Vanity URLs redirect analytics

[JS_Bournival]

I do not know if this is possible, but if a vanity URL is set on a page, and the redirect option is enabled:

mysite.com/vanity -> 301 -> mysite.com/deep/link/to/page.html

How can I track, for analytics purposes, in this page, that the original request was made for the vanity URL ?

Is there something in the HTTP request that is supposed to express that? Or once the redirect happens, I lost all trace that the user used the vanity?

Thanks a lot.

JS.

[JS_Bournival]

On a sidenote: I just noticed vanity URLs aren't using 301, but 302 instead ...