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In PuTTY, you have to add/select your private key to Connection → SSH → Auth to be able to log in. In PuTTY version 0.78 this option has changed to Connection → SSH → Auth → Credentials.
Internal Login
SSH for internal connections between nodes of Lise works right out of the box - that is, without specifying any keys. This is enabled through host-based authentication which is active by default.
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