First, set up the server to authenticate against the portal login module. In this example, the CAS server is installed on Tomcat.
By default on logout the CAS server will display the CAS logout page with a link to return to the portal. To make the CAS server redirect to the portal page after a logout, modify the cas.war/WEB-INF/cas-servlet.xml to include the follow line :
<bean id="logoutController" class="org.jasig.cas.web.LogoutController"
p:centralAuthenticationService-ref="centralAuthenticationService"
p:logoutView="casLogoutView"
p:warnCookieGenerator-ref="warnCookieGenerator"
p:ticketGrantingTicketCookieGenerator-ref="ticketGrantingTicketCookieGenerator"
p:followServiceRedirects="true"/>