why on xyz site you can configure redirect link going to sharepoint site directly? Referer header should come to F5 VIP for linkit. You can see by logging in the iRule if that comes and forward it using below iRule
when HTTP_REQUEST {
if {[HTTP::header exists Referer] }{
log local0. "referer header found"
set referer [HTTP::header value Referer]
HTTP::respond 301 Location "https://sharepoint.aspx"
HTTP::heder insert "Referer" $referer
} else {
log local0. "no referer header found"
HTTP::respond 301 Location "https://sharepoint.aspx"
#HTTP::heder insert "Referer" no-referer-found
}
}