3.5.b Implement and troubleshoot neighbor relationship

3.5.b [iv] OTP multiple service providers scenario

The EIGRP OTP solution simplifies multi-provider IP WAN network designs. It simplifies the interface with the WAN providers and facilitates an end-to-end EIGRP network, which is easier to troubleshoot.

EIGRP OTP is configured in the Customer Edge (CE) routers. They include CE, CE1 and CE2. CE1 and CE2 establish an EIGRP neighbor association with CE, which maintains a database of all the Customer Edge routers and their associated prefixes. Essentially, the router CE is supporting a route reflector type functionality for EIGRP. This is accomplished with a single line of configuration on the each router. Once the EIGRP neighbor association is established the customer’s traffic or data forwarding can start.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 3085-3091).  . Kindle Edition.

http://blogs.cisco.com/getyourbuildon/simplifying-multi-provider-wan-designs/