A technician is setting up a new wireless router at a client's home. Which of the following would the technician do FIRST when securing the network?

Changing the DHCP scheme is a network configuration preference that does not directly impact security and is not a prerequisite before other security measures.

Wireless routers ship with identical, publicly known default usernames and passwords (such as admin/admin or admin/password). An attacker on the local network can immediately take full control of the router using these credentials. Changing the administrative password before making any other configuration changes prevents unauthorized access to all router settings, making it the mandatory first security action.

Enabling VPN passthrough allows VPN traffic to traverse the router and is a feature configuration, not a foundational security hardening step.

Increasing radio power levels improves wireless coverage but also potentially expands the attack surface and is not related to securing administrative access.