Why My Home Internet Was Suddenly Slow — And How I Found Out It Was the ISP

Recently I ran into a frustrating issue: my home network became painfully slow. Websites I visit every day — like Google and GitHub — were loading inconsistently, sometimes not loading at all. At first, I thought something was wrong with my router or my local setup. But after a series of step-by-step tests, I discovered the real culprit: my ISP.

This post documents how I diagnosed the problem, what I learned about ISPs and connection types in Australia, and some tips you can use to avoid the same headaches.

Symptoms: Slow Access to Google & GitHub

It started with weird latency spikes. Both Google and GitHub became slow to load, and occasionally the browser would just give up with a timeout. But interestingly, once I connected to a VPN (with a server hosted on AWS), everything suddenly became fast and reliable again.

That was my first hint — if a VPN fixes the problem, then something in the path between me and the ISP must be the issue.

Testing Isolations: Wired, Single Device, Same Results

To eliminate any possibility of home-network congestion, I disconnected my Wi-Fi entirely and connected only my laptop to the router via Ethernet. No other devices were using the network.

Yet the results were identical:

  • Normal traffic → Slow / unstable
  • VPN traffic → Fast / reliable

The problem wasn’t Wi-Fi, wasn’t my laptop, wasn’t my router, and wasn’t local congestion. It was upstream.

Tracing the Problem: ISP Gateway Responding Slowly

By breaking things down one step at a time — checking routes, checking DNS, running traceroute and mtr — I eventually identified the real bottleneck:

The ISP’s gateway was returning very slowly.

This also explained why switching to a faster public DNS resolver like 1.1.1.1 (Cloudflare) temporarily improved things — the DNS request was quick, but the actual routing still suffered from the slow gateway.

Switching DNS wasn’t the fix; it only masked the symptoms slightly.

Diagram 1: Simplified network flow

Laptop → Home Router → ISP Gateway → Internet
         ↑                 ↑
       Slow?             VPN fixes speed

Switching ISP: Immediate Improvement

After confirming the issue was beyond my local control, I switched to another NBN provider.

Instantly, all the latency issues disappeared. Everything — including Google and GitHub — went back to being fast and consistent.

And that’s when I started digging deeper into how NBN actually works under different ISPs.

PPPoE vs IPoE: The Two NBN Connection Types That Matter

Even though everyone in Australia uses "NBN", there are still two very different ways ISPs connect customers:

1. PPPoE (Point-to-Point Protocol over Ethernet)

The old-school method. Works almost like a VPN tunnel. Requires a username and password.

Characteristics:

  • Higher overhead
  • Requires per-session authentication
  • Can bottleneck at the ISP’s PPPoE gateway server
  • Often congested during peak hours
  • MTU is usually restricted to 1480 bytes

2. IPoE (DHCP-based)

The modern method. No username/password — just plug and play.

Characteristics:

  • Lower overhead
  • No per-user PPPoE tunnel
  • No PPPoE gateway bottleneck
  • Typically supports full 1500 MTU end-to-end

Diagram 2: PPPoE vs IPoE simplified

PPPoE:
Laptop → Router → PPPoE Gateway → Internet

IPoE:
Laptop → Router → Internet (no gateway bottleneck)

In daily use, this difference matters much more than people realise.

MTU: The Hidden Performance Killer

One of the worst issues with PPPoE is the reduced MTU:

  • In PPPoE: 1480 bytes
  • In local networks and IPoE: 1500 bytes

If your router or devices aren’t configured correctly, this mismatch causes:

  • Packet fragmentation
  • Retransmissions
  • “First request always fails” behaviour
  • Higher latency
  • Slower perceived loading

With IPoE, the MTU is consistent at 1500 bytes, which avoids these issues entirely.

Diagram 3: MTU mismatch impact

PPPoE MTU 1480  vs Local 1500
---------------------------------
Packet size > 1480 → Fragmented
1st request often fails → Retry → Higher latency

Conclusion: ISP Choice Matters More Than You Think

Your NBN provider isn’t just selling “speed” — they’re providing an entire connection architecture. And it turns out that architecture has a huge effect on real-world experience.

Here’s what I learned:

  1. Choose an ISP that uses IPoE, not PPPoE.
  2. Test their gateway response time — it can be the hidden bottleneck.
  3. Use tools like traceroute, mtr, and ping to diagnose slow connections.
  4. If connecting via a VPN makes things faster, your ISP is likely the problem.
  5. Do a quick search to see which connection method your ISP uses.

Appendix: How to Check Which Connection Method Your NBN Provider Uses

If you’re in Australia, there’s a simple and surprisingly reliable way to find out whether your ISP uses PPPoE or IPoE:

Search Google for: does <ISP name> use PPPoE

Often the first result — even if AI-generated — is accurate. You can also skim the top few results (forums, Whirlpool threads, ISP support pages) to confirm.

Most providers openly state it because it determines:

  • Whether you need a username/password
  • What MTU you should configure
  • Whether you’ll be dealing with gateway bottlenecks

This one quick search can save you a lot of debugging later.

Appendix: Some Common Australian NBN ISPs and Their Connection Types

Here’s a more up-to-date (as of 2024–2025) table listing a number of major Australian NBN ISPs and their typical connection method (PPPoE vs IPoE), based on publicly available and Whirlpool-sourced data. Source: Whirlpool’s “NBN Modem Routers ISP Settings” page.

ISP Typical NBN Connection Type Notes
Aussie Broadband IPoE (DHCP / Auto IP) No login required. (Whirlpool)
Belong IPoE (DHCP) No login required. (Whirlpool)
Optus IPoE (DHCP) According to Whirlpool guide. (Whirlpool)
iiNet PPPoE (legacy) PPPoE for many VDSL connections; older or legacy plans may differ. (iiNet)
Internode PPPoE Listed in Whirlpool ISP settings. (Whirlpool)
Exetel Mixed: PPPoE (legacy) / IPoE (new) Older connections use PPPoE; most new connections are IPoE. (Whirlpool)
Kogan PPPoE Older documentation shows IPoE; current protocol is PPPoE. (Whirlpool)
Launtel IPoE (DHCP) MTU 1500, no PPPoE login needed. (Whirlpool)
Leaptel IPoE (DHCP) No login required. (Whirlpool)
Superloop IPoE (DHCP) No login required. (Whirlpool)
Telstra (NBN) IPoE (DHCP) No username/password for most NBN plans. (Whirlpool)
SpinTel PPPoE Requires PPPoE login. (Whirlpool)
More Telecom PPPoE (some new IPoE) Newer connections offered with IPoE; older customers may still be on PPPoE. (Reddit)
Vodafone (NBN) PPPoE PPPoE with login required. (Whirlpool)
Neptune Internet IPoE (DHCP) IPoE for faster speeds and simpler authentication. (Neptune)