After sign-in , sharepoint redirect to unexistent page /_trust/default.aspx
[execute][Response status code from backend webserver is 500]
from Windows Event Viewer.
Exception message: ID3206: A SignInResponse message may only redirect within the current web application:
'http://server1.domain.com:8080/sites/Vendas/_layouts/15/Authenticate.aspx?Source=[%]2Fsites[%]2FVendas' is not allowed.
SiteMinder Agent for SharePoint, Version 12.52, Label 142
Policy Server Version (12.52; Update: 01.02; Build: 766; CR: 02)
O.S : SunOS 5.10
Problem could be due how the site is being accessed in the browser without the trailing "/" or possibly the ProxyRules.xml is missing the "$0" in the FORWARD statement.
1. 1. Configure a root site collection in Sharepoint.
2. Configure the Sharepoint to authenticate with the Agent.
Reference : how to create a root Site Collection on Sharepoint