Varnish 3 serving same set of pages for different domains

[Mark E]

Hi,

I have a strange issue that I need some help with. Here's the server 
config:

- CentOS

- Varnish 3 on port 80 installed in front of Apache on port 8080

- 6 web sites exist on the server, all with individual unique domains 
and or subdomains

- All sites work fine via Apache

When I add Varnish 3, pointing it at Apache as the backend, I see the 
same site content no matter what subdomain/domain I open in a browser. 
But the URL in the browser always appears correct.

To troubleshoot this I've gone to a generic VCL with no rules at all, I 
only have the "backend" declaration to tell Varnish that Apache is on 
port 80 at x.x.x.x address - and to be clear I'm using the default.vcl 
that comes with Varnish 3 with the RedHat repository, which has no 
rules, etc., enabled.

So to summarize this is what happens:

- Enable Varnish

- Open a.com and in a browser and it works fine, I see a.com content.

- Open b.com in a browser and b.com is shown in the browser address bar, 
but the content I see is from a.com.

- Disable Varnish, put Apache back on port 80, and both a.com and b.com 
load properly in a browser - I see the correct content for each site.

Any ideas why this happens?

Mark