How Do I Build a Ceph Cluster Network?

[Rolland]

Here's my hardwares:
1. 6 servers, each with 4 * 25GB NICs
2. Two 25GB switches,These two switches are only used for CEPH's cluster network.
I want to avoid a single point of failure for server NICs and switches, how do I build this cluster network?
It's two switches. Is it stacking or cascading?
What are the configuration requirements?

Many Thanks.