MPLS Label Decoder
Decode or build a 32-bit MPLS label stack entry: 20-bit label, Traffic Class (TC/EXP), bottom-of-stack bit, and TTL, with reserved-label names.
This tool handles input and primary processing in your browser and is designed not to send the input to QuickKit’s server.
Fields
| Label (decimal) | — |
|---|---|
| Label (hex) | — |
| Reserved label | — |
| Traffic Class (TC) | — |
| S — bottom of stack | — |
| TTL | — |
| Entry (hex) | — |
| Entry (decimal) | — |
| Entry (binary: label / TC / S / TTL) | — |
How it works
An MPLS label stack entry (RFC 3032) is 32 bits: a 20-bit label, a 3-bit Traffic Class field (the TC field — RFC 5462 renamed it from EXP), the 1-bit S (bottom-of-stack) flag, and an 8-bit TTL. Decode: choose the input radix (hexadecimal or decimal) and paste the 32-bit entry — a bare value such as 12345678 is valid as both, so the radix is stated rather than guessed. Hex input may carry a leading 0x and internal spaces or underscores. Encode: enter the label (0–1048575), TC (0–7), the S bit, and TTL to build the word. Label values 0–15 are special-purpose and are named from the IANA Special-Purpose MPLS Label Values registry (0 IPv4 Explicit NULL, 1 Router Alert, 2 IPv6 Explicit NULL, 3 Implicit NULL, 4 MPLS Network Actions, 7 Entropy Label Indicator, 13 GAL, 14 OAM Alert, 15 Extension Label; 5–6 and 8–12 are unassigned). Labels 16 and above are usable, though a platform may reserve some of the low range for its own use. This decodes one entry only; it does not walk a stack or the payload after it.