The core switches provide high performance backbone routing between the edge, aggregation, data center, and external Internet networks.
An additional high availability backbone ring is built that combines EAPS and OSPF. Using EAPS and OSPF together increases the stability of IP routing tables. Since EAPS provides 50-millisecond convergence for link failures, OSPF adjacencies do not flap. In this example, the backbone ring is formed by adding two core L2/L3 switches and connecting them to the two existing aggregation switches. The core switches also provide routing to the Internet using BGP (see Core EAPS and OSPF Network Layer).
Using redundant core switches protects against a single point of failure at the switch level. OSPF provides fast convergence from any routing failures. EAPS provides the resilient L2 foundation and minimizes the occurrence of routing interface flaps or dropped OSPF neighbor adjacencies. Combining EAPS and OSPF provides the highest level of network resiliency and routing stability.
Configuring the core switches requires a new EAPS domain with a single EAPS protected VLAN with OSPF forming the backbone IP network. Additional configuration is needed on the aggregation switches to connect them to the backbone EAPS and OSPF ring. Since the steps are similar to previous configuration examples, the L2 (EAPS) and L3 (OSPF) configurations are combined. Since the BGP configuration is independent of EAPS configuration, BGP configuration is not discussed here.
To configure backbone connectivity on the core and aggregation switches, complete the tasks described in the following sections: