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Open a web browser and go to https://vpn.slac.stanford.edu/ , logon with your SLAC's windows credentials. Username must NOT be prefixed with "SLAC\". Then click on "Start AnyConnect". The VPN client will be installed/upgraded if necessary before connecting you (this is working on Windows, linux and MAC OS).
On a SLAC built windows device the vpn client is pre-installed, so you can just go on start menu -> launch Cisco Anyconnect Secure mobility client. Then ensure the connection string is "vpn.slac.stanford.edu" and click on connect. Enter your SLAC's windows credentials, accept the banner and you are connected.
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