Owner's Manual

781
Chapter 30. vMAN (PBN) 8800 Chassis Switch
Figure 96. vMAN
The entry points to the vMAN are the access ports on the vMAN edge switches, which
function as PBs. Customer VLAN traffic that is addressed to locations at other vMAN access
ports enters the ingress access port, is switched through the vMAN, and exits the egress
access port. If you do not configure any frame manipulation options, the frames that exit the
vMAN are identical to the frames that entered the vMAN.
All vMAN ports except the access ports are vMAN network ports. The configuration of the
network ports establishes the vMAN.
Figure 96 shows two terms that are used during vMAN configuration: untagged vman port
and tagged vman port. When you configure a vMAN, you create and configure a vman in
software, and then you add ports to it. An untagged vman port represents a vMAN access
port, and despite its name, an untagged vman port supports tagged and untagged VLAN
frames. A tagged vman port represents a vMAN network port, and it only supports tagged
vMAN frames.
A vMAN supports two tags in each Ethernet frame, instead of the single tag supported by a
VLAN Ethernet frame. The inner tag is referred to as the customer tag (C-tag), and this
optional tag is based on the VLAN tag if the source VLAN is a tagged VLAN. The outer tag is
referred to as the service tag (S-tag) or vMAN tag, and it is the tag that is used to switch the
frame through the vMAN.
Figure 97 shows the frame manipulation that occurs at the access
switch for a vMAN.
Figure 97. Tag Usage at the vMAN Access Switch
VLAN 1
VLAN 2
vMAN
vMAN
access
ports
(untagged
vman
ports)
vMAN
network
ports
(tagged
vman
ports)
VLAN 1
VLAN 2
vMAN
access
ports
(untagged
vman
ports)
vMAN
network
ports
(tagged
vman
ports)
EX_vman_0001A
VMAN 1
VMAN 2
1.1
1.2
2.1
2.2
MAC DA
MAC SA
S-tag
(32 b, expected)
VLAN tag or
C-tag (optional)
L2 PDU
MAC DA
MAC SA
VLAN tag or
C-tag (optional)
L2 PDU
Tagged port
Tagged port
Untagged port
Untagged port
EX_vman_0037