What command is used to configure the access VLAN that is associated with an interface?

The command used to configure the access VLAN associated with an interface is "switchport access vlan vlan-id." This command is fundamental in Cisco networking because it enables the network administrator to assign a specific VLAN to an interface that operates in access mode, which handles traffic for a single VLAN only.

When an interface is configured as an access port, it cannot handle traffic from multiple VLANs; thus, isolating it to the defined VLAN improves network management and segmentation. The syntax of the command directly indicates that the interface is being set to operate in a specific VLAN by referencing the "access" parameter alongside the desired VLAN ID.

This precise configuration is critical in scenarios where devices connected to the switch’s access ports need to communicate within the same VLAN, ensuring proper segregation of traffic and enhancing security measures.

The other options do not specify the correct command format recognizable in Cisco devices or do not reflect proper syntax. For instance, "config vlan vlan-id" suggests a command for VLAN configuration in a different context, while "set vlan id vlan-id" and "access vlan vlan-id" do not conform to established command conventions in Cisco IOS.