security - Jenkins login fails to complete -

i working systems behind corporate firewall.

jenkins installed in google cloud server , had external ip of server, open access in google cloud firewall rules.

recently change request came corporate security team, had block public/external ip access jenkins. vpn allows me connect jenkins on internal ip.

since able open jenkins console-login page...but after submit credentials, login of jenkins failing complete... forcing me use rdp remote jenkins server access jenkins console.

the login form gets submitted/redirected "/j_acegi_security_check" url. responds "net::err_connection_aborted"

any pointer appreciated, fix issue.