Web Access needs to be running on both the masters and agents for it to function correctly. However we only support logging in on the master machines. But we don't have anything properly enforcing that, so a user might connect directly to an agent and get a login form. As long as the vsmserver service is off then the login will fail, but it is not apparent to the user that they are using the wrong address.
It's worth noting that by default, in a cluster setup, the button "Back to login page" that's shown in Web Access after disconnecting or logging out will send you to the wrong login page. The user will in this case end up on the agent server, and not on the master. By setting the config parameter /webaccess/login_page the admin can fix this, however, this isn't mentioned in our chapter about setting up a ThinLinc cluster. It's only mentioned in the Web Access chapter.
(In reply to Samuel Mannehed from comment #2) > By setting the config parameter /webaccess/login_page the admin can fix > this, however, this isn't mentioned in our chapter about setting up a > ThinLinc cluster. It's only mentioned in the Web Access chapter. This was split to bug 7882.