Hands-On: See the Internet in Action

These exercises use free tools that work on any smartphone browser. You do not need to install anything.

Exercise 1 — Find Your Public IP Address

Before You Start: Your phone has a private IP on your mobile network and a public IP that the internet sees. This exercise shows you the public one.

  1. Open your phone’s browser (Chrome, Firefox, or Safari)
  2. Go to toolbox.googleapps.com
  3. Tap Check MX in the top menu — then look for Check Header (or search for “what is my ip” in any search engine)
  4. Alternatively, go to whatismyip.com — your public IP appears at the top of the page
  5. Note the IP address shown
  6. Now switch from mobile data to Wi-Fi (or vice versa) and check again

What You’re Seeing

The two IP addresses are different because your mobile network and your home Wi-Fi connect to the internet through different routers, each with its own public IP. The internet sees your traffic coming from that router’s IP, not from your phone’s private IP.

Discussion Prompt: If two phones on the same Wi-Fi network both visit google.com, which IP does Google see? The router’s public IP — the same one for both phones.

Exercise 2 — Watch DNS Work

Before You Start: DNS translates names to IP addresses. This exercise lets you see that translation happen for different domain names around the world.

  1. Open your browser and go to dnschecker.org
  2. In the search box, type sbi.co.in and tap the search button
  3. Wait for the results to load — you will see a map and a list of IP addresses
  4. Note the IP address shown for India
  5. Now search for google.com — note how many different IP addresses appear (Google uses many servers worldwide)
  6. Now search for irctc.co.in

What You’re Seeing

Each domain name maps to one or more IP addresses. Google shows many different IPs because they have servers in data centres all over the world — when you connect to Google, you are routed to the nearest one. IRCTC likely shows fewer IPs because their infrastructure is more centralised in India.

Security Note

DNS is not encrypted by default. This means anyone on your network — your ISP, or an attacker on public Wi-Fi — can see which domain names you are looking up, even if the actual content is encrypted with HTTPS. This is why DNS-over-HTTPS (DoH) was invented, which we will touch on in Course 2.

Discussion Prompt: If an attacker could control the DNS response for sbi.co.in, what could they do with it?

Exercise 3 — Watch Packets Travel (Traceroute)

Before You Start: A traceroute shows you every router your data passes through on its way to a destination. Each router is one “hop.”

  1. Open your browser and go to ping.eu
  2. In the top menu, tap Traceroute
  3. In the hostname field, type google.com and tap Go
  4. Watch the results load — each numbered line is one hop
  5. Look at the response times in milliseconds (ms) for each hop
  6. Try the same with irctc.co.in — notice where the path diverges

What You’re Seeing

The hops with low response times (5–20 ms) are nearby routers — probably within your city or state. Hops with higher response times (50–150 ms) are farther away — possibly in another city or country. If a hop shows * * *, that router is configured to not respond to traceroute probes (common on backbone networks).

Deepa Asks

“Some hops show three times, like 12 ms, 15 ms, 11 ms — why three?”

The traceroute sends three separate packets to each hop, so you get three timing measurements. The variation is normal — it shows that network conditions fluctuate slightly even over milliseconds.

Discussion Prompt: When you do a traceroute from your phone in India to google.com, do the packets ever leave India? How can you tell?

Tying It Together

You have now seen the internet’s three fundamental mechanisms in action:

  • IP addresses — every device has one (Exercise 1)
  • DNS — names get translated to addresses (Exercise 2)
  • Routing — packets hop through multiple routers to reach their destination (Exercise 3)

Next session, we will ask the question that follows naturally from all of this: if your data is travelling through all those routers and networks — many of which you do not control — how do you keep it private and secure?