00:05:21
Operated by Schneider Electric, FR (4 of 6 rows, HQ area); US (2 of 6 rows — Leesport, PA and Foxboro, MA).
About this prefix.
00:05:21 is registered to Schneider Electric, FR (4 of 6 rows, HQ area); US (2 of 6 rows — Leesport, PA and Foxboro, MA). That page carries the full record: every prefix the organisation holds, its registered address, and the research behind the entry.
00:05:21 is an OUI: the first three octets of a MAC address. Every address beginning with these octets was issued from this block. The remaining three octets are assigned by the block holder to individual network interfaces, so one 24-bit block spans 16,777,216 addresses.
The IEEE Registration Authority is the source of record for these assignments. A 24-bit block can belong to one organisation outright, or be divided into smaller MA-M and MA-S ranges held by several unrelated registrants.
To identify the holder of a specific address, run the full MAC through the MAC address lookup. The vendor directory lists the organisations with a researched profile on this site.