VTP pruning , A question

[sinaastane]

hi

There is a switch with vtp pruning enabled,and this switch does not have any access port on vlan 4,except an ip address and mask that is assigned to vlan 4 interface.

My question is:

does vtp pruning can cause this switch not accesible through an ip address set on vlan 4 on this switch?

could anybody answer me. thanks.

[Dennis Mink]

attach the config of both switches please

[sinaastane]

Hi dennis.

unfortunately  i dont have access to those switches at the moment. so i cant check trunk pruning vlans.

i'm sure that all other vtp settings are correct. and default GW set correctly

does vtp pruning can have such an effect at all?

[paul driver · Accepted solution]

Hello

With Vtp pruning enabled  Switch(s) send vlan membership announcements (VMA) messages between each other to notify interest in a specific vlan

If a certain switch doesn’t send this interest within these vma's then the vlan will be pruned off the trunk

My understanding is L3 ports are not applicable in this process, so the switch where this L3 port is applied will NOT request this vlan in its vma's

res

Paul

[Rolf Fischer · Accepted solution]

this switch does not have any access port on vlan 4,
except an ip address and mask that is assigned to vlan 4 interface.

Are you saying you've created a SVI for VLAN 4 on that switch (interface vlan 4)?

If so, this is a scenario you could find on a single core switch as well: No access-ports, just trunk(s) and a SVI. Wouldn't be a good idea if the switch doesn't request that vlan in its (pruning) Join messages then, I guess.

HTH
Rolf

[EDIT]:

I did a quick test with a cat2960-8 with a 'debug sw-vlan vtp pruning' enabled:

Switch(config)#do show interface g0/1 pruning
Port                Vlans pruned for lack of request by neighbor
Gi0/1               2,4

Port                Vlan traffic requested of neighbor
Gi0/1               1

Switch(config)#interface vlan 4

VTP PRUNING DEBUG: trunk Gi0/1 rx Join, len=166 (domain VTPTEST)
VTP PRUNING DEBUG: trunk Gi0/1 timeout
VTP PRUNING INFO: domain VTPTEST vlan 4 chg local assoc to 1
VTP PRUNING INFO: trunk Gi0/1 vlan 4: J0->1 (trig Join)
VTP PRUNING INFO: trunk Gi0/1 - send trig Join

Switch(config-if)#do show interface g0/1 pruning
Port                Vlans pruned for lack of request by neighbor
Gi0/1               2,4

Port                Vlan traffic requested of neighbor
Gi0/1               1,4

Please let us know if I misunderstood the question.

[sinaastane]

thank you rolf

by the way if someone issue this command "switchport access vlan 4" on that trunk , does vlan 4 still be pruned?

[Rolf Fischer]

Thanks for using the rating system.

If the port is hard-coded as 'mode trunk', the 'switchport access vlan x' command shouldn't have any impact.

But note that the pruning state can be different on both sides of a trunk. The example above shows that the switch requests VLAN 4 traffic from its neighbor, so the neighbor won't prune vlan 4 traffic on that trunk, wheres the local switch does (because the neighbor does not request VLAN 4 traffic).

HTH

Rolf