I have an old Pi1 and a Pi4, both running Buster. (Please don't ask why.)
One of the daily tasks of the 4 is to use scp to copy a bunch of JPEG images from the 1, assemble those into a time-lapse video and upload the video to a web host.
This worked fine for several years. I was away from home a week or so ago when it suddenly stopped working.
It took me many days to figure out why, I found out by trying to run the scp command from the command line of the 4. It failed with a "no route to host" error. Both machine were online using the same SSID. I could SSH into both machines from an old iMac and a more recent MacBook Air. But I couldn't log on to the 1 from the 4. Nor could I ping the 1 from the 4.
That didn't make sense until I looked at the router configuration and saw that the 1 was connected to the 2.4Ghz network while the 4 was connected to the 5 Ghz network. I'm sure that the 1 has always been on 2.4 Ghz because that's all the hardware supports. I'm also sure that the 4 has been on the 2.4Ghz network for at least a few years because the daily scp copy between the machines has never failed.
I've now set the router up so that the 4 will always connect to 2.4Ghz. So, problem solved.
But, the mystery persists. What could have caused the 4 to suddenly switch from 2.4 to 5?
One more thing and perhaps not appropriate for this forum. Both Macs, which are always on 5Ghz, can connect to the 2.4 Ghz machines. Is this because of the wireless hardware the Mac uses or some sort of network software magic?
One of the daily tasks of the 4 is to use scp to copy a bunch of JPEG images from the 1, assemble those into a time-lapse video and upload the video to a web host.
This worked fine for several years. I was away from home a week or so ago when it suddenly stopped working.
It took me many days to figure out why, I found out by trying to run the scp command from the command line of the 4. It failed with a "no route to host" error. Both machine were online using the same SSID. I could SSH into both machines from an old iMac and a more recent MacBook Air. But I couldn't log on to the 1 from the 4. Nor could I ping the 1 from the 4.
That didn't make sense until I looked at the router configuration and saw that the 1 was connected to the 2.4Ghz network while the 4 was connected to the 5 Ghz network. I'm sure that the 1 has always been on 2.4 Ghz because that's all the hardware supports. I'm also sure that the 4 has been on the 2.4Ghz network for at least a few years because the daily scp copy between the machines has never failed.
I've now set the router up so that the 4 will always connect to 2.4Ghz. So, problem solved.
But, the mystery persists. What could have caused the 4 to suddenly switch from 2.4 to 5?
One more thing and perhaps not appropriate for this forum. Both Macs, which are always on 5Ghz, can connect to the 2.4 Ghz machines. Is this because of the wireless hardware the Mac uses or some sort of network software magic?
Statistics: Posted by Ratsima — Sat Jun 14, 2025 3:42 am