Configure network interface monitoring with ICMP ping and connectivity testing

Update system packages

Start by updating your package manager to ensure you get the latest monitoring tools and dependencies.

sudo apt update && sudo apt upgrade -y

sudo dnf update -y

Install ping monitoring tools

Install the essential network monitoring utilities including advanced ping tools, mail utilities for alerts, and system monitoring packages.

sudo apt install -y iputils-ping fping hping3 mailutils postfix bc

sudo dnf install -y iputils fping hping3 mailx postfix bc

Configure mail system for alerts

Set up a basic mail configuration to send email alerts when connectivity issues are detected.

sudo dpkg-reconfigure postfix

Select "Internet Site" and enter your domain name. For production systems, configure with your actual SMTP relay.

Create monitoring directory structure

Set up organized directories for monitoring scripts, logs, and configuration files with proper permissions.

sudo mkdir -p /opt/network-monitor/{scripts,logs,config}
sudo mkdir -p /var/log/network-monitor
sudo chown root:root /opt/network-monitor
sudo chmod 755 /opt/network-monitor
sudo chmod 755 /opt/network-monitor/{scripts,logs,config}

Create ping monitoring configuration

Define the targets and thresholds for your network monitoring. This configuration includes internal gateways, external DNS servers, and critical services.

# Network monitoring targets configuration
Format: TARGET_NAME:IP_ADDRESS:DESCRIPTION
DEFAULT_GATEWAY:192.168.1.1:Local network gateway
DNS_PRIMARY:8.8.8.8:Google DNS primary
DNS_SECONDARY:1.1.1.1:Cloudflare DNS
INTERNET_CHECK:203.0.113.1:External connectivity test
LOCAL_SERVER:192.168.1.100:Internal application server

Monitoring thresholds
PING_TIMEOUT=5
FAIL_THRESHOLD=3
CHECK_INTERVAL=60
ALERT_EMAIL=admin@example.com

Create the main monitoring script

Build a comprehensive monitoring script that performs ping tests, tracks failures, and sends alerts when thresholds are exceeded.

#!/bin/bash

Network Interface Ping Monitor
Monitors network connectivity and sends alerts on failures

CONFIG_FILE="/opt/network-monitor/config/targets.conf"
LOG_FILE="/var/log/network-monitor/ping-monitor.log"
STATE_DIR="/opt/network-monitor/logs"
DATE=$(date '+%Y-%m-%d %H:%M:%S')

Load configuration
source "$CONFIG_FILE"

Function to log messages
log_message() {
    echo "[$DATE] $1" >> "$LOG_FILE"
}

Function to send email alert
send_alert() {
    local target="$1"
    local status="$2"
    local message="$3"
    
    subject="Network Alert: $target $status"
    
    {
        echo "Network Monitoring Alert"
        echo "========================"
        echo "Target: $target"
        echo "Status: $status"
        echo "Time: $DATE"
        echo "Message: $message"
        echo ""
        echo "Server: $(hostname)"
        echo "IP Address: $(hostname -I | awk '{print $1}')"
    } | mail -s "$subject" "$ALERT_EMAIL"
}

Function to test connectivity
test_connectivity() {
    local name="$1"
    local ip="$2"
    local description="$3"
    local state_file="$STATE_DIR/${name}.state"
    
    # Perform ping test
    if ping -c 3 -W "$PING_TIMEOUT" "$ip" >/dev/null 2>&1; then
        # Success - reset failure counter
        echo "0" > "$state_file"
        log_message "SUCCESS: $name ($ip) - $description"
        
        # Check if this is recovery from failure
        if [ -f "$STATE_DIR/${name}.failed" ]; then
            send_alert "$name" "RECOVERED" "Connectivity to $ip ($description) has been restored"
            rm -f "$STATE_DIR/${name}.failed"
            log_message "RECOVERY: $name ($ip) connectivity restored"
        fi
    else
        # Failure - increment counter
        local fail_count=0
        if [ -f "$state_file" ]; then
            fail_count=$(cat "$state_file")
        fi
        
        fail_count=$((fail_count + 1))
        echo "$fail_count" > "$state_file"
        
        log_message "FAILURE: $name ($ip) - $description (attempt $fail_count)"
        
