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Npcap extremely slowing down connectivity at boot WIN10 #1502

crankedguy opened this Issue Mar 5, 2019 · 3 comments


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crankedguy commented Mar 5, 2019


at least in latest Windows 10 version with all patches applied npcap extremely, really extremely slows down connectivity at startup. I would not bother if we were talking about 5 seconds here, but I have to wait like 40-50 seconds on boot to get network connectivity as soon as npcap is installed.
It is not system specific, it is the same on my laptop with wireless as on my desktop with just Ethernet.
Installed :
driver not started at boot time...I don't want that
and for the rest it makes absolutely no difference if
loopback yes/no,
compatibility mode yes/no,
admin restriction yes/no
it is just always the same, tried on 2 computers as said.
Waiting a minute is too much.

Any ideas here on what that could be or how to investigate? As said I don't think it makes sense to investigate too deeply for a specific system computer problem



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dmiller-nmap commented Mar 5, 2019

We have had lots of problems getting the "driver not started at boot time" feature to work. The general issue is that Windows expects network drivers to be available at boot. If you mark your driver as "optional," then it hangs around for a while trying to see if it will start anyway. If it's "mandatory," then it's started at boot or you don't boot. I will still look into this, but be aware that it's a known source of problems.

Can you help us diagnose by providing a bit more information?

  • What version of Npcap are you using?
  • Output from DiagReport.
  • Why is it important to you to not start Npcap at boot? If it is for performance reasons, can you provide performance measurements showing that it causes slowness?

@dmiller-nmap dmiller-nmap added the Npcap label Mar 5, 2019


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crankedguy commented Mar 7, 2019

I am using npcap-0.99-r9
Well are we just talking now about just a driver load with this setting or the running service in terms of packet capturing possibility? Because I don't care if a driver is loaded at boot but I do care if a capturing service is started/running at boot. That is why I disabled this. Don't want that on my machine(s) and with Winpcap it was always done manually without issues and without delays on boot. When I want to capture packets it is no issue to do a simple net start command, and that is how it should be from my pov.
I will be away for some time now so I might not answer shortly but will stay on this topic.



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gvanem commented Mar 7, 2019

... and with Winpcap it was always done manually without issues and without delays on boot.

Speaking for myself, I have no need for NPcap until such trivia is fixed.
But what features of NPcap do you really need in favour of WinPcap now?

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