Figure 23-15 – Cisco 15327 User Manual

Page 399

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23-19

Ethernet Card Software Feature and Configuration Guide, R7.2

Chapter 23 E-Series and G-Series Ethernet Operation

E-Series Q-Tagging (IEEE 802.1Q)

Figure 23-15

Q-tag Moving Through VLAN

The ONS node uses the Q-tag attached by the external Ethernet devices that support IEEE 802.1Q.
Packets enter the ONS network with an existing Q-tag; the ONS node uses this same Q-tag to forward
the packet within the ONS network and leaves the Q-tag attached when the packet leaves the ONS
network. The entry and egress ports on the ONS network must be set to Tagged for this process to occur.
Example 2 in

Figure 23-15

illustrates the handling of packets that both enter and exit the ONS network

with a Q-tag.

For more information about setting ports to Tagged and Untag, refer to the Cisco ONS 15454 Procedure
Guide
, the Cisco ONS 15454 SDH Procedure Guide, or the Cisco ONS 15327 Procedure Guide.

Caution

ONS nodes propagate VLANs whenever a node appears on the network view of another node, regardless
of whether the nodes are in the same SONET/SDH network or connect through DCC. For example, if
two ONS nodes without DCC connectivity belong to the same login node group, VLANs propagate
between the two ONS nodes. VLAN propagation happens even though the ONS nodes do not belong to
the same SONET/SDH ring.

Data Flow

No tag

Example 1.
The ONS node uses a
Q-tag internally to deliver
the frame to a specific VLAN.

The receiving ONS node
removes the Q-tag
and forwards the frame
to the specific VLAN.

Example 2.
The ONS node receives
a frame with a Q-tag
and passes it on.

The receiving ONS node
receives a frame with a
Q-tag and passes it on.

No tag

Q-tag

Q-tag

Q-tag

Q-tag

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