We prune the VLANS manually and our Core switches are running in Hybrid mode so we execute the CAT OS commands. The Set trunk command and the clear commands.

As with Amit's post if you enable VTP pruning on a VTP server then it is enabled throughout the VTP domain. The clear and set commands are used to toggle between a vlan being prune eligible or prune ineligible but you still need to enable VTP pruning on the VTP server.

You can however clear vlans off a trunk on a port by port base - this stops traffic for that vlan going across the trunk. Is this what you mean ?

Jon

Its suggested to do it on both the sides. If you do it on one side only, the other side will still be sending the unncessary STP BPDU's and other L2 related traffic on the trunk links and will be wasting unncessary bandwidth.

BUT if it is unneccessary bandwidth is the only reason for doing it how much bandwidth is it using. I do not see that as a huge downfall considering we are using 2Gig for our uplinks. So is there other reasons aside from bandwidth?

By doing this would it cut down on STP instances? I have an issue with a device saying it exceeded the maximum platform limit of 128 STP instances.

Clearing vlans off trunks will stop STP for that vlan going across the trunk. So if you have a switch which has reached the limit then clear vlans off the trunk to that switch until you are below 128 - as long as you don't need > 128.

The other alternative is to use VTP transparent where you have very precise control over which vlans exist on the switch.

Jon