Am I missing something with trunking an interface?

[danielrattee]

Hello, I feel like I am going crazy.

I have a PLC that is on VLAN 10, and production clients and label printers that are on VLAN 100.

Vlan 10 IP range is 172.18.XX.0 range

VLAN 100 is on 10.68.XX.0 range.

C2960 switch

Gi1/0/38 is connected to a smaller "dumb" switch, and the printers, clients, and PLC are connected to that.

If configuring Gi1/0/38 for VLAN 100

switchport access vlan 100
switchport mode access

I can of course ping things on the VLAN 100 network.

Same thing with VLAN 10

switchport access vlan 10
switchport mode access

What I am getting frustrated over is when I configure the interface as a trunk.

switchport trunk allowed vlan 10,100
switchport mode trunk

I am unable to ping any device. I have set the native VLAN (10), I have not put in the "allow" command and left it open as below from the show interfaces trunk command

XXXXXsw-80#show interfaces trunk

Port Mode Encapsulation Status Native vlan
Gi1/0/38 on 802.1q trunking 10
Gi1/0/48 on 802.1q trunking 10
Gi1/0/49 on 802.1q trunking 10

Port Vlans allowed on trunk
Gi1/0/38 1-4094
Gi1/0/48 1,10,100-101,200,412,500,810
Gi1/0/49 1-4094

Port Vlans allowed and active in management domain
Gi1/0/38 1,10,100-101,200,412,500,810,900
Gi1/0/48 1,10,100-101,200,412,500,810
Gi1/0/49 1,10,100-101,200,412,500,810,900

Port Vlans in spanning tree forwarding state and not pruned
Gi1/0/38 100
Gi1/0/48 1,10,100-101,200,412,500,810
Gi1/0/49 1,10,100-101,200,412,500,810,900

I'm not sure what I am missing? I even went back to where the machine used to be connected to and gave it the same configuration that was on its other switch.

[Flavio Miranda]

Hi @danielrattee 

 Are you configuring trunk between the 2960 and the " smaller "dumb"" ?  

[balaji.bandi]

Gi1/0/38 is connected to a smaller "dumb" switch, and the printers, clients, and PLC are connected to tha

i don't think Dumb switch can understand dot1q - so you have limitation using as single VLAN as access port

[Joseph W. Doherty]

What I am getting frustrated over is when I configure the interface as a trunk.

switchport trunk allowed vlan 10,100
switchport mode trunk

I am unable to ping any device.

From what you've earlier described, that's expected behavior.  As @balaji.bandi notes, the dumb switch doesn't understand .1q tagged frames.

I have set the native VLAN (10), I have not put in the "allow" command and left it open as below from the show interfaces trunk command

Okay, after you do that, your dumb switch might allow VLAN 10 to work again, but VLAN 100 still won't work.

What native does, is remove that VLAN's frame tags.