Confirm my thinking - Native Vlan

[John Blakley]

All,

Long time no speak!

I've got a 3750 that has some vlans configured on it. We're moving a complete location to our corporate office, and I'm wanting to keep them the same way that they are over there. When they come in, they'll be getting rid of a router. I was going to create a vlan for their existing subnet and give them a L2 switch. I was then going to create the vlans on the L2 switch and change their native vlan to be the vlan that I created for their subnet. On the 3750 for that one port, I would change the native vlan to the vlan for their subnet. The native vlans for all of the other ports on the 3750 would be vlan 1. I think it should work in concept.

Thanks!

John

[Giuseppe Larosa]

Hello John,

native vlan plays a role on L2 trunk links.

if all ports are in vlan 1, or the uplink is a L2 trunk and you use vlan1 as native vlan on L2 switch side with native vlan X on the other side, or you need to put the port in vlan 1 too but you make it an access port.

I would use a cleaner design:

make the L2 switch a VTP transparent device, create the vlan X that is also in the campus, use a trunk port that allows all vlans of interest including vlan X.

access ports can be configured in access mode in vlan X.

playing on a mismatch of native vlan on the two sides of a trunk is not a clean design.

Hope to help

Giuseppe

[John Blakley]

Giuseppe,

It wouldn't be mismatched. Here's what I've got:

Cisco 3750:

g3/0/28: Trunked to Dell 3548

Dell 3548 Port 48 Trunked to 3750 g3/0/28

On the 3750, for this Dell switch, I would have Vlan's 10 and 95.

The Dell would be configured for all ports to be trunked because of VoIP phones, so all ports are VLAN 10 and 95. The workstation will come in on 95 untagged, and the phone will be forced to VLAN 10.

The 3750 for g3/0/28 will be trunked and allow 10 and 95 over that trunk. Vlan 1 should never go over it. Vlan 1 comes into play with my other edge switches, say g2/0/28. The native vlan for that port would be 1. Does that make sense? I'm trying to lock the Dell switch into the VLAN that I want the workstations to come in on. If I allowed them on vlan 1, I'd get the wrong subnet assigned.

I'm actually going to put this in a lab tomorrow.

Thanks,

John

[Jon Marshall · Accepted solution]

John

This will work absolutely fine. The native vlan is relevant to the specific trunk port so you can have all your other trunks with native vlan 1 but the port connecting to the dell switch with a native vlan of 95.

Edit - this is assuming the Dell switch supports 802.1q trunks.

By the way, how have you been. Haven't seen you on these forums for a while.

Jon

[John Blakley]

I've been doing really good. I'm studying for CISSP right now, so I've been head deep in books. There are large projects going on at the office too, so I haven't had much of a chance to get on here. I need to start hanging out here more often again.....

Thank you!!