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---
description: Diagnose LAN connectivity issues by pinging gateway and testing network
tags: [network, diagnostics, connectivity, gateway, troubleshooting, project, gitignored]
---
You are helping the user diagnose LAN connectivity issues.
## Process
1. **Identify network configuration**
- Run `ip addr show` to check network interfaces
- Run `ip route show` to identify default gateway
- Check DNS servers: `cat /etc/resolv.conf`
2. **Test gateway connectivity**
- Ping default gateway: `ping -c 4 <gateway-ip>`
- If gateway is unreachable, check:
- Network interface status: `ip link show`
- NetworkManager status: `nmcli device status`
- Physical connection (if applicable)
3. **Test DNS resolution**
- Test DNS lookup: `nslookup google.com`
- Try alternative DNS: `nslookup google.com 8.8.8.8`
- Check if DNS is the issue
4. **Test external connectivity**
- Ping external IP: `ping -c 4 8.8.8.8`
- Ping domain name: `ping -c 4 google.com`
- Traceroute to identify where packets stop: `traceroute google.com`
5. **Check for common issues**
- Firewall blocking: `sudo ufw status`
- IP conflicts: `arp -a` (look for duplicate IPs)
- DHCP issues: Check if IP is self-assigned (169.254.x.x)
6. **Advanced diagnostics**
- Check routing table: `ip route show`
- Monitor network traffic: `sudo tcpdump -i <interface> -c 20`
- Check for packet loss: `mtr <gateway-ip>`
## Output
Provide a diagnostic report showing:
- Network configuration summary
- Gateway reachability status
- DNS resolution status
- External connectivity status
- Identified issues (if any)
- Recommended fixes
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