High latency when browsing web but dramatically reduces when using VPN

I generally have high latency when browsing web from my home internet connection. The connection itself is reasonably fast and I normally get ~120 Mbps of download speed, but the latency is often in the realm of several seconds.

The internet connection I use is a fiber by Australian NBN network and I live some 200m from the exchange. I'm located in Perth, Australia, but these latency issues exist even when accessing Australian websites.

Initially, I thought that the issue was with my modem/router which is a pretty cheap model. But when I use a VPN (through ExpressVPN) the latency issues disappear even when I use a VPN server that is physically very far away, say, Seattle.

What could be the issue here? I don't want to spend money on the new modem/router if the issue could be with something else. What diagnostics should I run to identify the cause of the latency? (Win10 PC).

Solution 1:

maybe the DNS you are using, when not on VPN, is slow.

How did you measure your latency?

one quick way to test it is to ping a URL and then its equivalent IP address like:

ping google.com
ping 172.217.169.14

Ping time should be almost the same for both otherwise your DNS is slow.

Mind that 172.217.169.14 is a European server, you should find a google IP from Australia by querying your DNS. In Linux you do it with "dig google.com"