VTP prunning

DevilWAH

OK so i understand pruning and how it works and all. But is there any way to see it working ?

I have 3 switches connected in a ring,

SW1, SW2 and SW3.

they are all in the same VTP domain and that's working fine.

I set up VLAN 300 on one of the switches and this was replicated to all other switches.

I then turned on VTP pruning. and set up two of the switchs to have a vlan interface in vlan 300 with a ip-address (I assume this counts as a port assigned to a vlan)

but all

#sh VTP counters shows is

VTP pruning statistics:

Trunk Join Transmitted Join Received Summary advts received from
non-pruning-capable device

---

---

---

---

Fa0/22 122 122 0
Fa0/24 123 123 0

Not really telling me much..

Also do switchs in the CLIENT mode take part in prunning? I read some where they do not, but it seems to be shown as enababled.

Cheers

jason_lunde

I think what you are looking for will be in the output of:
show int trunk

at the bottom there is a section
Vlans in spanning tree forwarding state and not pruned**

It will list the vlans that are forwarding on the trunk. The one switch without the vlan should not show it in this forwarding list.

Also, once you enable it on the vtp server, the clients automatically start pruning.

DevilWAH

jason_lunde wrote: »

I think what you are looking for will be in the output of:
show int trunk

at the bottom there is a section
Vlans in spanning tree forwarding state and not pruned**

It will list the vlans that are forwarding on the trunk. The one switch without the vlan should not show it in this forwarding list.

Also, once you enable it on the vtp server, the clients automatically start pruning.

That the one cheers

could I jsut ask what exactly is meant by the management domain? (is this the VTP managment domain?)

Port Vlans allowed and active in management domain
Gi1/0/23 1,300,350,500
Gi1/0/24 1,300,350,500

CiskHo

DevilWAH wrote: »

...what exactly is meant by the management domain? (is this the VTP managment domain?)

Yes, that is the VTP domain.

APA

To see it in action -

Make sure VLAN300 has no ports assigned or SVIs on one of the switches, this switch should only know about VLAN300 via the VTP updates from the VTP server.

If pruning is enabled correctly you should then be able to execute 'sh int trunk' on the upstream switch and see that is has now pruned VLAN300 from the relevant trunk link to the switch downstream which has no members in VLAN300

wave

Hey there,

I just attempted this lab. Except I assigned ports to vlan 300 on all switches. Both the top and bottom switch show they are forwarding for vlan 300 but the middle switch doesn't include 300 in the "Vlans in spanning tree forwarding state and not pruned" list.

Why would that be?

networker050184

wave wrote: »

Hey there,

I just attempted this lab. Except I assigned ports to vlan 300 on all switches. Both the top and bottom switch show they are forwarding for vlan 300 but the middle switch doesn't include 300 in the "Vlans in spanning tree forwarding state and not pruned" list.

Why would that be?

Are you running VTP? Have you verified that the switches are receiving the correct info via STP? If you only build VLANs manually you will only see what your create.

Also keep in mind if you have down stream switches that need this VLAN it won't be pruned. That would essentially cut off the communication in that VLAN.

wave

Yes VTP is running and all switches have the same revision number. VLAN 300 appears on all 3 switches.

pham0329

Aside from show int trunk, you can also try show interface interface_type pruning to see what vlan has been pruned from the interface

R1#show int fa 0/12 pruning

Port Vlans pruned for lack of request by neighbor
Fa0/12 10,20,30,40,50

Port Vlan traffic requested of neighbor
Fa0/12 1,10,20,30,40

Sw2#show int fa 0/12 pruning

Port Vlans pruned for lack of request by neighbor
Fa0/12 50

Port Vlan traffic requested of neighbor
Fa0/12 1

As you can see, R1 pruned vlan 10,20,30,40,50 because Sw2 was only requesting VLAN 1. Sw2 pruned VLAN 50 because R1 was only requesting VLAN 1,10,20,30,40

wave

Thanks pham. I still have the same issue.

I'm wondering whether traffic has to be generated on the ports in VLAN 300 on each switch before it will show in the "Vlans in spanning tree forwarding state and not pruned" list.

I had thought all VTP was looking for was ports assigned to X vlan on each switch...Anyone know the answer to this?

wave

Depending which output I'm reading, I get a different feeling of what might be happening.

I just ran a #show interfaces port pruning and got this:

Port Vlans pruned for lack of request by neighbor
Fa0/23 2,4,300

Port Vlan traffic requested of neighbor
Fa0/23 1-2,300

Remembering that each of the three switches has a port in Vlan 300 (and others that are in VLAN 2 for the matter).

It would appear from this output that THIS switch has pruned VLANS 2,4,300 because it hasn't had any requests for them.

Interpreting the second part, it looks like the neighbor switch has had requests for VLANS 1-2,300 from the switch above it?

pham0329

Port Vlans pruned for lack of request by neighbor
Fa0/23 2,4,300

That output basically means that VLAN 300 was pruned because the switch connected to that interface isn't requesting traffic for vlan 300. Check the config for the upstream switch

Port Vlan traffic requested of neighbor
Fa0/23 1-2,300

Interpreting the second part, it looks like the neighbor switch has had requests for VLANS 1-2,300 from the switch above it?

The second part tells you what VLANs the switch (that's you're on) is requesting from the switch connected port fa 0/23.

wave

Aha! I think I've got it.

I shutdown vlan 1 and assigned an ip to vlan 300 on all switches, then brought those vlans up.

I then fired a few pings back and forth. Now v 300 disappeared from the "
Port Vlans pruned for lack of request by neighbor" list and is showing in the "requested traffic" list too.

So it's not just about which ports are assigned to which vlans, traffic actually has to be moving before you see pruning changes.