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Vlan on L3 switch to L2 switch

Ed Willson

I hope this is a simple one...We have a pretty flat network. Native vlan, and vlan 15. Until now vlan 15 only exists on the core switch.Im adding a L2 10gb switch for San traffic. It is configured for native vlan and 15.

I have a .1q trunk between them and it's up and up, all vlans allowed.

If i plug a laptop into l2 switch on vlan 15 and try to ping the vlan 15 on the l3 switch I get no reply.

6 Replies 6

Carlos Villagran
Cisco Employee
Cisco Employee

Please make sure vlan 15 is really configured in the switch and a device is connected to a port belonging to vlan 15 using the command  show vlan brief. 

Also please make sure the trunk is visible in both sides and all vlans are permitted in both sides of the trunk.

Hope it helps, best regards!


The vlan is on both sides. The trunk visible and the access port the laptop is plugged into is vlan 15.

If I give the vlan an IP address on the the l2 switch I can ping the laptop from the l2 switch.

Hi Ed!

Can you check if L3 switch is registering the Laptop's MAC address? If so, can you check if there is an ARP entry in your laptop?

Is your SVI in up/up state?

Best regards!


InayathUlla Sharieff
Cisco Employee
Cisco Employee

Okay here is the go:-

PC---vlan15--(L2-Switch)====Trunk=====(L3-Switch)-Layer3 Vlan15.

Verification already done:-


1- Vlan 15 at both the ends are on the same network.(PC vlan ip address and L3 vlan on layer3 sw). Vlan showing as active and healthy at both the switches and respective ports are showing as part of the vlan(show vlan id 15 is the cmd to verify).

2- show int trunk -> show vlan 15 on the trunk link and in forwarding state not pruned.(Basically i mean STP checking) & also vlan 15 is not the native vlan on either of the switches.

3- Layer 2 switch also displays the PC port under vlan15 active interfaces.

4- But if you configure the SVI 15 on layer2 and pc is able to ping it.

Next action:


++Could you check if  interface vlan 15 of L2 is pingable from L3 switch? ( configure same network int vlan 15 on both the switches and see if those are reachable).

++ Please paste the following outputs:-

a- PC ip address along with subnet mask.

b- Show vlan id 15 & show int trunk  --> from both the switches.

c- Trunk interface configuration from both the switches.

d- Layer 3 SVI of vlan 15 configuration from Core device.

e- Show spanning tree vlan 15.




Thanks - it will be tomorrow morning. 

Also the switches involved are a 3750x stack running LAN base and Dell n4032f stack.

Ed Willson

I have gotten this figured out. It turn out Dell switches do trunking in quite an odd way. It turns out that I had to use what they call a General port. The general port is a trunk will allow untagged and tagged packets. I also had to specify that the vlan 15 packets were going to be tagged. The command that got it going was:

switchport general allowed vlan add 15 tagged


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