tcpdump info shows the first call from the client, and then the redirect call....
edit
...but...
I tried with an apache box as the target, and noticed that the host and uri is getting changed but the content is still coming from the original (iis) servers
(b.domain.com is apache server)
HTTP/1.1 301 Moved Permanently
Content-Type: text/html; charset=UTF-8
Location:
http://b.domain.com/test.txt/
Server: Microsoft-IIS/7.5
X-Powered-By: ASP.NET
Date: Thu, 12 Jan 2012 21:43:40 GMT
Content-Length: 156
Document Moved
test.txt does not exist on s.domain.com but does on b.domain.com, which explains the appended trailing slash I see - the iis boxes rewrite the 404 page.
But I want to load the content from the other server whether it exists in the first domain or not.