Internal and External vulnerability scans

I understand the description of internal and external vulnerability scanning but I'm a bit confused.
An external scan would examine your firewalls/routers etc. Devices that connect to the internet
An internal scan would examine devices inside a network that don't have internet connectivity. I can't think of anything inside a network that doesn't have internet connectivity. What devices should I be considering for an internal scan?
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External scans look at machines that are accessible from the Internet at large.  Web servers, mail servers, firewalls, etc.

Internal scans basically look at all machines and devices on your network, from inside of your firewall.

Internal scans usually require an appliance on site.  External scans can be done remotely.
Internal scans target devices/hosts can are not accessible FROM the Internet.

" I can't think of anything inside a network that doesn't have internet connectivity."

Correct, but there are two types of "Internet" connectivity.  Outbound, that is the device/host accessing something in the Internet.  Inbound, that is something/someone accessing the device FROM the Internet.

You may have a server that can get to the Internet to download patches for example.  However, I may not be able to access that server from the Internet.

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DonKwizoteAuthor Commented:
Thanks Guys.
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