Hi, I’m MaskerTim.
and I attach a diagram about my network architecture and what problem I have.
Under the premise on my network setting:
I don’t know why fault it is?
Well i wouldn’t pass intranet through a wifi router’s WAN port, but first impulse is that the firewall inside the router is blocking incoming signals because thats what routers do for signals coming from WAN - reject unless port mapped.
Oh, that’s one possible problem of port mapping. Thanks, you give me one way to try it.
Ping is not a good way to test network connectivity, all sorts of stuff won’t respond to pings.
the reason that ping don’t respond is the firewall block the message, isn’t it? Or, Is it still other reasons that make ping don’t respond?
If you ping Device A from Device B, do you get a response?
What droopsnoot is rightly pointing out is that devices can easily not respond to pings. Or any other signal, if their internal systems tell it not to listen to traffic on ICMP ports.
I just vaguely recall being told that not getting a response to a ping doesn’t actually mean that there’s anything sinister going on, and that there are other ways to test network connectivity that are often better. “Security reasons” meant that things started to be less likely to respond to general probes, only to connections to specific ports. We’d often get situations in the field where the installer would phone in having set everything up, but be unable to ping the device.
Yes, when I ping Device A to B (Both all use raspberry pi), I can get response. And I can send from Device A to Server A (that’s not in the same subset network). But I can’t send reversely, Server A can’t get any response from Device A.
Then I go back to my original position, the wireless router’s your problem point.
Oh, I understand what you talk. The device I use is a Raspberry Pi. You mean the port in the device may be not open to listen. So it is unable to response or accept the ping packet message by their port in that device. That’s also a possible problem which may happen. I will try these way to solve this problem. If you have other thinking you guess, please tell me anything you think. Thanks. 
Maybe it is, I will try these ways in a lab of my group for a few days later. If you have any thinking what problem it is, please communicate with me. Thanks you.
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