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Nmap

Here’s how to list all the devices on your network using nmap.

nmap -sn 192.168.0.0/24

If nmap is not installed, install it.

yum install nmap
apt install nmap

Netstat

Netstat is a utility for gathering network statistics. It comes preinstalled on most systems.

If missing, here’s how to install.

# Redhat, CentOS
yum install net-tools
# Debian, Ubuntu, Mint
apt install net-tools
# SLES, SUSE
zypper install net-tools

Here are some common and useful commands.

# show version
netstat -v
# show routing table
netstat -nr
# show network interface statistics
netstat -ai
# show network connections
netstat -ant
# show network services
netstat -pnltu

GCP ILB Issue Targets Not Healthy

I ran into an issue with Google Compute Engine TCP internal load balancer. The targets are unhealthy although all configs were correct installed. At one time the targets were working, but somehow they became unhealthy. In the end, 3 things needed to be checked.

  1. Make sure GCP’s guest environment is installed.
  2. Add the internal load balancer VIP address to the network properties.
  3. Add route via cmd. “route ADD VIP MASK 255.255.255.255”

You will need to change the server’s IP from DHCP to static to add ILB VIP.