Troubleshooting wget Connection Timeouts: Network and DNS Debugging Guide


2 views

When wget hangs with connection timeouts for a specific URL while other URLs work fine, we're typically dealing with either:

  • Network routing problems
  • DNS resolution issues
  • Firewall restrictions
  • Server-side IP filtering

Let's perform some fundamental network diagnostics:

# Check basic connectivity
ping -c 4 www.fcc-fac.ca

# Test TCP connection on port 80
timeout 10 telnet www.fcc-fac.ca 80

# Alternative method using netcat
nc -zv -w 10 www.fcc-fac.ca 80

The fact that some hosts work while others don't suggests potential DNS issues:

# Check all DNS records
dig www.fcc-fac.ca ANY

# Compare with other working domains
dig working-domain.com ANY

# Test with different DNS servers
dig @8.8.8.8 www.fcc-fac.ca
dig @1.1.1.1 www.fcc-fac.ca

When traceroute shows asterisks (*), we need alternative tools:

# More detailed path analysis
mtr --report --report-cycles 5 www.fcc-fac.ca

# TCP-specific traceroute
sudo tcptraceroute -n -w 2 www.fcc-fac.ca 80

# Check for MTU issues
ping -M do -s 1472 www.fcc-fac.ca

Try these wget variations to bypass potential issues:

# Force IPv4 only
wget -4 -T 10 http://www.fcc-fac.ca

# Force IPv6 only
wget -6 -T 10 http://www.fcc-fac.ca

# Use specific DNS server
wget --header="Host: www.fcc-fac.ca" http://[IP_ADDRESS]

Create a shell script to test multiple endpoints:

#!/bin/bash
ENDPOINTS=("65.87.238.35" "207.195.108.140" "alternative-ip-if-available")
TIMEOUT=5

for ip in "${ENDPOINTS[@]}"; do
  echo "Testing $ip..."
  if curl --max-time $TIMEOUT --connect-timeout $TIMEOUT --silent --show-error \
    --header "Host: www.fcc-fac.ca" "http://$ip" &>/dev/null; then
    echo "Success with $ip"
    exit 0
  fi
done
echo "All endpoints failed"
exit 1

Examine these critical network settings:

# Check system DNS configuration
cat /etc/resolv.conf

# Verify routing table
ip route show

# Inspect firewall rules
sudo iptables -L -n -v

# Check system-wide connection tracking
ss -tulnp

For deep network debugging, capture actual packets:

# Basic capture (Ctrl+C to stop)
sudo tcpdump -i any host www.fcc-fac.ca -w capture.pcap

# Filtered capture focusing on connection attempts
sudo tcpdump -i any 'tcp port 80 and (host 65.87.238.35 or host 207.195.108.140)' -v

When wget fails for a specific URL while working fine for others, and the problematic URL works from other machines, we're typically dealing with one of these scenarios:

  • Network path issues (routing, firewalls)
  • DNS resolution problems
  • IP-based blocking
  • MTU size mismatches
  • TCP/IP stack issues

Let's systematically diagnose the issue:

# First check basic connectivity
ping www.fcc-fac.ca

# Test raw TCP connection
nc -zv www.fcc-fac.ca 80
telnet www.fcc-fac.ca 80

# Check DNS resolution
dig www.fcc-fac.ca
host www.fcc-fac.ca

# Advanced network testing
mtr --report --report-cycles 10 www.fcc-fac.ca

Based on your traceroute showing packets dropping after hop 9, these approaches often help:

1. Check Local Firewall Rules

sudo iptables -L -n -v
sudo ufw status  # If using UFW

2. Test Alternative Connection Methods

# Try different protocols
wget --no-check-certificate https://www.fcc-fac.ca

# Force IPv4 or IPv6
wget -4 http://www.fcc-fac.ca
wget -6 http://www.fcc-fac.ca

3. Adjust TCP Parameters

# Try different TCP window sizes
wget --tries=1 --timeout=10 --waitretry=1 --bind-address=YOUR_IP http://www.fcc-fac.ca

# Check current settings
sysctl net.ipv4.tcp_window_scaling

When basic checks don't reveal the issue, try these advanced techniques:

Packet Capture Analysis

sudo tcpdump -i eth0 host www.fcc-fac.ca -w capture.pcap
# Analyze with Wireshark or:
tcpdump -r capture.pcap -n

MTU Path Discovery

ping -M do -s 1472 www.fcc-fac.ca  # Adjust size down until successful

Proxy Testing

wget -e use_proxy=yes -e http_proxy=proxy.example.com:8080 http://www.fcc-fac.ca

After making changes, verify with:

wget --spider --timeout=10 --tries=1 http://www.fcc-fac.ca
curl -Iv --connect-timeout 10 http://www.fcc-fac.ca

Remember that intermittent network issues might require persistent testing over time to identify patterns.