Devices within LAN not connecting

[dondondon]

I have been wrestling with this problem for several weeks now and obviously need help (your help?). I have a single ASUS3100 router in pretty much the default configuration. Nothing fancy. I have 3 Windows PCs and a couple of Raspberry Pi Pico-W microcontrollers all connected to the router wirelessly. All these devices are able to communicate outwardly to the internet. My problem is that most of the time, several of these devices don't see each other within the LAN. The router shows all devices with excellent signal strength. If I try to ping one PC from another, I am only sometimes successful. Usually: "Destination not found". I've tried ping -t <ip> and I get that same response for at least several minutes. When I use Thonny on a PC and execute micro-python code on a pico (to set up a server or client), I can see that the devices are successful in connecting to the router, but they can't communicate with each other. Ignoring the micro-controllers for now, why can't 1 PC see another PC ? Sometimes they see each other via ping and many times they don't. If I issue "arp -a" from a command window on a PC, the PCs don't all appear many times. Yet, ALL devices are showing up in the client list when I look at it after logging into the router itself So the router knows the devices are all there ! I've toggled AP isolation and UPnP and neither testings have shown improvement. Note that maybe 10% of the time, I can successfully ping 1 PC from another. Learning about arp ( https://www.networkacademy.io/ccna/ethernet/what-is-arp ), it seems that these PCs should be pingable from each other. What am I missing? My goal is to understand the behavior I am seeing, and then to get the micro-controllers to then talk to each other on the LAN.

 

[dondondon]

I have been wrestling with this problem for several weeks now and obviously need help (your help?). I have a single ASUS3100 router in pretty much the default configuration. Nothing fancy. I have 3 Windows PCs and a couple of Raspberry Pi Pico-W microcontrollers all connected to the router wirelessly. All these devices are able to communicate outwardly to the internet. My problem is that most of the time, several of these devices don't see each other within the LAN. The router shows all devices with excellent signal strength. If I try to ping one PC from another, I am only sometimes successful. Usually: "Destination not found". I've tried ping -t <ip> and I get that same response for at least several minutes. When I use Thonny on a PC and execute micro-python code on a pico (to set up a server or client), I can see that the devices are successful in connecting to the router, but they can't communicate with each other. Ignoring the micro-controllers for now, why can't 1 PC see another PC ? Sometimes they see each other via ping and many times they don't. If I issue "arp -a" from a command window on a PC, the PCs don't all appear many times. Yet, ALL devices are showing up in the client list when I look at it after logging into the router itself So the router knows the devices are all there ! I've toggled AP isolation and UPnP and neither testings have shown improvement. Note that maybe 10% of the time, I can successfully ping 1 PC from another. Learning about arp ( https://www.networkacademy.io/ccna/ethernet/what-is-arp ), it seems that these PCs should be pingable from each other. What am I missing? My goal is to understand the behavior I am seeing, and then to get the micro-controllers to then talk to each other on the LAN. PS -- All devices have IPs such as 192.168.1.XXX so they are all on the same "node". Also, each PC is marked as "discoverable" in Windows.

 

[bennor]

Couple of standard troubleshooting suggestions. If it is the Windows PC's that cannot ping or see each other check for the following things on those PC's:
If running a software firewall, anti virus, or security software on the PC, temporarily disable those programs and see if you can ping. Its possible those programs are using a firewall that is blocking access from other PC's.
Check the Network Type or Network Profile Type setting on Windows. Make sure it's configured for Private. That should enable File and Print sharing to be active and allow local network access.
Ensure all local network devices are using the same IP address range (ex: 192.156.1.x) and are all using the same "workgroup" name.

Edit to add: It would likely help others assist in diagnosing your issue if you include the firmware version the router is running. If the router is running Asus-Merlin firmware then list any add-on scripts that are running on the Asus-Merlin firmware.

 

[dondondon]

I didn't do the firewall check yet. All 3 PCs have the private network profile, same "WORKGROUP" name, File/Print sharing enabled, along with network discovery. The firmware is: 3.0.0.4.386_48263 I will attempt turning off the firewall later tonight or tomorrow. Also, all addresses are 192.168.1.xxx where xxx is between 1 and 255. All have same sub-mask 255.255.255.0

 

[dondondon]

Today, I turned the firewalls off and did the pinging between my 3 PCs. Results below:

So with firewalls off, PC3 could ping both PC1 and PC2 and vice versa, but PC1 could only ping PC3. PC2 could ping PC3.
With firewalls back on, PC3 could ping both PC1 and PC2. PC2 could ping PC3. But PC1 could NOT ping PC2 or PC3.

PC1 only has Windows 10 on it (Win 11 won't fit). PC2 and PC3 are up-to-date Windows 11 machines.