Networking Tips Tricks and Solutions

All of these details are assuming linux/ubuntu.

nmcli: Managing Connections

Awesome tool to be able to see and manage wifi networks.

To list available wifi networks, and their strengths:

nmcli dev wifi

To connect to a specific network:

nmcli device wifi connect "$SSID" password "$PASSWORD"
nmcli --ask device wifi connect "$SSID"

The second one will prompt you for a password if necessary.

To get details on the networking devices on your computer:

nmcli -p -f general,wifi-properties device show

To install nmcli:

sudo apt-get update && sudo apt-get install network-manager

To enable it without rebooting:

systemctl start NetworkManager.service

or to enable on boot:

systemctl enable NetworkManager.service

Reference: https://man.archlinux.org/man/nmcli-examples.7.en

ip, ifconfig, iwconfig: Details on current network

To get the computers ip or mac addresses, run any of

ip a
ifconfig # all network interfaces
iwconfig # specifically for wireless

iperf3: Bandwidth Measurement

iperf3 is a tool to measure wifi strength and bandwidth.

To install:

sudo apt-get install iperf3

To test the connection speed between two computers, you will start the first computer as a server:

iperf3 -s -f m

Flags:

  • -s enables the server mode
  • -f K sets the format to KBytes. You can also use k, m, g, K, M, G for kbits, mbits, gbits, kbytes, mbytes, gbytes respectively.
  • -p 3000 sets the port to 3000 (default is 5201)

Then on the client (i.e., the machine where the actual benchmarking takes place), run

iperf3 -c [server_hostname/ip_address] -f m

Flags:

  • -c $SERVER_IP enables client mode, and specifies the server’s ip address.
  • -f is as before
  • -w 500K will set a TCP window size
  • -R will test it in reverse mode
  • -d will test it both directions simultaeneously
  • --udp will test UDP instead of TCP

Reference: https://www.tecmint.com/test-network-throughput-in-linux/

ping: Measuring Latency

Run

ping [hostname/ip_address]

or specify whichever ip address you want to measure the latency of. Pay attention to the summary outputs at the end to see a spread. Flags:

  • -i [interval] the interval in seconds at which you want to run ping. Important to set to a small number like 0.2 to avoid network cards intermittantly going to sleep and artificially resulting in a large ping value.
  • -s [size] to specify the size (in bytes) of each packet
  • -f to test it in flood mode. Might need to run in sudo mode, and the results are printed when you hit ctrl-c

nmap: scan the local network for other devices

Assuming you are on a local network with ip address 192.168.1.144 you can scan others by running

sudo nmap -sn 192.168.1.*

which will search for all computers with ip addresses of the form 192.168.1.*

Reference: https://phoenixnap.com/kb/how-to-install-use-nmap-scanning-linux