- A virtual community of network engineers
 Home  BookStore  StudyNotes  Links  Archives  StudyRooms  HelpWanted  Discounts  Login
Re: trunk allowed vs pruning posted 08/12/2006
[Chronological Index] [Thread Index] [Top] [Date Prev][Date Next] [Thread Prev][Thread Next]



Except I am missing something, I do not see how VTP pruning will always solve the second problem, to my understanding the second problem states that:


>traffic for vlan 8 should not be received over any of the other trunk 
> links


When VTP pruning is enable on a switch, the switch is simply saying, "....I will not receive VLAN traffics through any trunk interface for any pruning eligible VLANs that are not locally assigned". 


For pruning eligible VLANs, VTP pruning dynamically turned ON or OFF the reception of specific VLAN traffics depending on the existence of that VLAN in the receiving switch.


The only time when VTP pruning will be sufficient for the above task is when VLAN 8 is not locally assigned/configured on SW1.And if VLAN 8 is not configured on SW1 today, the mention of VLAN 8 might be a prelude to its addition in the future and one will want his/her solution to also address that situation.


It is very important that one's understanding & application of these technologies is not limited to how it is applied in a particular vendor's workbook. How one interprets Words like NOT, NEVER, MAY, ALWAYS, etc goes a long way in determining the out come of the Lab exam.


Since VTP Pruning is a dynamic process which rely on the existence of a locally assigned VLAN, it might not be a good idea to depend on it as a solution for a task that states that a particular VLAN should NOT be received over a trunk port.  


It is always good to nail down one's solutions, do not leave anything to chances. More so because one do not know how the proctor will test to see if a particular task was given the appropriate solution. e.g. One valid proctor test for the above task might be to configured VLAN 8 on SW1; if that is the case, then only enabling VTP pruning and not editing the VLAN Allowed list might not be the correct solution.




Godswill Oletu
CCIE #16464

  ----- Original Message ----- 
  From: kwasi-ccie@xxxxxxxxxxx 
  To: Godswill Oletu ; Tim Chan ; ccielab@xxxxxxxxxxxxxx 
  Sent: Friday, August 11, 2006 1:42 PM
  Subject: Re: trunk allowed vs pruning

  You only need to remove vlan 8 from the prune eligible list on sw1 port fa0/13 to solve problem 1 (switchport trunk pruning vlan remove 8).  Problem 2 is already solved by the vtp pruning that you enbaled on both switches.  You do not need to play with the vtp allowed list to solve these 2 problems.  Test it out.

    -------------- Original message -------------- 
    From: Godswill Oletu <oletu@xxxxxxxx> 

    > Tim, 
    > The solution you provided will only take care of the first task, once VLAN 8 
    > is removed from the prunning eligible list of interface fa0/13, the switch 
    > will continue to receive traffic for VLAN 8 regardless of local assignment 
    > or not. 
    > For the second task, you have to remove VLAN 8 from the VLAN allowed list on 
    > interfaces fa0/14 & fa0/15. 
    > HTH 
    > Godswill Oletu 
    > CCIE #16464 
    > ----- Original Message ----- 
    > From: "Tim Chan" 
    > To: 
    > Sent: Friday, August 11, 2006 2:21 AM 
    > Subject: trunk allowed vs pruning 
    > > Hi all, 
    > > 
    > > I keep confusing myself and need some clarification. 
    > > 
    > > What's the relationship between "vtp pruning" and "switchport trunk 
    > allowed"? 
    > > 
    > > In one of the workbook labs, one of the tasks states: 
    > > 1. although it does not have it locally assigned ensure that SW1 receives 
    > traffic for vlan 8 over Fast0/13 
    > > 2. traffic for vlan 8 should not be received over any of the other trunk 
    > links. 
    > > 
    > > (The two switches are trunked together on Fast0/13-15 using dot1q.) 
    > > 
    > > So my thinking is to do "switchport trunk allowed vlan 8" on fast0/13 and 
    > to not allow it on 14 & 15. 
    > > 
    > > But the solution says the answer is "switchport trunk pruning vlan 
    > 2-7,9-1001". 
    > > 
    > > How does this solution solve either of the two tasks? 
    > > 
    > > Please advise, 
    > > -tim 
    > > 
    &g t; > _______________________________________________________________________ 
    > > Subscription information may be found at: 
    > > 
    > _______________________________________________________________________ 
    > Subscription information may be found at: