VTP pruning in transparent mode

aueddonline

Bit confused about this, The book suggests that you can manually prun when in VTP transparent mode, does that mean that if you prun a vlan on a trunk and the downstream switch has an access port for that vlan, that vlan traffic won't get to the downstream switch?

I did lap this up and the vlan traffic seemed to still move across the trunk but how could it, if the switches are not sharing information via VTP?

APA

Pruning only takes affect if the downstream switch does not have a switchport assigned to the vlan you are attempting to prune.

The minute the downstream switch applies this vlan to a switchport all pruning goes out the window as then asyou said the traffic would be prevented from getting to the switch.

As soon as the vlan is removed from the downstream switch then pruning takes affect again.....

Think of what pruning does....

- It limits the scope of vlan traffic (broadcasts, flooding due to unknown mac etc)
- If a downstream switch had a switchport assigned to a vlan it needs to recieve this traffic as it is part of the logical VLAN topology
- Once the downstream switch doesn't utilize that vlan on a switchport then pruning can function as intended and prevent this switch from receiving unnecessary traffic.

However if you start talking about trunk security.... and you remove the vlan from the trunk with 'switchport trunk allowed vlan'

Then all traffic associated with the VLAN will fail to get to the downstream switch as the VLAN would not be allowed to traverse the trunk.

Hope this helps

aueddonline

A.P.A wrote: »

Pruning only takes affect if the downstream switch does not have a switchport assigned to the vlan you are attempting to prune.

The minute the downstream switch applies this vlan to a switchport all pruning goes out the window as then asyou said the traffic would be prevented from getting to the switch.

As soon as the vlan is removed from the downstream switch then pruning takes affect again.....

Think of what pruning does....

- It limits the scope of vlan traffic (broadcasts, flooding due to unknown mac etc)
- If a downstream switch had a switchport assigned to a vlan it needs to recieve this traffic as it is part of the logical VLAN topology
- Once the downstream switch doesn't utilize that vlan on a switchport then pruning can function as intended and prevent this switch from receiving unnecessary traffic.

However if you start talking about trunk security.... and you remove the vlan from the trunk with 'switchport trunk allowed vlan'

Then all traffic associated with the VLAN will fail to get to the downstream switch as the VLAN would not be allowed to traverse the trunk.

Hope this helps

switchport trunk allowed, that's what I was missing I was changing the elgbility