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🗓️ 04102025 0030
📎 networking_dns_tools

CONNECTIVITY & NETWORK PATH TOOLS

Tools for testing if hosts are reachable and tracing network paths.

ping - Test Connectivity​

Commands​

ping example.com              # Basic ping (infinite)
ping -c 4 example.com        # Send 4 packets only
ping -i 2 example.com        # 2 second interval
ping -t 5 example.com        # Set TTL (Time To Live)
ping -s 1000 example.com     # Set packet size (bytes)

Use for: Testing if host is reachable, measuring latency and packet loss.

What it does: Sends ICMP (Internet Control Message Protocol) echo request packets and waits for replies.

Interpreting Output​

$ ping -c 4 google.com
PING google.com (142.250.185.78): 56 data bytes
64 bytes from 142.250.185.78: icmp_seq=0 ttl=117 time=12.4 ms
64 bytes from 142.250.185.78: icmp_seq=1 ttl=117 time=11.8 ms
64 bytes from 142.250.185.78: icmp_seq=2 ttl=117 time=13.1 ms
64 bytes from 142.250.185.78: icmp_seq=3 ttl=117 time=12.0 ms

--- google.com ping statistics ---
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 11.8/12.3/13.1/0.5 ms

Key parts:

  • 64 bytes from...: Successful reply received
  • icmp_seq: Sequence number (should increment 0, 1, 2, 3...)
  • ttl: Time To Live - hops remaining (starts at ~64 or ~128, decrements each hop)
  • time: Round-trip time in milliseconds (latency)
  • Statistics:
    • 0.0% packet loss - Perfect (0% = good, >5% = concerning)
    • min/avg/max - Latency range
    • stddev - Consistency (low = stable, high = jittery)

Common issues:

  • Request timeout: No response (host down, firewall blocking, or network issue)
  • Unknown host: DNS can't resolve name (use networking_dns_tools to investigate)
  • High latency (>100ms): Slow connection
  • Packet loss: Unstable connection (use networking_advanced_debugging for deep analysis)
  • Destination Host Unreachable: Router can't find route to host

Good latency values:

  • < 20ms - Excellent (local network or nearby server)
  • 20-50ms - Good (regional)
  • 50-100ms - Acceptable (international)
  • > 100ms - Slow (distant server or congestion)

traceroute - Trace Network Path​

Commands​

traceroute example.com       # See route to host (Linux/Mac)
tracert example.com          # Windows version
traceroute -n example.com    # Faster (no DNS resolution)
traceroute -m 20 example.com # Max 20 hops (default 30)
traceroute -q 1 example.com  # 1 query per hop (faster)

Use for: Finding where connection fails, diagnosing slow connections, understanding network topology.

What it does: Shows the route packets take to reach a destination by sending packets with increasing TTL values.

Interpreting Output​

$ traceroute google.com
traceroute to google.com (142.250.185.78), 30 hops max, 60 byte packets
 1  192.168.1.1 (192.168.1.1)  1.234 ms  1.123 ms  1.056 ms
 2  10.0.0.1 (10.0.0.1)  5.678 ms  5.432 ms  5.890 ms
 3  isp-gateway.net (203.0.113.1)  12.456 ms  12.234 ms  12.567 ms
 4  * * *
 5  142.250.185.78 (142.250.185.78)  18.234 ms  17.890 ms  18.456 ms

Key parts:

  • Hop number (1, 2, 3...): Each router along the path
  • IP address/hostname: The router at this hop
  • Three time values: Round-trip time for 3 probes (shows consistency)
  • * * *: Timeout (router not responding to traceroute, but still forwarding packets)

Reading the path:

  1. Hop 1: Your router/gateway (usually 192.168.x.x or 10.x.x.x)
  2. Hop 2-3: Your ISP's routers
  3. Middle hops: Internet backbone routers
  4. Last hop: Destination server

Troubleshooting with traceroute:

  • Connection dies at specific hop: That router is the problem
  • Sudden latency spike: Congestion or long-distance link starting at that hop
  • * * * for all hops after X: Firewall blocking ICMP after hop X (doesn't mean packets aren't getting through)
  • Asymmetric routing: Path there ≠ path back (normal, just FYI)

Example diagnosis:

 1  router.local (192.168.1.1)     1 ms   1 ms   1 ms   ✅ Local network fine
 2  isp.gateway (10.0.0.1)         5 ms   5 ms   5 ms   ✅ ISP connection fine  
 3  * * *                                                ⚠️ Router not responding (OK)
 4  remote.net (203.0.113.1)     500 ms 498 ms 502 ms   ❌ High latency! Problem here

References​