        # Send alert if threshold exceeded and not already alerted
        if [ "$fail_count" -ge "$FAIL_THRESHOLD" ] && [ ! -f "$STATE_DIR/${name}.failed" ]; then
            send_alert "$name" "FAILED" "Connectivity to $ip ($description) failed after $fail_count attempts"
            touch "$STATE_DIR/${name}.failed"
            log_message "ALERT: $name ($ip) threshold exceeded, alert sent"
        fi
    fi
}

Function to test network interfaces
test_interfaces() {
    log_message "Starting interface connectivity tests"
    
    # Read targets from config file
    while IFS=':' read -r name ip description; do
        # Skip comments and empty lines
        [[ "$name" =~ ^#.*$ ]] && continue
        [[ -z "$name" ]] && continue
        
        # Skip configuration variables
        [[ "$name" =~ ^[A-Z_]+=.*$ ]] && continue
        
        test_connectivity "$name" "$ip" "$description"
        sleep 1
    done < "$CONFIG_FILE"
    
    log_message "Interface connectivity tests completed"
}

Function to generate health report
generate_report() {
    local report_file="/var/log/network-monitor/daily-report-$(date +%Y%m%d).log"
    
    {
        echo "Network Health Report - $(date)"
        echo "======================================"
        echo ""
        
        echo "Current Interface Status:"
        ip -br addr show | grep -E "^(eth|ens|enp)" | while read iface state addr; do
            echo "  $iface: $state ($addr)"
        done
        
        echo ""
        echo "Routing Table:"
        ip route show | head -10
        
        echo ""
        echo "Current Connectivity Status:"
        while IFS=':' read -r name ip description; do
            [[ "$name" =~ ^#.*$ ]] && continue
            [[ -z "$name" ]] && continue
            [[ "$name" =~ ^[A-Z_]+=.*$ ]] && continue
            
            if ping -c 1 -W 2 "$ip" >/dev/null 2>&1; then
                echo "  ✓ $name ($ip): OK"
            else
                echo "  ✗ $name ($ip): FAILED"
            fi
        done < "$CONFIG_FILE"
        
        echo ""
        echo "Recent Failures (last 24 hours):"
        grep "FAILURE\|ALERT" "$LOG_FILE" | tail -20
        
    } > "$report_file"
    
    log_message "Daily health report generated: $report_file"
}

Main execution
case "${1:-monitor}" in
    "monitor")
        test_interfaces
        ;;
    "report")
        generate_report
        ;;
    "test")
        echo "Testing connectivity to all targets..."
        test_interfaces
        echo "Test completed. Check $LOG_FILE for results."
        ;;
    *)
        echo "Usage: $0 [monitor|report|test]"
        echo "  monitor: Run connectivity tests (default)"
        echo "  report:  Generate daily health report"
        echo "  test:    Run tests with console output"
        exit 1
        ;;
esac

Set script permissions

Configure proper permissions for the monitoring script to ensure it can execute but remains secure.

sudo chmod 755 /opt/network-monitor/scripts/ping-monitor.sh
sudo chown root:root /opt/network-monitor/scripts/ping-monitor.sh

Create advanced ping monitoring script

Build a secondary script that provides detailed network interface analysis and performance metrics.

#!/bin/bash

Network Interface Analyzer
Provides detailed interface statistics and performance metrics

LOG_FILE="/var/log/network-monitor/interface-analysis.log"
DATE=$(date '+%Y-%m-%d %H:%M:%S')

Function to analyze interface performance
analyze_interface() {
    local interface="$1"
    
    echo "Interface Analysis: $interface" >> "$LOG_FILE"
    echo "============================" >> "$LOG_FILE"
    echo "Timestamp: $DATE" >> "$LOG_FILE"
    
    # Interface status
    echo "Status: $(cat /sys/class/net/$interface/operstate 2>/dev/null || echo 'unknown')" >> "$LOG_FILE"
    
    # Get interface statistics
    if [ -d "/sys/class/net/$interface/statistics" ]; then
        echo "RX Packets: $(cat /sys/class/net/$interface/statistics/rx_packets)" >> "$LOG_FILE"
        echo "TX Packets: $(cat /sys/class/net/$interface/statistics/tx_packets)" >> "$LOG_FILE"
        echo "RX Bytes: $(cat /sys/class/net/$interface/statistics/rx_bytes)" >> "$LOG_FILE"
        echo "TX Bytes: $(cat /sys/class/net/$interface/statistics/tx_bytes)" >> "$LOG_FILE"
        echo "RX Errors: $(cat /sys/class/net/$interface/statistics/rx_errors)" >> "$LOG_FILE"
        echo "TX Errors: $(cat /sys/class/net/$interface/statistics/tx_errors)" >> "$LOG_FILE"
        echo "RX Dropped: $(cat /sys/class/net/$interface/statistics/rx_dropped)" >> "$LOG_FILE"
        echo "TX Dropped: $(cat /sys/class/net/$interface/statistics/tx_dropped)" >> "$LOG_FILE"
    fi
    
    # Ping test to gateway with detailed statistics
    local gateway=$(ip route | grep "^default.*$interface" | awk '{print $3}' | head -1)
    if [ -n "$gateway" ]; then
        echo "Gateway: $gateway" >> "$LOG_FILE"
        ping_result=$(ping -c 10 -i 0.2 "$gateway" 2>&1)
        echo "Gateway Ping Results:" >> "$LOG_FILE"
        echo "$ping_result" | grep -E "(packets transmitted|rtt)" >> "$LOG_FILE"
    fi
    
    echo "" >> "$LOG_FILE"
}

Main execution
echo "[$DATE] Starting interface analysis" >> "$LOG_FILE"

Analyze all active network interfaces
for interface in $(ip -br link show | grep -E "^(eth|ens|enp)" | awk '{print $1}'); do
    analyze_interface "$interface"
done

echo "[$DATE] Interface analysis completed" >> "$LOG_FILE"

Set permissions for analyzer script

Configure secure permissions for the interface analyzer script.

sudo chmod 755 /opt/network-monitor/scripts/interface-analyzer.sh
sudo chown root:root /opt/network-monitor/scripts/interface-analyzer.sh

Configure log rotation

Set up log rotation to prevent monitoring logs from consuming excessive disk space.

/var/log/network-monitor/*.log {
    daily
    rotate 30
    compress
    delaycompress
    missingok
    notifempty
    create 644 root root
    postrotate
        /bin/systemctl reload rsyslog > /dev/null 2>&1 || true
    endscript
}

Set up automated monitoring with cron

Configure cron jobs to run continuous monitoring, generate reports, and perform interface analysis. This ensures comprehensive network monitoring around the clock.

sudo crontab -e

Add the following cron entries:

# Network connectivity monitoring every minute
    * /opt/network-monitor/scripts/ping-monitor.sh monitor

Interface analysis every 5 minutes
/5    * /opt/network-monitor/scripts/interface-analyzer.sh

Daily health report at 6 AM
0 6   * /opt/network-monitor/scripts/ping-monitor.sh report

Weekly summary report (Sundays at 7 AM)
0 7   0 /opt/network-monitor/scripts/weekly-summary.sh

Create weekly summary script

Build a comprehensive weekly reporting script that analyzes trends and provides insights into network performance.

