Which tool is most effective for a security administrator to analyze network traffic on a single VLAN used by vendors?

A sniffer is a tool designed specifically to capture and analyze network traffic. In the context of monitoring traffic on a VLAN used by vendors, a sniffer can intercept packets that traverse the network, providing insights into the data flowing to and from devices within that VLAN. This enables a security administrator to examine the contents of packets, identify potential security issues, track usage patterns, monitor for unauthorized access, and troubleshoot network problems.

Using a sniffer, the administrator can determine if any suspicious activity is occurring, such as unauthorized access attempts or the presence of potentially malicious traffic. This capability is essential in maintaining the security and integrity of the network, especially in environments where external vendors may have access to sensitive information.

Other tools mentioned, such as a port scanner, are useful for discovering open ports and services on devices but do not provide the detailed traffic analysis needed for in-depth monitoring or troubleshooting of network communications. Similarly, a cipher is related to the encryption and decryption of data, while a checksum is used to verify data integrity rather than analyze traffic. Therefore, a sniffer is the most effective tool for the specific task of analyzing network traffic within a VLAN.