problems with vlan between distribution switches

[GiordanoMonacelli1623]

Hello Dear All

In the network of the company I work for we have several VLANs, where backbone is acting as server fot VTP

I don't know why, but only a particular VLAN is not communicating between all switches

now, the problem is that I do not have access to the backbone but only to every distribution switch and configurations are all the same, I tried to check and compare all vtp - vlan - interface configuration and everything seems absolutely equal on every switch.

is there any setting to be made on the backbone to allow a vlan to communicate between switches?

at distribution switch level everything seems ok, all vlans seem to be passing trought trunk

[Seb Rupik]

Hi there,

Is VTP Pruning enable on the VTP Sever?

Does the switch in question have active switchports in the VLAN? If not then the VLAN will be pruned, sh int trunk will confirm this.

cheers,

Seb.

[GiordanoMonacelli1623]

unfortunately I cannot access on the VTP server, but if I launch the command

sh int trunk on distribution switches, I can see that on trunk port all vlans are correctly propagated
also if I run the command show vlan summary, I get the same number of vlans on all switches (on those where is working and on those where is not working)

is it possible that on backbone administrators allowed this particular vlan only on some distribution switches?

[Seb Rupik]

The VLAN database (sh vlan) will be populated via VTP, in this case it is not relevant. The sh int trunk will of course show the VLANs tagged on the trunk, but what I am interested in is the detail of the output regarding VLAN pruning.

Can you share the complete sh int trunk output from the distribution switches?

Also the output of sh vtp status

If VTP pruning is enabled it would not make sense for the backbone admins to not trunk all VLANs on the downlinks to the distribution switches.

Can you also confirm that the offending VLAN is configured a mode access on the distribution switch itself or on an access-layer switch further down in the topology.

cheers,

Seb.