External authentication on a different system than the IdP

[Brian Reindel]

Is it possible to have the external authentication live outside the
context of the IdP? I noticed the externalAuthnPath is context
relative. Basically we have a login page already configured for our
external authentication system, but it it isn't on the same server as
the identity provider. Will this not work given how external
authentication is configured, or am I misunderstanding the
capabilities?