answer
An incomplete ARP entry means the router sent an ARP request but received no reply, indicating the next-hop device is unreachable at Layer 2. Option A is wrong because ACL would drop packets differently. Option B is wrong because MTU issues cause fragmentation or drops, not ARP failure.
Option C is wrong because routing protocol convergence would not cause ARP failure specifically.
A network engineer is troubleshooting a connectivity issue between two hosts in different VLANs on the same switch. The hosts are in VLAN 10 and VLAN 20, respectively. The switch has an SVI for each VLAN and IP routing is enabled. Which command should be used to verify that the switch is forwarding traffic between the VLANs?
Displays the routing table, confirming inter-VLAN routing.
Why this answer
Option C is correct because 'show ip route' displays the switch's routing table, which contains the directly connected subnets for VLAN 10 and VLAN 20 (via their SVIs) and any learned routes. Since IP routing is enabled, the switch uses this table to make forwarding decisions between VLANs. Verifying that both VLAN subnets appear in the routing table confirms that the switch can route traffic between them.
How to eliminate wrong answers
Option A is wrong because 'show interfaces trunk' only displays trunk link status and allowed VLANs on trunk ports, not the routing table or inter-VLAN forwarding capability. Option B is wrong because 'show vlan' lists VLAN membership and ports assigned to each VLAN, but does not show Layer 3 routing information or whether the switch is actually routing between VLANs. Option D is wrong because 'show mac address-table' shows Layer 2 MAC address forwarding entries, which are irrelevant for verifying Layer 3 inter-VLAN routing.
Which THREE factors influence the convergence time of OSPF in a large enterprise network? (Choose three.)
SPF computation time affects convergence.
Why this answer
CPU processing power for SPF calculations directly affects convergence time because OSPF must run the Dijkstra algorithm to compute the shortest path tree after a topology change. In large networks with many routers and LSAs, a slower CPU increases the time to complete SPF, delaying route convergence.
Exam trap
Cisco often tests the distinction between failure detection mechanisms (like BFD or Hello timers) and actual convergence processes (SPF calculation and LSA propagation), so candidates may mistakenly think BFD directly reduces convergence time rather than just detection time.
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