Debugging Vlan Stacking; Vlan Stacking In Multi-Vendor Networks - Dell C9000 Series Networking Configuration Manual

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Debugging VLAN Stacking

To debug VLAN stacking, use the following command.

Debug the internal state and membership of a VLAN and its ports.

debug member

Example of Debugging a VLAN and its Ports

The port notations are as follows:

MT — stacked trunk

MU — stacked access port

T — 802.1Q trunk port

U — 802.1Q access port

NU — Native VLAN (untagged)

Dell# debug member vlan 603

: Te 1/47 (MT), Te 2/1(MU), Te 2/25(MT), Te 2/26(MT), Te 2/27(MU)

Dell#debug member port tengigabitethernet 1/47

: 603 (MT), 100(T), 101(NU)

The first field in the VLAN tag is the tag protocol identifier (TPID), which is 2 bytes. In a VLAN-stacking

network, after the frame is double tagged, the outer tag TPID must match the TPID of the next-hop system.

While 802.1Q requires that the inner tag TPID is 0x8100, it does not require a specific value for the outer tag

TPID. Systems may use any 2-byte value. The switch uses 0x9100 (shown in the following) while non-Dell

Networking devices might use a different value.

If the next-hop system's TPID does not match the outer-tag TPID of the incoming frame, the system drops

the frame. For example, as shown in the following, the frame originating from Building A is tagged VLAN RED,

and then double-tagged VLAN PURPLE on egress at R4. The TPID on the outer tag is 0x9100. R2's TPID must

also be 0x9100, and it is, so R2 forwards the frame.

Given the matching-TPID requirement, there are limitations when you employ Dell Networking systems at

network edges, at which, frames are either double tagged on ingress (R4) or the outer tag is removed on

egress (R3).

Service Provider Bridging