A subinterface is a logical interface created on a single physical router interface that allows routing between VLANs (known as Router-on-a-Stick (ROAS)). This method is commonly used when only one physical router is available, allowing inter-VLAN communication without additional hardware.
*Why not the other options?
*VXLAN (B) - This is used for extending Layer 2 networks over a Layer 3 infrastructure, primarily in data centers. It does not directly enable inter-VLAN communication.
*Layer 3 switch (C) - A Layer 3 switch can route between VLANs, but the scenario states that purchasing additional hardware is not an option.
*VIR (D) - This is not a standard networking term in the context of VLAN communication.

*Since this issue occurred after a configuration change on a Layer 3 switch, the most likely cause is misconfigured ACLs (Access Control Lists).
*ACLs control which traffic is allowed or denied, so an incorrect ACL may be blocking access to the file server.
*Why not the other options?
*Switching loop (B): A switching loop occurs at Layer 2 (not Layer 3) and causes network-wide broadcast storms, not just loss of access to a file server.
*Duplicate IP addresses (C): This would cause connectivity issues for the devices with the conflict, but not necessarily prevent all users from accessing the file server.
*Wrong default route (D): The default route is used for traffic leaving the local network. If users are unable to access an internal file server, this is unlikely to be the issue.

Comprehensive and Detailed Explanation:
To monitorserver availability,SNMP trapsare the best choice. SNMP (Simple Network Management Protocol) allows devices to send alerts (traps) when certain conditions are met, such as server downtime or high resource usage.
Breakdown of Options:
* A. Packet capture- Capturing packets provides insights into network traffic but doesnot actively monitor server availability.
* B. Data usage reports- Theseanalyze network traffic consumptionbut do not indicate whether a server is available or not.
* C. SNMP traps-Correct answer.SNMP traps notify administrators of server issues inreal time.
* D. Configuration monitoring- This tracksconfiguration changesrather than availability.

Port mirroring, also known as SPAN (Switched Port Analyzer), is used to send a copy of network packets seen on one switch port (or an entire VLAN) to another port where the IDS is connected. This allows the IDS to passively inspect network traffic without interfering with the actual traffic flow. Port mirroring is an essential feature for implementing IDS in a network for traffic analysis and security monitoring.References:
CompTIA Network+ study materials.

See the answer and solution below: