How to Monitor Network Routing Table Changes

How to Monitor Network Routing Table Changes

Need to monitor network routing table changes on your Linux server? Want to track routing table modifications, detect routing changes, and verify routing configuration? This guide shows you how to monitor routing table changes using built-in commands and automated monitoring with Zuzia.app.

For comprehensive routing monitoring strategies, see Network Routing and Connectivity Monitoring Guide. For troubleshooting routing issues, see Network Routing Misconfiguration.

Why Monitoring Routing Table Changes Matters

Routing tables determine how network traffic is routed. When routing tables change unexpectedly, network connectivity can be disrupted, traffic can be misrouted, and services can become unreachable. Monitoring routing table changes helps you detect unauthorized modifications, track routing configuration, maintain network connectivity, and ensure routing tables remain correct.

Method 1: View Current Routing Table

View current routing table to understand current configuration:

Display Routing Table

# View routing table
ip route

# View routing table with details
ip route show

# View routing table in table format
route -n

# Display default gateway
ip route | grep default

Analyze Routing Information

# View routes for specific network
ip route show 192.168.1.0/24

# View routes via specific interface
ip route show dev eth0

# Display routing table statistics
ip route show | wc -l

# View default route
ip route | grep "^default"

Method 2: Compare Routing Tables

Compare current routing table with previous configurations to detect changes:

Compare with Previous Configuration

# Save current routing table
ip route > /tmp/routes-current-$(date +%Y%m%d-%H%M%S).txt

# Compare with previous routing table
diff /tmp/routes-previous.txt /tmp/routes-current.txt

# Check for route additions
comm -13 <(sort /tmp/routes-old.txt) <(sort <(ip route))

# Check for route removals
comm -23 <(sort /tmp/routes-old.txt) <(sort <(ip route))

Detect Routing Changes

# Check if routing table matches expected configuration
ip route | diff - /backup/routes-baseline.txt

# Verify critical routes exist
ip route | grep -q "^default" && echo "Default route exists" || echo "No default route"

# Check for unexpected routes
ip route | grep -v "^default\|^192.168\|^10\." | head -10

Method 3: Monitor Routing Changes

Monitor routing changes over time to track modifications:

Track Routing Modifications

# Save routing table with timestamp
ip route > /tmp/routes-$(date +%Y%m%d-%H%M%S).txt

# Compare with baseline
diff /backup/routes-baseline.txt /tmp/routes-current.txt

# Monitor routing table size
ip route show | wc -l

# Track routing table changes
watch -n 1 'ip route show | wc -l'

Detect Unauthorized Changes

# Check for routing table modifications
ip route show > /tmp/routes-current.txt
diff /tmp/routes-baseline.txt /tmp/routes-current.txt

# Verify routing configuration consistency
ip route | awk '{print $1}' | sort | uniq -d

# Check for duplicate routes
ip route show | awk '{print $1, $3}' | sort | uniq -d

Method 4: Automated Routing Change Monitoring with Zuzia.app

While manual routing checks work for troubleshooting, production Linux servers require automated routing change monitoring that continuously tracks routing tables, detects changes, and alerts you when routing configurations are modified.

How Zuzia.app Routing Change Monitoring Works

Zuzia.app automatically monitors routing table changes through scheduled command execution. The platform checks routing tables, compares with previous configurations, detects changes, and sends alerts when modifications are detected.

Setting Up Routing Change Monitoring

1. Add Scheduled Task for Routing Table Monitoring

   • Command: ip route show > /tmp/routes-current.txt && diff /tmp/routes-baseline.txt /tmp/routes-current.txt || echo "No changes"
   • Frequency: Every 15 minutes
   • Alert when: Routing table changes detected

2. Configure Default Route Verification

   • Command: ip route | grep -q "^default" && echo "OK" || echo "CRITICAL: No default route"
   • Frequency: Every 10 minutes
   • Alert when: Default route missing

3. Set Up Routing Table Comparison

   • Command: ip route show | diff - /backup/routes-baseline.txt
   • Frequency: Every 30 minutes
   • Alert when: Routing differences detected

Custom Routing Monitoring Commands

Add these commands as scheduled tasks:

# Check routing table
ip route show

# Verify default route
ip route | grep "^default"

# Monitor routing changes
ip route show | diff - /backup/routes-baseline.txt

# Check routing table size
ip route show | wc -l

Best Practices

1. Monitor Routing Tables Continuously

Use Zuzia.app for continuous routing monitoring. Set up alerts before routing issues become critical. Review routing tables regularly.

2. Maintain Routing Baselines

Keep accurate routing table baselines. Store baselines in version control. Update baselines when authorized changes occur.

3. Track All Routing Changes

Monitor all routing table modifications. Track authorized changes. Detect unauthorized changes. Document change procedures.

Troubleshooting

Routing Table Changes Detected

When routing changes are detected:

1. Review current routing table: ip route show
2. Compare with baseline: diff /backup/routes-baseline.txt <(ip route)
3. Verify changes are authorized
4. Restore routing if unauthorized

Default Route Missing

When default route is missing:

1. Check routing table: ip route | grep default
2. Verify network interface: ip link show
3. Restore default route if needed: ip route add default via GATEWAY

FAQ

Related guides, recipes, and problems

• Related guides

  • Network Routing and Connectivity Monitoring Guide
  • Server Performance Monitoring Best Practices

• Related recipes

  • Check Network Port Security
  • Monitor Network Bandwidth Usage

• Related problems

  • Network Routing Misconfiguration
  • Firewall Rules Blocking Legitimate Traffic