How sharepoint understand when user requests for web applications by their DNS names

Question

HI
I configured Alternate access mapping in my sharepoint farm for default ,intranet zones
and spt farm has two web front end servers and they load balancing by F5 device
in WFE servers there are different web applications are running on different ports
so here I want to know how load balancing works, load balancing configured in F5 device.
when users request a webapplication from browser (ex http://cms) where this request will go
1)when I ping cms and other web applicaations  it returns me a loadbalancer  server IP  for all web applications;
ping cms : it returns 10.xxx.0.80 , same ip returns when I ping for other web app
but ex CMS web application run on the 10.xxx.1.26:81 port in sharepoint server
2) and these sharepoint web applications running on different ports in sharepoint  web servers , so here  how sharepoint understand when user requests for web applications by their DNS names
http://cms and http://products  etc
adil

Answer 1

I'm not sure if the F5 can add a port number (I'm not an expert on load balancers).  But in general if you design the SharePoint site to run on port 81 then you need to have port 81 appended to the request or it won't work.  http://cms in your
example would take you to http://cms:80 not http://cms:81.  But in general DNS will resolve the address back to the F5 load balancer.  The load balancer will look at the header of the HTTP request (which contains the original address you requested)
and forward the request to the appropriate web front end IP address.  If your web front end is using one IP address for multiple sites then those sites need to be differntiated by using a custom port like 81 (which must be included in the original request)
or because a host header was bound to the web application when it was created.  If they are running on different port numbers then the request must include the port number by the time it gets to the SharePoint server.
Paul Stork SharePoint Server MVP
Principal Architect: Blue Chip Consulting Group
Blog: http://dontpapanic.com/blog
Twitter: Follow @pstork
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