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VTP Pruning - posted 06/25/2003
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i have a question about vtp pruning on 3550s.  I have 2 switches:

 

3550-1

F3/5  vlan56

F3/23-24 Port Channeling to 3550-2

 

3550-2

F0/4  vlan4

F0/6  trunking vlan56,76

F0/7  vlan76

F0/8  vlan8

F0/9  vlan9

F0/23-24 Port Channeling to 3550-1

 

VTP pruning is enabled on both switches.  3550-1 has no ports in vlan 4,8,9
but when i do a 'sh vlan' on 3550-1, the vlans are being listed:

 

3550-1>sh vlan

VLAN Name                             Status    Ports

---------------------------------------------------------

1    default                          active    Fa3/6

4    VLAN0004                         active    

8    VLAN0008                         active    

9    VLAN0009                         active    

56   VLAN0056                         active    Fa3/5

76   VLAN0076                         active    

1002 fddi-default                     active    

1003 token-ring-default               active    

1004 fddinet-default                  active    

1005 trnet-default                    active

 

Also, 'show int trunk' lists those vlans as not pruned:

3550-1#sh int trunk   

  

Port      Mode         Encapsulation  Status        Native vlan  

Po1       desirable    n-isl          trunking      1  

  

Port      Vlans allowed on trunk  

Po1       1-4094  

  

Port      Vlans allowed and active in management domain  

Po1       1,4,8-9,56,76,1002-1005  

  

Port      Vlans in spanning tree forwarding state and not pruned  

Po1       1,4,8-9,56,76,1002-1005 

 

Whereas on 3550-2, those ports are pruned:

3550-2#sh int trunk 

 

Port        Mode         Encapsulation  Status        Native vlan

Fa0/6       on           802.1q         trunking      1

Po1         desirable    n-802.1q       trunking      1

 

Port      Vlans allowed on trunk

Fa0/6       1,56,76,1002-1005

Po1         1-4094

 

Port        Vlans allowed and active in management domain

Fa0/6       1,56,76

Po1         1,4,8-9,56,76

 

Port        Vlans in spanning tree forwarding state and not pruned

Fa0/6       1,56,76

Po1         1,56

 

Is this normal operation?  My understanding of VTP pruning is that traffic
on ports that are prune eligible, would not be transmitted across the trunk
to a switch that has no ports in that vlan.