Re: Sometimes it can be dhcp
Printers? DHCP? How about we set the wayback machine for early 90s, with some lab gear. The devices did not use DHCP, or bootp, but RARP. Having gotten an IP address, they fetched various config data via TFTP. Worked fine (for small enough values of "fine").
Then it didn't.
One day we started getting complaints that the boxen could not be accessed from Windows (NT3.1?). Worked fine from SunOS, SYSV on 386, even VMS Vaxen. Huh?
Apparently, someone had brought in a "network printer adapter", so they could use their Centronics-cabled printer over ethernet. This box had the charming feature of, if it saw an RARP reply, deciding that it was the intended recipient, and re-assign its IP to that in the reply (which it had not solicited).
When a user initiated a connection, and it had not already, it would ARP for the desired IP address. The actual box, _and_ the "mini network print server" would both respond. Which MAC address should it use?
Apparently, most OSes would take the first ARP reply, while Windows would take the most recent. Since the computers were typically in the same lab, if not on the same bench, the gear was on the same ethernet segment and would be seen first. The printer adapter was on a different segment, so would reply later. Windows, and only Windows, would accept the second, unsolicited, update. So the first packets actually intended for the lab gear were instead sent to the printer adapter, which for some reason was not listening on any of the intended ports.
Sorry about the verbosity. trust me, the actual diagnosis took longer than typing (or reading) this.
Suffice to say that this pioneer of BYODADTI (Bring your own device and don't tell IT) a department head, of course, was informed of what his brilliant actions had wrought.
Then an actual policy about such unsolicited upgrades was written. (and read? don't be silly)