Interface Status
ip link show
- Shows all network interfaces
- Up/down status and MAC addresses
ip addr show [interface]
- Display IP addresses per interface
- Shows subnet masks and scope
ifconfig [interface]
- Legacy interface configuration tool
- Shows stats: RX/TX packets, errors
Connectivity Testing
ping -c 4 [host]
- Send 4 ICMP packets to target
- Tests basic connectivity
traceroute [destination]
- Shows path packets take to dest
- Identifies routing issues
mtr [host]
- Combines ping and traceroute
- Real-time network diagnostics
DNS Resolution
nslookup [domain]
- Query DNS for domain records
- Shows configured DNS servers
dig [domain]
- Advanced DNS lookup tool
- More detailed output than nslookup
systemd-resolve --status
- Shows DNS resolver configuration
- Current DNS servers in use
Network Services
ss -tulpn
- Show listening ports and services
- TCP/UDP with process names
netstat -rn
- Display routing table
- Shows gateway and routes
systemctl status networking
- Check network service status
- Shows if networking is active
Configuration Files
cat /etc/network/interfaces
- Static network configuration
- Interface definitions
cat /etc/resolv.conf
- DNS resolver configuration
- Current nameservers
Example Troubleshooting
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