Vendor fields: name, OUI, PN, SN, date code

The vendor block is what a host shows in show interface transceiver and what its compatibility policy matches against. The specifications define the fields, their lengths and their encoding precisely — and hosts are unforgiving about padding, case and stray bytes. This page collects the rules, the byte ranges per specification and the mistakes that make a perfectly good module read as garbage.

The fields

Field	SFF-8472 (SFP, A0h)	SFF-8636 (QSFP, page 00h)	CMIS (page 00h)	INF-8077i (XFP)	Format
Vendor name	20–35	148–163	129–144	148–163	16 ASCII
Vendor OUI	37–39	165–167	145–147	165–167	3 bytes, IEEE-assigned
Vendor PN	40–55	168–183	148–163	168–183	16 ASCII
Vendor rev	56–59	184–185	164–165	184–185	4 / 2 / 2 / 2 ASCII
Vendor SN	68–83	196–211	166–181	196–211	16 ASCII
Date code	84–91	212–219	182–189	212–219	8 ASCII
CLEI code	—	page 02h, if byte 129 bit 4	190–199	—	10 ASCII
Vendor specific	96–127 (A0h), A2h user EEPROM 128–247	224–255, page 02h	223–255, custom pages	224–255	free

Byte-level maps: Memory map.

Encoding rules

ASCII only, printable range 20h–7Eh. No NUL (00h), no FFh, no control characters.
Left-justified, padded with spaces (20h) to the full field length. A 10-character part number is followed by six spaces, not six zeros.
Vendor name is the manufacturer's (or brand owner's) name as registered — the string hosts compare, typically case-sensitively.
OUI is the 24-bit IEEE organisationally unique identifier of the company in the name field, written high byte first; 00-00-00 means unspecified. Hosts rarely check it, but a mismatch between OUI and name is an easy fingerprint of a recoded module.
Revision is free-form (often A, 01, 1.0), spaces if none.
Serial number should be unique per vendor; many vendors embed year/week and a running count; some hosts use its structure to recognise their own modules.
Date code is YYMMDD followed by a 2-character vendor lot code (spaces if none): 240315 = 15 March 2024.
CLEI (Common Language Equipment Identifier) is a 10-character telecom asset code, present mostly on modules sold to carriers.

What hosts match on

Host behaviour	What it compares	Typical of
Name + PN lookup	vendor name and part number against a compatibility table	most enterprise switches
PN prefix / family	first characters of the PN	platforms with broad "supported family" lists
Vendor-specific signature	a hash or magic value in the vendor area, computed from SN and other fields	strict OEM locks
SN pattern	structure of the serial number	some OEMs, for warranty and authenticity
OUI	IEEE identifier	rare; some NICs and NOS
Nothing	accepts anything with valid checksums	open switches, most NICs with unsupported-SFP allowed

Which platform does what, and how to respond, is the subject of Vendor lock and Third-party optics.

Common mistakes

Mistake	Symptom on the host
NUL padding instead of spaces	truncated or garbled name, module marked unsupported
Field one byte too long, spilling into the next	corrupted OUI or PN, checksum mismatch
Lower/upper-case differing from the reference	PN not matched by the compatibility table
Non-ASCII bytes (UTF-8, Cyrillic)	question marks or refusal
Date code with letters in the digit positions	display errors; some hosts reject
Vendor block changed, checksums not	module invalid — see Checksums
Name changed, vendor-specific signature left	still unsupported on strict platforms
Identity inconsistent with compliance codes or wavelength	speed and type not supported — see Compliance codes

Vendor-specific areas

The specifications leave the vendor areas undefined on purpose. Manufacturers store calibration backups, production data, configuration for the controller and — on locked modules — authentication data there. Overwriting them blindly can brick a module or break its lock check; copying them from a reference module without the matching serial often fails the check anyway. Treat them as opaque unless you know the vendor's layout (EEPROM recoding).

In CodingBox

The EEPROM editor edits each vendor field as text, pads with spaces to the exact length, refuses non-ASCII input, and recalculates the checksums on write. The code database stores complete identities so a known-good vendor block can be applied in one step.