#!/bin/bash # # network_diagnostics.sh # # This script is designed to collect as much information as possible about the # network connection on a Debian Bullseye machine that uses dynamic IP addresses via DHCP. # # Note: Some commands may require root privileges. # # Usage: # chmod +x network_diagnostics.sh # sudo ./network_diagnostics.sh # # Feel free to modify or expand this script for your needs. # # ----------------------------------------------------------------------------- # Helper function to check if a command exists and print a header function section_header() { echo "========================================" echo "$1" echo "========================================" } # ----------------------------------------------------------------------------- section_header "NETWORK DIAGNOSTICS REPORT" echo "Report generated on: $(date)" echo "" # 1. Basic System Information echo ">>> SYSTEM INFORMATION" echo "Hostname: $(hostname)" echo "Kernel info: $(uname -a)" if command -v lsb_release >/dev/null 2>&1; then echo "Distribution Info:" lsb_release -a 2>/dev/null else echo "/etc/issue:" cat /etc/issue fi echo "" # 2. Network Interfaces section_header "NETWORK INTERFACES" echo "Using 'ip addr show':" ip addr show echo "" if command -v ifconfig >/dev/null 2>&1; then echo "Using 'ifconfig -a':" ifconfig -a else echo "ifconfig command not found (install net-tools package if needed)." fi echo "" # 3. Routing Table section_header "ROUTING TABLE" echo "Using 'ip route show':" ip route show echo "" if command -v netstat >/dev/null 2>&1; then echo "Using 'netstat -rn':" netstat -rn else echo "netstat command not found (install net-tools package if needed)." fi echo "" # 4. DNS Configuration section_header "DNS CONFIGURATION" echo "Contents of /etc/resolv.conf:" cat /etc/resolv.conf echo "" # 5. DHCP Lease Information section_header "DHCP LEASE INFORMATION" LEASE_DIR="/var/lib/dhcp" if [ -d "$LEASE_DIR" ]; then foundLease=0 for lease_file in "$LEASE_DIR"/dhclient*.leases; do if [ -f "$lease_file" ]; then echo ">> Lease file: $lease_file" cat "$lease_file" echo "--------------------------------------" foundLease=1 fi done if [ $foundLease -eq 0 ]; then echo "No DHCP lease files found in $LEASE_DIR." fi else echo "DHCP lease directory $LEASE_DIR does not exist." fi echo "" # Additionally, check syslog for recent DHCP-related messages. section_header "DHCP MESSAGES (SYSLOG)" if [ -f /var/log/syslog ]; then grep -i dhcp /var/log/syslog | tail -n 30 else echo "/var/log/syslog not found." fi echo "" # 6. ARP Table section_header "ARP TABLE" ip neighbor show echo "" # 7. Interface Statistics section_header "INTERFACE STATISTICS" ip -s link echo "" # 8. Active Network Connections section_header "ACTIVE NETWORK CONNECTIONS" if command -v ss >/dev/null 2>&1; then ss -tulwn elif command -v netstat >/dev/null 2>&1; then netstat -tulwn else echo "Neither ss nor netstat found." fi echo "" # 9. Internet Connectivity Tests section_header "INTERNET CONNECTIVITY TESTS" echo "Ping (IPv4) test to 8.8.8.8:" ping -c 4 8.8.8.8 echo "" echo "DNS resolution test (ping google.com):" ping -c 4 google.com echo "" # 10. External IP Detection section_header "EXTERNAL IP ADDRESS" if command -v curl >/dev/null 2>&1; then echo "Your external IP (via https://api.ipify.org):" curl -s https://api.ipify.org echo "" elif command -v wget >/dev/null 2>&1; then echo "Your external IP (via https://api.ipify.org):" wget -qO- https://api.ipify.org echo "" else echo "Neither curl nor wget is installed. Install one to detect your external IP." fi echo "" # 11. Traceroute section_header "TRACEROUTE TO google.com" if command -v traceroute >/dev/null 2>&1; then traceroute google.com else echo "traceroute command not found. Install it with 'sudo apt install traceroute'." fi echo "" # 12. iptables (Firewall Rules) section_header "IPTABLES FIREWALL RULES" if command -v iptables >/dev/null 2>&1; then sudo iptables -L -n -v else echo "iptables command not found." fi echo "" # 13. NetworkManager (if applicable) if command -v nmcli >/dev/null 2>&1; then section_header "NETWORKMANAGER DEVICE INFORMATION" nmcli device show echo "" fi section_header "DIAGNOSTICS COMPLETE" echo "The network diagnostics report is complete." exit 0