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.
I more go on the big approach - unplug a server and on the next try storage and on the last one a switch - or in any other order - if the system survives that -> all good. But if you do have a lot of time (and someone to pay for it), you can try each small problem on it's own...

Tsg