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We've got a server on our network and some drives on that server mapped to our desktops. When I transfer a file over, windows task manager reports 100% network utilization on local area network, which is great.

How can I check whether this consumes internet bandwidth or not?

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up vote 7 down vote accepted

You can disconnect your Internet, and should find that it still works fine, unless there is some strange reason the server relies on the Internet.

Depending on your router, it could slow down the network, including Internet access, for other users, but will not affect the Internet connection.

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Yes, that "strange reason" is what I am concerned about. Took some time to figure out how to disable my internet connection while staying on the network, but I managed to cut off internet and could still transfer files over. So it's probably ok. – MxyL Mar 24 '14 at 20:27
You can use a tool like Wireshark to look at all traffic from the computer if you want to see what is being sent where. – Nattgew Mar 24 '14 at 20:28

Short answer is no it should not.

Local network usage does not constitute internet usage, so just disconnect your cable / adsl line and test. It should still be pumping the data at full capacity, but it should not be using the net for it.

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Tested, doesn't need an internet connection! – MxyL Mar 24 '14 at 20:28
VPNs can hide whether it actually goes over the internet. – David Ehrmann Mar 25 '14 at 1:23

The short answer is that no it should not because packets sent from your computer to a server on the same local network should never leave the local network assuming the network is sensibly configured.

However, the short answer makes another assumption about your network, which is that your local network is actually local. Many organisations now outsource services to the cloud and use various technologies to tunnel data packets across network boundaries (e.g. over the public Internet) while making it all look like the server has a local IP address.

Alternatively, the server could be in your network but at another location, such as a remote data centre or another office, which would similarly require packets to tunnel across the public network (Internet).

The upshot is that large file you're transferring to a file server on your network could actually be chewing up Internet bandwidth. The only way to know for sure is to ask someone who understands your network topology and knows for sure where the server is both physically and logically.

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The server box is located in a room right behind us, so it should be fine I think! – MxyL Mar 25 '14 at 15:40
There goes that "should" word again... – Marky Mark Mar 26 '14 at 3:31

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