Here is some additional information on how the content routing function works in ConfigMgr 2012. If you use this feature make sure you document the routes that have been added/deleted.
Assume there is a CM2012 SP1 primary site (BLB) with two CM2012 SP1 secondary sites (SE1 and SE2). By default CM creates file replication routes from BLB to SE1 and vice versa and from BLB to SE2 and vice versa. We used to call these file replication routes “senders”.
Assume BLB is in Dallas, SE1 is in Houston and SE2 is in College Station and the College Station network goes to Houston and then from Houston back to Dallas. Again, if the network for both remote sites went straight back to Dallas then using content routing between the secondary sites may not make sense as it would add additional traffic, latency, etc.
To adjust the file replication routes to match this scenario, we need to create routes between the two secondary sites and then remove the file replication routes between SE2 and BLB. Make sure the computers accounts for the two secondary sites can communicate with each other and do not modify the database replication links.
Now when you distribute applications to the SE2 distribution point the primary site will use the SE1 secondary to route the content to the SE2 DP. You should be able to see this routing logic in the scheduler log on the primary site. In this example I am assuming the SE1 DP should not be a DP for this content so it was not included as a targeted DP. If I was deploying content to multiple secondary sites thru the SE1 secondary the logic would be same.