Start IBM HttpServer

Go under the bin dir of default installation, on AIX:

cd /opt/IBM/HTTPServer/bin


stop:
./apachectl -k stop


start:
./apachectl -k start -f /opt/IBM/HTTPServer/conf/httpd.conf


The WebSphere plugin file (plugin-cfg.xml) allows to link the IBM HttpServer as webserver of Websphere that starts with the command above.
If the http requests are not served by http server on the port 80 and not forwarded to the related the application server ports (9080, 9081.. depending how big is the cluster), check  if the plugin file is correctly  defined with actual ports and hosts of the application servers currently running. The WebSphere plugin file is located for example here:

/opt/IBM/WebSphere/AppServer/profiles/PROFILENAME/config/cells/HOSTCELLNAME/nodes/HOSTNODENAME/servers/webserver1/plugin-cfg.xml

If needed you can regenerate and propagate the plugin from was admin console (Server -> Server Type - Web servers):