What?

Though the default gateway is set successfully and it does report you the correct configuration when you run ipconfig /all command. You tend to loose it or finds missing after the computer restarts

Why?

If you double-click the following registry entry, you find that a null character exists in the value data of the DefaultGateway subkey:

Note <GUID> is the interface value of the network card.

How?

I found 2 ways that would usually fix the issue, based on your expertise you can choose either of the solution.

Fix 1

• So, after you figure out your interface and Open the value “DefaultGateway” by double clicking it. You will see a list of all the gateways that disappeared! (based on how long you are trying to fix the issue and how many gateways you tried to use, you could see one or many) Very likely, the first line will be empty. Manually remove this first empty line, click OK and a reboot should fix the issue.

Fix 2

• Resetting TCP/IP will fix the issue, to do this, simply use
  • netsh int ip reset
• if you need a log on what all changes did the command do, you can use
  • netsh int ip reset c:\resetlog.txt

Gotchas & Additional Info:

• Sometimes, a log file is not getting created while using the command netsh, right now, I am not sure why it happens.
• more info on netsh can be found at link
• more info on the registry settings that was detailed in the first step can be found at this link