In addition to 1:1 MC-IPsec, the system also supports N:M multi-chassis IPsec stateful redundancy. The term N:M is used to refer to the feature. N:M provides additional redundancy and potential cost saving compared to 1:1 MC-IPsec.
N:M allows overall N active nodes and tunnel-groups to be backup by M standby node and tunnel-group. The number represented by N can be larger than, equal to, or smaller than number represented by M.
The following graphic shows a typical N:M configuration.
Figure: N active nodes backup by M standby nodes
