Network¶
iproute2¶
iproute2 is the Linux networking toolkit that replaced net-tools (ifconfig, route, arp etc.).
iproute2 is a collection of command-line utilities for managing and monitoring various aspects of networking in the Linux kernel. Common iproute2 utilities:
ip: The primary command for most networking tasks like configuring interfaces, assigning IP addresses, and managing routes.
iw: Manages wireless network interfaces.
ss: Similar to netstat but offers more detailed information on network connections.
tc: Used for traffic control and shaping network traffic.
bridge: Manages bridge networking devices.
Note that iproute2 is more focused on network configuration and management. For DNS-specific tasks, tools like dig, nslookup, or host are more appropriate.
find a free TCP port¶
-l: listening ports only\ -t: TCP ports only\ -n: See port numbers, instead of port names like "http" or "epmap"check what uses a port¶
nslookup¶
NSLOOKUP stands for "Name Server Lookup," used to query the Domain Name System (DNS) to obtain information about domain names, IP addresses, and other DNS records.
nslookup www.example.com will return the domain name and ip address.
dig¶
used to find the domain name of provided ip address
check network connection in docker pod without curl, ping etc¶
can only work under bash
host=1.2.3.4
port=10
echo >/dev/tcp/${host}/${port}
(echo >/dev/tcp/${host}/${port}) &>/dev/null && echo "open" || echo "closed"
connection refused¶
https://stackoverflow.com/questions/2333400/what-can-be-the-reasons-of-connection-refused-errors
reasons:
The port is not open on the destination machine.
The port is open on the destination machine, but its backlog of pending connections is full.
A firewall between the client and server is blocking access (also check local firewalls).
After checking for firewalls and that the port is open, use telnet to connect to the ip/port to test connectivity. This removes any potential issues from your application.