Working TCP/IP fundamentals — can explain what a subnet mask, gateway, DHCP scope, DNS resolution and a default route actually do, and troubleshoot with ping, tracert/traceroute, ipconfig/ip a, and nslookup/dig.
Hands-on configuration of at least a few of: router/firewall, managed switch, VLANs, wireless access points, VPN.
Comfort at a command line — Windows and at least basic Linux, and SSH into a device.
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