Some devices on LAN can't ping other devices
I have a Ubee cable modem (DOCSIS 3.0) which also serves as a wired/wireless router and DHCP server. I have devices which are on the LAN and receiving addresses from the Ubee that I can't ping from other devices also on the LAN.
Example:
- Computer A (static IP 192.168.0.50 wired connection)
- Computer B (DHCP IP 192.168.0.83 wireless connection)
- Computer C (static IP 192.168.0.203 wireless connection)
- Ubee (static IP 192.168.0.1)
Results:
- Computer A can ping Ubee and Computer C (Can't ping B)
- Computer C Can ping Computers A and B and Ubee
- Ubee can ping B and C, but not A which is wired to the Ubee and shows up on the client list
(Computer B is a microcontroller and is working fine with MQTT)
Hope I have explained this well enough. It's driving me crazy. Is it something about the Ubee, something dumb I'm doing? Thanks for any help. Bob
Solution 1:
The most likely explanation is simply different kinds of ping and firewalls. Pinging can be done multiple ways, and it is entirely possible firewalls are blocking some types of ping but not others.
A good partial solution could be to examine the ARP tables of each device to see if it knows it's neighbours (after attempting to communicate with them). Because they are all directly connected this should work even where ping doesn't.
It is much less likely, but conceivable that the Ubee is faulty or unable to track the connections and is causing intermittent issues.