Networking
The way computers talk to one another.
Every computer on a network has it's own address. IP address -- Internet Protocol
https://www.google.com/search?q=ubuntu+gnome+3+change+IPs
ubuntu gnome 3 change IP - Google Search
https://www.lifewire.com/how-to-configure-networking-in-gnome-4682592
How to Configure Networking in GNOME
There are ip address ranges that are designated for internal (private) networks.
192.168.1.x is a common one.
Documenting
What's a good layout for ip assignments? Example documentation
CSV
Keep your layout in your own csv file. eg.
~/home/network.csv
or
~/notes/home/network/layout-network.csv
for sharing, a spreadsheet is a lot easier. can still track it in version control in the meantime
MD
a text file is also ok whatever is easiest to keep up to date
~/notes/home/network/layout-network.md
SVG
Good for network diagrams
What about keeping the data in an SVG?
Or a web-based SVG interface backed by a database?
Interface Configuration
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.
Ubuntu
On a Raspberry Pi, disable cloud config: To disable cloud-init's network configuration capabilities, write a file /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
network: {config: disabled}
Find the interface in use
ip address
enp0s25
The netplan configuration is located in /etc/netplan
cd /etc/netplan
sudo cp 01-network-manager-all.yaml 01-network-manager-all.yaml.dhcp
Modify the netplan configuration.
sudo vi 01-network-manager-all.yaml
add a section like:
network:
ethernets:
eth0:
dhcp4: no
addresses: [192.168.1.200/24]
gateway4: 192.168.1.1
nameservers:
addresses: [8.8.8.8,4.2.2.2]
To apply the configuration and have changes take effect, run:
sudo netplan apply
Copy SSH keys to the new machine
Remote Connections
Ngrok looks like a cool service that can expose a local service via a remotely accessible address
Following along with:
https://www.endtoend.ai/tutorial/ngrok-ssh-forwarding/
Sign in: https://dashboard.ngrok.com/signup
On the server with the service you want to access,
wget https://bin.equinox.io/c/4VmDzA7iaHb/ngrok-stable-linux-arm64.zip
unzip /path/to/ngrok.zip
chmod +x ngrok
or
sudo snap install ngrok
Start up the forwarding
ngrok tcp 22
Connect to the service from any remote system:
ssh <YOUR_USERNAME>@0.tcp.jp.ngrok.io -p 11111
Open Ports
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
Similar to netstat, but the focus is on processes:
ss -nutlp
lsof -i
via: https://www.thegeekdiary.com/centos-rhel-how-to-find-if-a-network-port-is-open-or-not/
To scan open ports from another (external) machine that's on the same network
nmap [ip of machine to scan]
Common Ports
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
Firewall
Firewalls block external traffic from entering internal networks and hosts.
iptables
iptables -xvn -L
DNS
To resolve a name associated with an IP address, try nslookup:
nslookup 129.79.5.100
To go the other way and find the IP of a configured domain name, dig can help:
dig +short unix.stackexchange.com
Don't forget! You can always add the host & ip to your /etc/hosts file and then it will resolve and you can test the service before the dns entries propagate! 😃
Traceroute
sudo apt install inetutils-traceroute
Traffic Analysis
Wireshark
To see what is happening on a network, use wireshark
https://www.wireshark.org/ Wireshark · Go Deep.
sudo apt install wireshark
https://jvns.ca/blog/2018/06/19/what-i-use-wireshark-for/
To see statistics on TCP connection duration:
'Statistics' -> 'Conversations'
Other tools
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.