STP Bridge ID Encoder / Decoder
Encode and decode an 802.1D / 802.1t Spanning Tree Bridge ID: priority field, 4-bit priority, 12-bit extended system ID, and bridge MAC — with a root-election comparison.
This tool handles input and primary processing in your browser and is designed not to send the input to QuickKit’s server.
Bridge ID fields
| Bridge ID (8 bytes, hex) | — |
|---|---|
| Bridge ID (dotted) | — |
| Priority field (16-bit) | — |
| Priority (4-bit × 4096) | — |
| Extended system ID (12-bit) | — |
| Bridge MAC | — |
| Bridge MAC (Cisco dotted) | — |
| Priority field is a multiple of 4096 | — |
| Default priority (32768) | — |
| Root election winner | — |
| Reason | — |
How it works
Two directions. Decode: paste a Bridge ID as 32768.0000.0c12.3456 (decimal priority + Cisco MAC), 8000.001a.2b3c.4d5e (hex priority + MAC, the dotted PPPP.MMMM.MMMM.MMMM form), a plain 16-hex-digit string, a priority:MAC / priority MAC form, or a bare MAC (the priority then defaults to 32768). It reports the raw 8 bytes, the 16-bit priority field (decimal + hex), the 4-bit priority component (always a multiple of 4096), the 12-bit extended system ID (which normally equals the VLAN ID for PVST+/RPVST+ or the MST instance ID), the normalized MAC, whether the priority field is itself a multiple of 4096 (i.e. no extended system ID), and whether the priority is the default 32768. Encode: enter a priority as a multiple of 4096 (0, 4096, … 61440), an extended system ID / VLAN (0–4095) and a MAC; the stored 16-bit value is priority + extendedSystemId. Comparison: fill the optional second Bridge ID to see which one wins the STP root election — the full 8-byte ID is compared, priority field first, then MAC, and the lower ID wins. Ambiguity note: in the dotted 8-byte form the first group is read as hexadecimal (8000 = 0x8000 = 32768); in the priority:MAC form the priority is read as decimal unless written as 0x…. This does not parse BPDU frames — it works on the Bridge ID field only.