#!/bin/bash

Weekly Network Summary Report
Generates comprehensive weekly analysis

REPORT_FILE="/var/log/network-monitor/weekly-summary-$(date +%Y%m%d).log"
CONFIG_FILE="/opt/network-monitor/config/targets.conf"
LOG_FILE="/var/log/network-monitor/ping-monitor.log"

Load configuration
source "$CONFIG_FILE"

{
    echo "Weekly Network Summary Report"
    echo "Generated: $(date)"
    echo "======================================"
    echo ""
    
    # Summary statistics
    echo "Summary Statistics (Last 7 Days):"
    echo "----------------------------------"
    
    total_checks=$(grep -c "SUCCESS\|FAILURE" "$LOG_FILE" | tail -1)
    failures=$(grep -c "FAILURE" "$LOG_FILE" | tail -1)
    success_rate=$(echo "scale=2; ($total_checks - $failures) / $total_checks * 100" | bc)
    
    echo "Total connectivity checks: $total_checks"
    echo "Failures detected: $failures"
    echo "Success rate: ${success_rate}%"
    echo ""
    
    # Target-specific analysis
    echo "Per-Target Analysis:"
    echo "-------------------"
    while IFS=':' read -r name ip description; do
        [[ "$name" =~ ^#.*$ ]] && continue
        [[ -z "$name" ]] && continue
        [[ "$name" =~ ^[A-Z_]+=.*$ ]] && continue
        
        target_failures=$(grep "$name.*FAILURE" "$LOG_FILE" | wc -l)
        target_total=$(grep "$name.SUCCESS\|$name.FAILURE" "$LOG_FILE" | wc -l)
        
        if [ "$target_total" -gt 0 ]; then
            target_success_rate=$(echo "scale=2; ($target_total - $target_failures) / $target_total * 100" | bc)
            echo "$name ($ip): ${target_success_rate}% success rate ($target_failures failures)"
        fi
    done < "$CONFIG_FILE"
    
    echo ""
    echo "Critical Events This Week:"
    echo "-------------------------"
    grep "ALERT\|RECOVERY" "$LOG_FILE" | tail -20
    
    echo ""
    echo "Interface Statistics:"
    echo "-------------------"
    for interface in $(ip -br link show | grep -E "^(eth|ens|enp)" | awk '{print $1}'); do
        if [ -d "/sys/class/net/$interface" ]; then
            state=$(cat "/sys/class/net/$interface/operstate" 2>/dev/null || echo "unknown")
            rx_errors=$(cat "/sys/class/net/$interface/statistics/rx_errors" 2>/dev/null || echo "0")
            tx_errors=$(cat "/sys/class/net/$interface/statistics/tx_errors" 2>/dev/null || echo "0")
            echo "$interface: $state (RX errors: $rx_errors, TX errors: $tx_errors)"
        fi
    done
    
} > "$REPORT_FILE"

Email the weekly report
if [ -n "$ALERT_EMAIL" ]; then
    mail -s "Weekly Network Summary - $(hostname)" "$ALERT_EMAIL" < "$REPORT_FILE"
fi

echo "Weekly summary generated: $REPORT_FILE"

Set permissions for weekly summary script

Configure proper permissions for the weekly summary script.

sudo chmod 755 /opt/network-monitor/scripts/weekly-summary.sh
sudo chown root:root /opt/network-monitor/scripts/weekly-summary.sh

Create systemd service for monitoring

For more reliable monitoring, create a systemd service that can be managed and monitored by the system.

[Unit]
Description=Network Interface Ping Monitor
After=network.target

[Service]
Type=simple
ExecStart=/opt/network-monitor/scripts/ping-monitor.sh monitor
ExecReload=/bin/kill -HUP $MAINPID
Restart=always
RestartSec=60
User=root
Group=root

Security settings
PrivateTmp=true
ProtectSystem=strict
ReadWritePaths=/var/log/network-monitor /opt/network-monitor/logs

[Install]
WantedBy=multi-user.target

Enable and start the monitoring service

Enable the systemd service to ensure monitoring starts automatically on boot.

sudo systemctl daemon-reload
sudo systemctl enable network-monitor.service
sudo systemctl start network-monitor.service
sudo systemctl status network-monitor.service