CIDR / Subnet Calculator MCP Server

CIDR / Subnet Calculator

Pure local computation using standard IP math—no outbound requests.

Capabilities

• Subnet analysis: Given a CIDR string (IPv4 or IPv6), get network address, prefix length, netmask, wildcard (host) mask, address counts, first/last usable hosts (IPv4 respects traditional network/broadcast reservation except /31 and /32 point-to-point and host rules), and IPv4 class (A–E). IPv6 responses omit broadcast/class and include the last address in the prefix instead.
• Membership check: Given an IP and a CIDR, determine whether the address is inside the network. When it is, the tool reports the zero-based offset from the network address. IP and network must be the same IP version.

Gotchas

• IPv6 size: Very large prefixes return huge counts as decimal strings when needed so values stay safe for typical JSON consumers.
• Strict version match: Do not mix IPv4 addresses with IPv6 networks (or the reverse).
• Invalid input: Malformed CIDR or IP strings return a clear error; fix the notation and retry.