With the Application Request Routing service becoming more widely used it was felt that it would be good to touch on how this can be used as a reverse proxy for Office Web App deployments. (this does not cover how to install the ARR software on the server or configuration for external sharepoint use).
1. To start open IIS
2. The first step is we need to add your web app servers to the configuration. So go to "Server Farms", right click and select "Create Server Farm"
a. Server Farm Name should be a friendly name or a name that allows you to differentiate between your web apps servers and lync servers or sharepoint servers
b. Server addresses should be the FQDN
c. the end result resembling below.
3. Once added to the server farms the next stage is to configure your url routing. This is the portion that looks at the traffic coming in and routes specific types of traffic to different servers i.e. separating sharepoint traffic from office web apps traffic
a. Select the root location from the navigation pane in IIS
b. now select "url rewrite"
1. you will see a rule has been created for the server you added doubleclick that rule and it will take you to "edit inbound rule"
2. Requested URL should be "matches the pattern" Using should be changed to "Regular Expression" and the Pattern should be the following (.*) Ignore case should be checked
3. We need to now add a condition.
a. Input should be {http_host}
b. Type should be Matches the pattern
c. Pattern should be as follows ^prefixofexternalurl\.domainofexternalurl\.com$ an example being ^share\.contoso\.com$ (this is what tells the ARR to reroute this specific traffic when it's sent)
Once all of the above is done you should be able to run an IIS reset and test. Again the above is only the ARR configuration settings. Your external users will not work unless you've configured the sharepoint wopi zones correctly and routed public traffic via public dns to this servers public IP address. A good way to test to verify that you have everything configured correctly for your office web apps would be to have an external resource attempt to access your externalurl for office web apps hosting discovery i.e. share.contoso.com/hosting/discovery. If you're able to see an xml page then everything should be configured correctly.
