Network Routing Misconfiguration - Troubleshooting Guide

Network Routing Misconfiguration - Troubleshooting Guide

Network connectivity broken, routes are incorrect, services unreachable. This guide gives you immediate steps to diagnose and fix network routing misconfiguration—now. No theory, just action.

For setting up monitoring to prevent this in the future, see Network Routing and Connectivity Monitoring Guide after you've resolved the immediate crisis.

60-Second Triage

Run these commands in order:

# Step 1: Check routing table (takes 5 seconds)
ip route

# Step 2: Test connectivity (takes 5 seconds)
ping -c 4 8.8.8.8

# Step 3: Check default gateway (takes 5 seconds)
ip route | grep default

# Step 4: View routing errors (takes 10 seconds)
dmesg | grep -i "route\|routing" | tail -20

Common Routing Issues and Quick Fixes

Symptoms of Routing Misconfiguration

Routing misconfiguration manifests in several ways:

• No internet connectivity: Can't reach external networks
• Services unreachable: Can't access services on other networks
• Intermittent connectivity: Some routes work, others don't
• Routing errors: Kernel messages show routing errors

Step-by-Step Troubleshooting

Step 1: Identify Routing Problems

When network connectivity is broken:

1. Check Routing Table:

   ip route
   

2. Verify Default Gateway:

   ip route | grep default
   

3. Test Connectivity:

   ping -c 4 8.8.8.8
   ping -c 4 $(ip route | grep default | awk '{print $3}')
   

Step 2: Investigate Routing Issues

Once you identify routing problems:

1. Check Network Interfaces:

   ip link show
   ip addr show
   

2. View Routing Errors:

   dmesg | grep -i "route\|routing" | tail -20
   

3. Check Route Conflicts:

   ip route | awk '{print $1}' | sort | uniq -d
   

Step 3: Fix Routing Configuration

When routing issues are identified:

1. Add Missing Default Route:

   sudo ip route add default via GATEWAY_IP
   

2. Fix Incorrect Gateway:

   sudo ip route del default
   sudo ip route add default via CORRECT_GATEWAY
   

3. Restore Routing Configuration:

   sudo systemctl restart networking
   

Step 4: Prevent Future Routing Issues

To prevent routing misconfiguration:

1. Monitor Routing Continuously:

   • Use Zuzia.app to monitor routing tables
   • Set up alerts for routing changes
   • Track routing configuration

2. Maintain Routing Documentation:

   • Document all routing configurations
   • Maintain routing change logs
   • Update documentation when routes change

Automatic Detection with Zuzia.app

Zuzia.app automatically monitors routing and detects misconfiguration:

• Checks routing tables every few minutes
• Detects routing changes immediately
• Sends alerts when routing issues occur
• Tracks routing configuration over time

Set up routing monitoring in Zuzia.app to prevent misconfiguration:

1. Add scheduled task: ip route | grep -q "^default" && echo "OK" || echo "FAIL"
2. Configure alerts for routing issues
3. Monitor routing continuously

Best Practices for Preventing Routing Misconfiguration

1. Monitor Routing Continuously

Don't wait for routing issues:

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

2. Test Routing Changes

Test routing changes before production:

• Verify routes work correctly
• Test connectivity after changes
• Document routing procedures

3. Maintain Routing Documentation

Keep routing documentation current:

• Document all routing configurations
• Maintain routing change logs
• Update documentation when routes change

FAQ: Common Questions About Routing Misconfiguration

How do I know if routing is misconfigured?

Check routing table: ip route. Test connectivity: ping -c 4 8.8.8.8. Verify default gateway: ip route | grep default. Check routing errors: dmesg | grep -i "route\|routing".

What should I do immediately when routing is misconfigured?

Immediately check routing table: ip route. Verify default gateway: ip route | grep default. Add missing default route: sudo ip route add default via GATEWAY. Test connectivity: ping -c 4 8.8.8.8.

Can routing misconfiguration cause complete network failure?

Yes, if default route is missing or incorrect, all external connectivity can be lost.

How can Zuzia.app help prevent routing misconfiguration?

Zuzia.app monitors routing tables continuously, detects routing changes immediately, sends alerts when routing issues occur, and tracks routing configuration over time.

Related guides, recipes, and problems

• Related guides

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

• Related recipes

  • Monitor Network Routing Table Changes
  • Check Network Port Security

• Related problems

  • Firewall Rules Blocking Legitimate Traffic
  • Configuration Drift Causing Issues