May I ask what version of Pluto you are using? On mine I have found that the IP address can be found in 2 different locations when using an SSH connection, I use 0303 so how much it differs between versions I am not sure.
1) is in /www/config.txt This on mine does not show the correct settings in-fact shows 192.168.1.8, mine operates on 192.168.1.32.
2) is in /mnt/jffs2/etc/config.txt
This number 2) is the one that needs to be set on my Pluto for it to work and is the config.txt file that is the original analog device one.
after connecting to the Pluto via SSH terminal
cd /mnt/jffs2/etc
ls this is to list the files and I show: -
config.txt dropbear settings-datv.txt settings.txt strategy.json
cat config.txt to display the contents, if you wish to change the USB ETHERNET address this is where I would do it.
I use nano config.txt and edit the file while is SSH terminal cntrl X and y and y to save the file and exit.
I think as I have done going through all the updates from one version to another I have left over settings in various places, perhaps I need to do a complete start from scratch using 0.32 firmware and the DFU process, but that is for another day.
As an aside to this I have just help another user this evening with a corrupt Pluto so had to go through the DFU process to recover it. It was found that if we jump straight in and install version 0201 firmware that we could not use the Windows method of configuring it as you would a USB drive, the config.txt would not hold, we had to back track and go back to the analog devices 0.32 firmware again, then change the ip address within config.txt, which would then stay put when powered off and back on before installing version 0201.
Sorry this reply is a long one and I hope you did not fall asleep in reading it, hope it helps but make yourself aware of how to recover things with the DFU routine. I have used this 4 or 5 times myself with playing around and messing things up.
Adrian