The way computers talk to one another.
Every computer on a network has it's own address. IP address -- Internet Protocol
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There are ip address ranges that are designated for internal (private) networks.
192.168.1.x is a common one.
On a linux machine you can install
netstat to see what ports are currently open:
sudo apt install net-tools netstat -pan | egrep " LISTEN " netstat -tulnp
t – Show TCP u – Show UDP l – Show only listening processes (netstat can show both listening and all established connections, i.e. as a client too) n – Do not resolve network IP address names or port numbers p – Show the process name that is listening on the port
netstat, but the focus is on processes:
ss -nutlp lsof -i
To scan open ports from another (external) machine that's on the same network
nmap [ip of machine to scan]
By convention, common services utilize specific ports to publish and connect to the service. Some examples include:
SSH 22 DNS servers 53 tcp potential trojan (probably dns) ipps 631 Internet Printing Protocol over HTTPS
Firewalls block external traffic from entering internal networks and hosts.
iptables -xvn -L
To resolve a name associated with an IP address, try nslookup:
sudo apt install inetutils-traceroute
To see what is happening on a network, use wireshark
https://www.wireshark.org/ Wireshark · Go Deep.
sudo apt install wireshark
To see statistics on TCP connection duration:
'Statistics' -> 'Conversations'
https://www.reddit.com/r/networking/comments/78mtfj/looking_for_an_open_source_network_traffic/ Looking for an open source Network Traffic Analyzer : networking
https://github.com/robcowart/elastiflow GitHub - robcowart/elastiflow: Network flow analytics (Netflow, sFlow and IPFIX) with the Elastic Stack http://pmacct.net/ pmacct project: IP accounting iconoclasm https://gitlab.com/thart/flowanalyzer Manito Networks / flowanalyzer · GitLab https://www.ntop.org/ ntop – High Performance Network Monitoring Solutions based on Open Source and Commodity Hardware.
Often it's pretty straightforward to use a GUI. If you want to configure an interface via a CLI, it's necessary to know where the OS stores the configuration settings. This varies from OS to OS.
Find the interface in use
The netplan configuration is located in /etc/netplan
cd /etc/netplan sudo cp 01-network-manager-all.yaml 01-network-manager-all.yaml.bak
Modify the netplan configuration.
sudo vi 01-network-manager-all.yaml
add a section like:
ethernets: eno2: dhcp4: no addresses: [192.168.1.200/24] gateway4: 192.168.1.1 nameservers: addresses: [184.108.40.206,220.127.116.11]
sudo netplan apply
to apply the configuration and changes to affect.