In a point-to-point topology, each router needs a single security zone, a single Tx-SC for encryption, and a single Rx-SC for decryption. Each SC has two SAs. In total, for point-to-point topology, four SAs are needed: two Rx-SAs for Rx-SC1 and two Tx-SAs for Tx-SC1.
The following figure shows the P2P topology.
Figure: P2P (switch-to-switch) topology
