Network Toolkit

CIDR summarization, VLSM planning, ACL wildcard building, MAC and EUI-64 conversion, and BGP regex testing combined on one page.

Five networking utilities on one page. Pick a tab, everything runs in your browser and nothing is sent to any server.

CIDR Summarizer

Paste prefixes, addresses, or ranges (any mix of IPv4 and IPv6, separated by spaces, commas, or new lines) and get the minimal exact aggregate set plus the single covering supernet.

Prefixes to summarize

Try:

VLSM Planner

Give a parent block and the host count each subnet needs, one requirement per line as name hosts (the name is optional). Subnets are allocated largest first with no overlaps, the standard VLSM method.

Parent block Required subnets (name hosts)

Try:

Free space remaining

ACL Wildcard Helper

Build Cisco wildcard masks three ways. Convert a prefix, expand an arbitrary range into the fewest ACL lines, or squeeze a set of same-size networks into a single non-contiguous wildcard.

Prefix to wildcard Range to ACL lines Set to one wildcard

Prefix (address/length or address mask)

Address range

Networks to match (one per line, same prefix length)

Try:

ACL lines

MAC Address Tool

Paste a MAC address in any common format. The tool normalizes it, decodes the I/G and U/L bits, and derives the modified EUI-64 interface ID with its link-local and optional SLAAC address.

MAC address IPv6 prefix for SLAAC (optional, /64)

Try:

BGP Regex Tester

Test Cisco-style AS-path regular expressions or IPv4 prefix-lists against your own sample data, with a live verdict per line. In AS-path mode the Cisco underscore is supported and matches a space, comma, brace, parenthesis, or the start or end of the path.

AS-path regex Prefix-list

AS-path regex AS paths to test (one per line)

Common:

Prefix-list rules (first match wins, implicit deny at the end) Prefixes to test (one per line)

Try:

Notes on the Methods

The CIDR summarizer merges overlapping and adjacent ranges first, then emits the fewest exact prefixes for each merged range, so the aggregate list never covers an address you did not enter. The single supernet is the smallest one prefix that contains everything and reports how many extra addresses it pulls in.

The VLSM planner sizes each subnet to the smallest power of two that fits the requested hosts plus network and broadcast addresses, allocates largest first (the standard method that avoids fragmentation), and lists the remaining free blocks as CIDR prefixes.

In the ACL helper, the set mode ANDs the network addresses to find the common base and ORs the differing bits into the wildcard. A single wildcard line matches exactly a power of two networks, so the tool tells you when the line would also match networks you did not list.

The prefix-list tester follows Cisco semantics. Without ge or le the prefix length must match exactly, ge and le bound the length range, evaluation stops at the first matching rule, and an implicit deny sits at the end.