How to do a Forms Authentication across Sub-Domains

Is it possible to authenticate users across sub-domains when the authentication takes place at a sub-domain instead of the parent domain?

For example:

User logs into, and then we need to send them to

Can I authenticate them to the reporting site even though the log-in occured at a sub-domain?

Jason from Washington DC

One thought on “How to do a Forms Authentication across Sub-Domains

  1. Hello Jason

    You can set an authentication cookie to be the parent domain at authentication time but you have to explicitly set it, and it will default to the full domain that you are on.

    Once the authentication cookie is correctly set to the parent domain, then all sub-domains should be able to read it.

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