Use SNMP and Access point wifi - wifi

I am not an expert of the network domain.
Today I have a network with a connection to the Internet. Some computers use an ethernet connection, others use the WIFI.
I wish to monitor the network because we have a slow connection.
I plan to add a switch with SNMP in front of my modem.
If I connect an access point wifi on the switch, would I be able to differentiate the different computers connected in wifi ?
Thank you,

Any network equipment that has the BRIDGE-MIB RFC 1493 implemented will let you check which port is doing what on your network. You would want a switch/router that is also an access point, or if separate equipment, then the access point needs the BRIDGE-MIB.

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Internet connection problem from different network for NodeMCU ESP8266 which I am using for IOT home automation

Would anyone like to help me with this problem please?
how to connect/control Nodemcu esp8266 wi-fi module from different network for control iot devices from outside of any home/ house?
Internet connection problem from different network for NodeMCU ESP8266 which I am using for IOT home automation.
Actually, in case of an class project, I have used some code (also coppied some code and took help from some website) from internet and also used Blynk for controll my ESP8266.
But not i want to make a personal app by which app I can control my devices outside from my home.
I have already connected with my WI-FI router with my home network!!
It worked well,
But i don't know how to do the same thing from different netwrok.
If possible I think anyone can help me....
Thank you.
To everyone.
This has been answered in greater detail on both the Arduino and Internet of Things StackExchange sites. In summary:
For safety, it is difficult to start a connection to a device on another local network. Devices on WiFi networks are protected from the Internet by a firewall, which is normally configured to return responses to requests sent by the devices, but block all unsolicited messages. Even if the firewall allows an incoming connection on a given port, "port forwarding" or other custom configurations are needed for unexpected messages to reach one of the multiple devices on the network (the devices usually share the same public IP address of the network and external systems' messages cannot reach the right local address without forwarding by the router).
Any device exposed to unsolicited requests like this is at risk of being attacked and can pose a risk to other systems on the network. It is thus safer to leave the firewall the same and instead make the device subscribe to an external webserver, which acts as a mailbox for incoming messages. Then, you can send requests to the server from anything with an internet connection, and the server will store them and relay them to the ESP8266 whenever the ESP asks. MQTT protocol using a server-side broker program like Mosquitto and a client like PubSubClient on your ESP8266 could work for this sort of publish-subscribe model, and MQTT tutorials and explanations are available both on both tool sites and Stack sites.
You can use Arduino IDE to program ESP8266 device.
https://randomnerdtutorials.com/how-to-install-esp8266-board-arduino-ide/
After installing ESP8266 in Arduino IDE. You need to connect ESP8266 with WiFi router(which have internet connected). Once your device is connected with a WiFi router. you can MQTT protocol to communicate with the server. You can use the following library in Arduino to implement MQTT client in ESP8266. ESP8266 is used to send and receive data from a different network. ESP8266 is subscribed to a particular topic. You can publish data to that topic from different MQTT client.
https://github.com/Imroy/pubsubclient
Use the Following link to get more familiar with MQTT protocol
https://www.hivemq.com/blog/mqtt-essentials-part-1-introducing-mqtt
You can use MQTTfx desktop application to send and receive data from NodeMcu(ESP8266).
MQTT basic diagram for understanding

Usb internet key & Raspberry: disable internet connection, used only for sms

I would like to use a USB internet Key Huawei E3531i for send and receive SMS.
I'm working on it, I can send but I have some issue receiving but this is not the topic of this thread.
When I plug the USB stick the Raspberry (connected to wireless lan) doesn't have access to internet any more. Most probably because somehow the internet key is considered as preferred connection but I don't have idea how to change this.
The best for me would be that the USB stick is not used at all for internet connection, even the wireless lan is not available.
How to configure this?
Thanks
Andrea
SOLVED!
Editing the file: /etc/dhcpcd.conf
Adding the metric for each interface. In this way I can drive the priority of routing for internet connection:
interface wlan0
metric 200
interface eth1
metric 300
The smaller number has higher priority.
Now I'm able to reach the internet key with his static ip address but also connecting to internet because the default interface is the wifi.
Bye
Andrea

Creating a Wi-Fi local network with no Internet access in RaspberryPi3

I need to create a wireless network with no Internet access with a Pi, because I need to communicate to it with an Android smartphone and a laptop, but being the RPi the highest step in the network hierarchy.
I've found -and tried- that I can do an adhoc network, but I am unable to connect to it with the smartphone. The other alternative is creating a Wi-Fi hotspot, with no NAT, but I don't really have a deep knowledge on networks so I'm really lost in which IP adresses I have to set.
I've followed this tutorial, and found it really useful. Could anyone tell me what should I modify from it to make it only local -apart from not doing the NAT?
The Rapsberry Pi 3 has built in Wi-Fi that can serve as an access point. Based on my experience, with the Pi acting as an access point, you should be able to connect to any device, be it Android or not.
The Pi will act as access point and serve as a DHCP daemon, assigning and handling IP addresses to any devices that connect to it. This will be a standalone network and will not be able to share an Internet connection unless you bridge it. Follow this tutorial up until the Internet sharing part:
https://www.raspberrypi.org/documentation/configuration/wireless/access-point.md
Also, it would be better to ask this in the Raspberry Pi stack exchange.

Can wifi access be given to specific applications?

Which is the best appplication way to give access to free wifi to particular applications only (say whataspp)?
Yes, its possible through a (logical)firewall between the wifi network and the gateway.
Whatsappp-packets can be detected by tcp port number and destination ip.
there are some good wifi/gateway/firewall combi-devices, e.g all openWRT and routerOS devices

Can't see another computer in WiFi

I am trying to do a little experiment and I'm getting pretty odd results that I can't explain. I came to my University with my friend, we both brought our laptops and we connected to the same WiFi. But from some reason, our computers couldn't communicate with each other. For example, I couldn't ping him, and I when I did an ARP Scan to find all the hosts on the LAN I didn't find him. He did the same. He couldn't ping me and he didn't find my laptop when he did an ARP scan. Yet, there were many other devices on the LAN that both of us could ping and that we both found in our ARP scan. The University may be big, but we sat just next to each other.
I know that the WiFi on the university may be complex, but yet I have no explanations of what is happening. We sit next to each other, connect to the same WiFi(same Access Point MAC), we both see many same devices in our LAN, yet we can't see each other. Anyone has any idea of what may be happening? Why can't we see/ping each other while we are on the same LAN?
Thanks! :)
The wireless access point probably has a security setting of "Wireless Isolation Within SSID" turned on. This function does exactly what you describe. It allows all authenticated users to see machines on the LAN, but not other wireless machines on the same access point.
Reconfigure your router and make some settings like this
LAN DHCP=Enable
Wireless Authentication type=WPA-PSK/WPA2-PSK
Encryption=AES
After this setting delete all Wireless network of router listed in your PC. And than connect, It will works. you can ping your both PC together.
Because you are connected to an infrastructure mode access point (99% of APs), in order to send packets to another device your laptop sends the packet to the AP (to the distribution system), and then the AP sends the packet to your friend (from the distribution system). You cannot connect 'directly' to your friend.
The AP can direct whether or not wireless clients can see each other - depending on the manufacturer this can be implemented in many different ways. You could talk to your system administrator about why/how this policy works.

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