Subnet in seconds, then study the 200-301 in the order the exam weights it.

Domain 1.0 is 20% of the CCNA 200-301 and is where subnetting lives. It covers the roles of routers, switches, firewalls, access points and controllers; two-tier, three-tier, spine-leaf and WAN topologies; copper and fiber cabling and how to spot duplex, speed and collision problems; TCP versus UDP; IPv4 addressing and subnetting; IPv6 address types; wireless principles; virtualization; and switching concepts such as MAC learning and aging.

Domain 2.0 is 20% of the CCNA and covers Layer 2 access — VLANs spanning multiple switches, access ports, the default and native VLAN, 802.1Q trunks, Layer 2 discovery (CDP/LLDP), Layer 2/3 EtherChannel with LACP, Rapid PVST+ root bridge election and port roles, PortFast, Cisco wireless architectures and AP modes, WLC management access, and configuring a WLAN with WPA2 PSK from the GUI.

Domain 3.0 is the largest CCNA domain at 25%. It covers reading a routing table (code, prefix, mask, next hop, AD, metric, gateway of last resort), how a router chooses a route (longest prefix match first, then administrative distance, then metric), configuring IPv4 and IPv6 static routes (default, network, host, floating), single-area OSPFv2 (neighbor adjacencies, point-to-point vs broadcast, router ID, DR/BDR), and the purpose of first-hop redundancy protocols.

Domain 4.0 is 10% of the CCNA. It covers inside source NAT with static entries and pools, NTP client/server mode, the roles of DHCP and DNS, SNMP, syslog features and severity levels, configuring a DHCP client and relay agent, QoS forwarding per-hop behavior (classification, marking, queuing, policing, shaping), remote access with SSH, and the roles of TFTP and FTP.

Domain 5.0 is 15% of the CCNA. It covers security concepts (threats, vulnerabilities, exploits, mitigation), the security program elements, device access control with local passwords, password policy elements, IPsec remote-access and site-to-site VPN concepts, configuring and verifying standard and extended IPv4 access lists, Layer 2 security (DHCP snooping, dynamic ARP inspection, port security), AAA concepts, wireless security protocols and WPA2/WPA3 PSK configuration.

Domain 6.0 is 10% of the CCNA 200-301 v1.1. It covers how automation affects network management, controller-based versus traditional networking, software-defined architectures (overlay, underlay, fabric; separation of control and data planes; northbound and southbound APIs), Cisco DNA Center versus traditional campus management, REST API characteristics (CRUD, HTTP verbs, encoding), Ansible and Terraform, JSON, and — new in v1.1 — generative and predictive AI concepts.

Enter any IPv4 address with a prefix or mask and get the network and broadcast addresses, usable host range, host count, wildcard mask, class and RFC 1918 status, with the binary shown.

Give it a base network and the hosts each subnet needs; it allocates largest-first, non-overlapping subnets with network, mask, usable range and broadcast for each, exactly as a CCNA VLSM question expects.