Roy, Thanks for your answer. Could you please tell me more about your proxy settings?
We have a virtual host definition like the following. Yesterday we started adding the ProxyPreserveHost, ProxyVia, ProxyPassReverseCookieDomain while chasing the session mix up issues. It is still happening although very rarely. And it is hard to reproduce on demand... This virtual host points to two RT instances. RewriteEngine on RewriteRule ^/(.*) - [P,QSA] ProxyPreserveHost ON ProxyVia Full KeepAlive On ProxyPassReverseCookieDomain mydomain.com <Proxy balancer://proxy-balancer> BalancerMember http://xxx.xxx.xxx.xx1/rt_demo BalancerMember http://xxx.xxx.xxx.xx2/rt_demo </Proxy> ProxyPass /rt_demo balancer://proxy-balancer And on each RT instance we have the 'classic' setup: Alias /rt_demo "/opt/rt3/share/html" PerlModule Apache2::compat PerlModule Apache::DBI PerlRequire /opt/rt3/bin/webmux.pl AddOutputFilterByType DEFLATE application/x-javascript text/css text/html <Location /rt/NoAuth> Order allow,deny Allow from all Satisfy any </Location> <Location /rt/REST/1.0/NoAuth> Order allow,deny Allow from all Satisfy any </Location> <Directory "/opt/rt3/share/html"> AllowOverride All Options ExecCGI FollowSymLinks AddDefaultCharset UTF-8 SetHandler perl-script PerlHandler RT::Mason </Directory> Thanks, Thierry