How to find device in an unknown subnet

[DominikHoffmann]

My UPS is connected to my Ethernet network. However, I do not know, what IP address it was configured with (I purchased it used). What’s the best way to try to find the IP address, when I have my Mac connected to the UPS with an Ethernet cable directly? What software should I use?

 

[iStorm]

Is there no way to reset it to factory defaults so that you can set it up from scratch? There's typically a reset button somewhere.

 

[DominikHoffmann]

There is, but the documentation is somewhat murky on this. As far as official documentation is concerned, it will only reset the user ID and password to apc/apc but retain the IP settings. In order to change those, one has to set up a serial connection to the UPS. The problem with that is that it uses a custom-wired DB-9 cable, which was not supplied with the UPS I purchased.

 

[satcomer]

There is, but the documentation is somewhat murky on this. As far as official documentation is concerned, it will only reset the user ID and password to apc/apc but retain the IP settings. In order to change those, one has to set up a serial connection to the UPS. The problem with that is that it uses a custom-wired DB-9 cable, which was not supplied with the UPS I purchased.

Maybe with some Like this too configure it!

 

[DominikHoffmann]

Maybe with some Like this too configure it!

I’d still need a DB-9 breakout connector to match the standard RS-232 wiring on the end of what you are suggesting to what the UPS expects. For some reason, APC decided on proprietary pin-outs. While those have been sufficiently well reverse-engineered, they are unique. They are unique even between different APC models. It’s hard to think why this would have been anything but an anti-competitive feature.

 

[mikeboss]

by creating an entry in the ARP table of your Mac it should be possible to connect to the UPS no matter what IP address it has configured.

arp -s [unused IP in the same subnet] [MAC address of UPS]
now you should be able to connect to the UPS via [unused IP in the same subnet]

the ARP table will be reset when Mac is rebooted.

 

[hobowankenobi]

A handy tool to have is Angry IP Scanner. I have not tried scanning for a single directly connected device, but worth a shot.

 

[BorderingOn]

You’re probably going to need the serial cable, but wireshark should reveal the IP address, or simply tcpdump.

 

[mikeboss]

A handy tool to have is Angry IP Scanner. I have not tried scanning for a single directly connected device, but worth a shot.

and do what? scan all 17'891'328 IP addresses in the three private ranges?

 

[hobowankenobi]

I simply said it was a handy tool to have. Not everybody lives in ARP tables. I also pointed out that I have no experience trying to detect a single device plugged directly into a computer.

it does have some detection abilities. It would take 5 minutes to try, tops. What's the harm?

 

[mikeboss]

I simply said it was a handy tool to have. Not everybody lives in ARP tables. I also pointed out that I have no experience trying to detect a single device plugged directly into a computer.

it does have some detection abilities. It would take 5 minutes to try, tops. What's the harm?

I do own a hammer. this often is a handy tool to have... what I mean to say: an IP scanner simply isn't the right tool in this scenario. it won't help at all unless both are in the same subnet, which would be an extremely unlikely coincidence (like winning the lottery). and the ARP table is no magic stuff ;-)