Devices in the same vlan cannot communicate

[ysu]

I have a 2960X 24 ports switch, ports 1-12 are divided to vlan41, ports 13-20 are vlan42. PC1 is in vlan41, PC2 and PC3 are in vlan42. PC2 and PC3 are both able to communicate with PC1, but PC2 cannot communicate with PC3. If plug PC2 and PC3 into ports in vlan41 then all three PCs can communicate with each other. If plug all three PCs into vlan42, all of them cannot communicate with each other.
In short, the issue is that PCs in vlan42 cannot communicate with each other, when trying to ping, it returns "Destination host unreachable", but PCs in vlan42 can communicate with PCs in vlan41 correctly.

[MHM Cisco World]

Friend two host connect to same SW and SW port assign to same VLAN.
there is no OS FW stop ping 
there is easy first step, even if it in same VLAN did you check IP in PC ? are it in same subnet ? if not it can not ping to each other

MHM

[ysu]

Yes, it's in the same subnet. When I moving these two PC to another switch they can communicate correctly, so there should be something wrong with the switch or switch configuration.

[MHM Cisco World]

Show vlan brief 

Check if vlan you test is shut<-

MHM

[ysu]

Their status is active and "show interface gi/10/13(16)" indicates both 13 and 16 are up and connected. 

[andrewswanson]

Dos the output of "show vlan" show both vlans 41 and 42 as being present on the 2960?

hth

Andy

[ysu]

Yes, they are present and status are active.