In httpd.conf, make sure the Apache server only listens to port 80 on the localhost interface:
Listen 127.0.0.1:80
If using Touchstone, then also add the following to the end of httpd.conf:
ProxyPass /Shibboleth.sso/ https://idp.mit.edu/Shibboleth.sso/ ProxyPassReverse /Shibboleth.sso/ https://idp.mit.edu/Shibboleth.sso/ ProxyPass /Touchstone/ https://idp.mit.edu/Touchstone/ ProxyPassReverse /Touchstone/ https://idp.mit.edu/Touchstone/
In squid.conf, make sure the following items are set as described:
http_port ist-prod-pubs1.mit.edu:80 defaultsite=ist.mit.edu vhost http_access allow all cache_peer 127.0.0.1 parent 80 0 no-query originserver name=Accelerator
Restart the Apache server:
/etc/init.d/web restart
If using Touchstone, then restart shibd:
/etc/init.d/shibd restart