Port & Network Management

Port management, network configuration, and connectivity commands for CentOS/RHEL

Port Management Commands

Port checking, monitoring, and management commands

# Check if port is open
netstat -tulpn | grep :80

# Check listening ports
ss -tulpn | grep LISTEN

# Check specific port
nmap -p 80 localhost

# Check port with telnet
telnet localhost 80

# Check port with nc (netcat)
nc -zv localhost 80

# Show all open ports
netstat -tulpn

# Show ports by process
lsof -i :80

# Check port range
nmap -p 1-1000 localhost

# Check UDP ports
netstat -ulpn

# Check port with timeout
timeout 5 telnet localhost 80

Individual commands:

netstat -tulpn | grep :80

ss -tulpn | grep LISTEN

nmap -p 80 localhost

telnet localhost 80

nc -zv localhost 80

netstat -tulpn

lsof -i :80

nmap -p 1-1000 localhost

netstat -ulpn

timeout 5 telnet localhost 80

Network Configuration

Network interface configuration and management

# Show network interfaces
ip addr show

# Show routing table
ip route show

# Show network statistics
ip -s link show

# Configure IP address
ip addr add 192.168.1.100/24 dev eth0

# Bring interface up/down
ip link set eth0 up
ip link set eth0 down

# Show ARP table
ip neigh show

# Flush ARP table
ip neigh flush all

# Show network connections
ss -tulpn

# Show network statistics
cat /proc/net/dev

# Show network interface details
ethtool eth0

Individual commands:

ip addr show

ip route show

ip -s link show

ip addr add 192.168.1.100/24 dev eth0

ip link set eth0 up

ip link set eth0 down

ip neigh show

ip neigh flush all

ss -tulpn

cat /proc/net/dev

ethtool eth0

Firewall Commands (firewalld)

Firewall configuration and management with firewalld

# Check firewall status
systemctl status firewalld

# Start/stop firewall
systemctl start firewalld
systemctl stop firewalld

# Enable/disable firewall
systemctl enable firewalld
systemctl disable firewalld

# List firewall zones
firewall-cmd --get-zones

# List active zones
firewall-cmd --get-active-zones

# Add port to firewall
firewall-cmd --permanent --add-port=80/tcp
firewall-cmd --reload

# Remove port from firewall
firewall-cmd --permanent --remove-port=80/tcp
firewall-cmd --reload

# List open ports
firewall-cmd --list-ports

# Add service to firewall
firewall-cmd --permanent --add-service=http
firewall-cmd --reload

# List services
firewall-cmd --list-services

# Block IP address
firewall-cmd --permanent --add-rich-rule="rule family='ipv4' source address='192.168.1.100' reject"
firewall-cmd --reload

Individual commands:

systemctl status firewalld

systemctl start firewalld

systemctl stop firewalld

systemctl enable firewalld

systemctl disable firewalld

firewall-cmd --get-zones

firewall-cmd --get-active-zones

firewall-cmd --permanent --add-port=80/tcp

firewall-cmd --reload

firewall-cmd --permanent --remove-port=80/tcp

firewall-cmd --reload

firewall-cmd --list-ports

firewall-cmd --permanent --add-service=http

firewall-cmd --reload

firewall-cmd --list-services

firewall-cmd --permanent --add-rich-rule="rule family='ipv4' source address='192.168.1.100' reject"

firewall-cmd --reload