Question: I have **Cisco Catalyst 2960-s** switch and I want to configure *three Vlans* (A; B; C)

I want to : 

* *Allow* traffic between A and B
* *Allow* traffic between A and C
* *Block* traffic between C and B

or if there is other method to permit/deny access between switch ports.

Answer: 
**- Power off a host.** - To test high-availability and admission control.

**- Power off a switch.** - To test failover links.

**- Disconnect data and storage network cables independently.** - To test resiliency, load balancing and datastore heartbeat/host isolation state. Also storage controller failover.
When we test failure scenarios we start by removing individual wires/fibres, then whole NICs/HBAs, then servers, then switches - i.e. small to large - simply because if the platform can't handle the small then testing on the large will be pointless.

That said I can't see any issues with your setup, not as you've explained it anyway.