Effects of enbling VTP prunning.

[kashyap1977]

i have one core switch (cat6509) and some access switches (cat4006) connected via fibre.

In my cat6509 we have 2 MSFC module, it went automatically on secondary MSFC.

I have made some observation, and we got lots of broadcast & multicast traffic.And i got a suggesstion to enable ENABLE VTP PRUNNING in my entire management domain, which is disable by default.

so i just want to know what will be the effect on my network if i enable it.

And how should i know whether all devices on my network supports VTP Prunning or not.

kindly suggest.

cheers

kashyap

[Prashanth Krishnappa]

It will eliminate not required VLANs over a trunk. If I were you, I would manually clear off the not required VLANs on the trunk versus using Pruning

[sachin]

If you have multiple VLANs in your network , only then pruning is going to help you. If you have configured Dynamic VLANs then enabling pruning is preferred over manually clearing VLANs on trunk links. I dont think manually clearing VLANs is good over enabling pruning as enabling pruing will take care of elimination of VLANs on trunk links automatically.So i will prefer something which is automatic rather manual.

[kashyap1977]

hi

we have not any of the unrequired Vlan.if i enable prunning, what kind of an impact it will have on my network.

what will be the advantages of enabling it, if all of my access switches are connected via core switch.

kindly suggest.

cheers

kashyap

[milan.kulik]

Hi,

the effect is following:

With VTP pruning enabled, user broadcasts are not sent to the trunk if there are no users connected to the neighbour switch in the particular VLAN.

Example: User x is connected to switch A in VLAN3. There is a trunk to switch B. There is no user connected to switch B in VLAN3. User x sends a broadcast. Without VTP pruning enabled, this broadcast would be sent through the trunk to switch B. With VTP pruning enabled, the broadcast is not sent to the trunk.

But STP BPDUs are still sent on the trunk for VLAN3.

When disabling VLAN3 on the trunk manually, neither STP BPDUs nor user data are sent to the trunk.

See VTP pruning section in

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_6_2/confg_gd/vtp.pdf

for details.

Regards,

Milan