VLAN Stacking Overview
Configuring VLAN Stacking
page 33-6
OmniSwitch AOS Release 7 Network Configuration Guide
June 2013
How VLAN Stacking Works
On the Provider Edge bridge (PE), a unique tunnel (SVLAN) ID is assigned to each customer. The tunnel
ID corresponds to a VLAN ID, which is created on the switch when the tunnel is configured. For exam-
ple, when tunnel 100 is created, VLAN Stacking software interacts with VLAN Manager software to
configure a VLAN 100 on the switch. VLAN 100 is the provider bridge VLAN that will tunnel customer
VLAN traffic associated with tunnel 100. So, there is a one to one correspondence between a tunnel and
its provider bridge VLAN ID. In fact, tunnel and VLAN are interchangeable terms when referring to the
provider bridge configuration.
VLAN Stacking refers to the tunnel encapsulation process of appending to customer packets an 802.1Q
tag that contains the tunnel ID associated to that customer’s provider bridge port and/or VLANs. The
encapsulated traffic is then transmitted through the Ethernet metro area network (EMAN) cloud and
received on another PE bridge that contains the same tunnel ID, where the packet is then stripped of the
tunnel tag and forwarded to the traffic destination.
The following provides an example of how a packet ingressing on a VLAN Stacking UNI port that is
tagged with the customer VLAN (CVLAN) ID transitions through the VLAN Stacking encapsulation
process:
1
Packet with CVLAN tag ingressing on a user port.
2
Double Tagging
inserts the SVLAN tag in the packet. The packet is sent out the network port with
double tags (SVLAN+CVLAN).
3
VLAN Translation
replaces the CVLAN Tag with SVLAN Tag. The packet is sent out the network
port with a single tag (SVLAN).
CVLAN Tag
(4)
MAC DA
(6)
MAC SA
(6)
ETYPE
0x0800
Payload
CVLAN Tag
(4)
SVLAN Tag
(4)
MAC DA
(6)
MAC SA
(6)
ETYPE
0x0800
Payload
SVLAN Tag
(4)
MAC DA
(6)
MAC SA
(6)
ETYPE
0x0800
Payload