How shibboleth idp verify existing session.

[Cantor, Scott]

> 1.User hits application via sp1 ,user asked for authentication and idp
> session is created.
> 2.User next hits the application via sp2 and is redirected to idp login
> page .

The only IdP login page that exists is part of the Password login flow, so that's simply not possible unless you're being very imprecise in what you're asking about.

> Am I missing out something in External authentication or is it designed that way ?

External is identical to everything else, SSO is automatic if the request can be satisfied with the old result.

-- Scott