I have, what I believe to be, a very strange networking problem and haven't found any resolution. The short version is this: I have several machines on a home network (connected to each other via WiFi) that each have no issues browsing the Internet, and frequently have no issues talking to each other (e.g. via SSH/PING). However, almost as frequently, one or more machines cannot reach other machines, giving errors like 'ssh: connect to host 192.168.0.24 port 22: No route to host'. When this happens, the machine that is failing to connect can access the Internet fine, and can ping the router (192.168.0.1) fine. It just cannot connect to other machines on the local area network. If I put the machine in a "ping loop", eventually, it will be able to connect (or rather get an ICMP response). At that point, if I interrupt the ping loop, I can ssh to the destination machine fine.
I frequently use the following trick, which also works: I'll use the example of one machine (MacBook Pro) with IP address 192.168.0.105, trying to connect to a Thinkpad running Ubuntu 20.04 LTS. I try to "ssh" and it fails (as above). Then, I ssh from 192.168.0.105 to a virtual host on the internet that has an OpenVPN tunnel to/from 192.168.0.24. From the virtual host, I SSH to the 192.168.0.24 machine (using, of course, a tun IP address of the VPN). Then, from 192.168.0.24, I ssh to 192.168.0.105, and once connected (or even once prompted for a password), I disconnect all sessions. At this point, I can now connect from 192.168.0.105 to 192.168.0.24 successfully.
I have several machines (Macs, Linux) on my home network. The "issue" I described above is not limited to that pair of computers. I have the same issue when (from, say a Mac at 192.168.0.20), I want to print a document. I have an HP printer connected to the local network (via WiFi) and macOS, in this case, says it cannot connect to the printer (192.168.0.23). The document is queued and sometime later (sometimes as much as 30 minutes later), it prints, once macOS has been able to connect to the printer.
So, in short, I have an intermittent network connection issue. I can "hack" it to connect (as described above), but this is highly inconvenient, and only works between the few machines (including Raspberry Pis) that have an OpenVPN tunnel to my virtual host.
Now, a few additional details since I'm sure someone will ask: I have an Internet connection to the house via cable. It comes into a Cable Modem. That cable model is connect to a TP-Link (wired) router. That router has the IP address 192.168.0.1 (remember I said that all machines have NO issues PINGing the router -- even when they can't connect to other machines on the local network). Plugged into the (wired) router, I have an ASUS WiFI router. It is that WIFI router that is servicing all the hosts on the 192.168.0.0/24 subnet. I actually have a second Wifi router (TP-Link, that is connected (via ethernet cable) to the wired router. It hands out IP addresses on the 192.168.1.0/24 subnet. I don't think it is really relevant to my issue, which is between hosts on the 192.168.0.0/24 subnet.
Can anyone suggest any things that might be causing this? Any things I can try to narrow down the problem? I'm currently suspecting that my ASUS Wifi router is "having issues", but I don't know that for sure. I have no idea why just "waiting a while" allows me to connect between hosts on the 192.168.0.0/24 subnet. Thoughts?
I frequently use the following trick, which also works: I'll use the example of one machine (MacBook Pro) with IP address 192.168.0.105, trying to connect to a Thinkpad running Ubuntu 20.04 LTS. I try to "ssh" and it fails (as above). Then, I ssh from 192.168.0.105 to a virtual host on the internet that has an OpenVPN tunnel to/from 192.168.0.24. From the virtual host, I SSH to the 192.168.0.24 machine (using, of course, a tun IP address of the VPN). Then, from 192.168.0.24, I ssh to 192.168.0.105, and once connected (or even once prompted for a password), I disconnect all sessions. At this point, I can now connect from 192.168.0.105 to 192.168.0.24 successfully.
I have several machines (Macs, Linux) on my home network. The "issue" I described above is not limited to that pair of computers. I have the same issue when (from, say a Mac at 192.168.0.20), I want to print a document. I have an HP printer connected to the local network (via WiFi) and macOS, in this case, says it cannot connect to the printer (192.168.0.23). The document is queued and sometime later (sometimes as much as 30 minutes later), it prints, once macOS has been able to connect to the printer.
So, in short, I have an intermittent network connection issue. I can "hack" it to connect (as described above), but this is highly inconvenient, and only works between the few machines (including Raspberry Pis) that have an OpenVPN tunnel to my virtual host.
Now, a few additional details since I'm sure someone will ask: I have an Internet connection to the house via cable. It comes into a Cable Modem. That cable model is connect to a TP-Link (wired) router. That router has the IP address 192.168.0.1 (remember I said that all machines have NO issues PINGing the router -- even when they can't connect to other machines on the local network). Plugged into the (wired) router, I have an ASUS WiFI router. It is that WIFI router that is servicing all the hosts on the 192.168.0.0/24 subnet. I actually have a second Wifi router (TP-Link, that is connected (via ethernet cable) to the wired router. It hands out IP addresses on the 192.168.1.0/24 subnet. I don't think it is really relevant to my issue, which is between hosts on the 192.168.0.0/24 subnet.
Can anyone suggest any things that might be causing this? Any things I can try to narrow down the problem? I'm currently suspecting that my ASUS Wifi router is "having issues", but I don't know that for sure. I have no idea why just "waiting a while" allows me to connect between hosts on the 192.168.0.0/24 subnet. Thoughts?