What happens if I change the DNS of system

Question

I am using internet using Huawei USB Data Card. It has an option of Mobile broadband. and when I connect through mobile broadband I noticed that I can change the IPv4 DNS address.

What will happen if I change the DNS server address? I mean speed gets affected or not. If it speed is affected then at what extent it will be.

Answer 1

The choice of DNS servers does not really affect connection speed. If your connection is slow, it will remain slow. Only thing is, it might identify hosts faster, but the difference will be a fraction of a second. What a different choice can do is to circumvent censorship. Serious DNS servers (OpenDNS, Google...) do not apply any censorship, but this is not true for every DNS server, and most definitely not true for those favored by some ISPs.

In any case, there is a simple application that allows you to check on both DNS server speeds, and their inclination to apply censorship: it is called namebench, and is provided, free of charge, by Google. It works on Windows, Unix (including Mac) and Linux. You may want to give it a try.

Answer 2

You'd use a different DNS server. Assuming its a valid dns server it will affect dns lookups. Since your system caches these, it'll make a difference only when you make a fresh DNS lookup. While it'll make a VERY small difference - in some cases its nice if your ISP has unreliable DNS servers.

If its an invalid server address... well, anything that uses DNS breaks.

Practically speaking, unless you experience issues there should be no need to change this.