A typical Collapsed Core (Layer 2 Access) LAN is shown below as an example. Here two core switches are used. Each Core does not typically require dual Supervisors unless high availability is of utmost importance. Each edge switch is connected to each Core switch by an individual trunks or EtherChannel. The Core switches are connected via an EtherChannel. This design can act as a Distribution Block for a larger design with a separate Core where the scale or layout (e.g. separate buildings) dictates a 3 tier design, with a separate Core, is used.
Loops have been introduced for resilience. To minimise the chance of an STP issues the following are configured:-
Core switches are configured for STP Root and HSRP (Odd and Even VLANs on alternate switches). Core switches perform inter-VLAN routing. Trunks are pruned of unnecessary VLANS.