Cisco Catalyst 4500 series Administration Manual page 794

About VLAN Mapping
Figure 29-4
Cat4K
Customer A
edge switch
Cat4K
Customer B
edge switch
Cat4K
Customer B
edge switch
All forwarding operations on the Catalyst 4500 series switch are performed using S-VLAN and not
C-VLAN information because the VLAN ID is mapped to the S-VLAN on ingress.
When you configure features on a port configured for VLAN mapping, you always use the S-VLAN
Note
rather than the customer VLAN-ID (C-VLAN).
On an interface configured for VLAN mapping, the specified C-VLAN packets are mapped to the
specified S-VLAN when they enter the port. Symmetrical mapping to the customer C-VLAN occurs
when packets exit the port.
The switch supports these types of VLAN mapping on UNI trunk ports:
One-to-one VLAN mapping occurs at the ingress and egress of the port and maps the customer
•
C-VLAN ID in the 802.1Q tag to the service-provider S-VLAN ID. You can also specify that packets
with all other Vlan Ids are dropped. See the
• Traditional 802.1Q tunneling (QinQ) performs all-to-one bundling of C-VLAN IDs to a single
S-VLAN ID for the port. The S-VLAN is added to the incoming unmodified C-VLAN. You can
configure the UNI as an 802.1Q tunnel port for traditional QinQ, or you can configure selective
QinQ on trunk ports for a more flexible implementation. Mapping takes place at ingress and egress
of the port. All packets on the port are bundled into the specified S-VLAN. See the
Q-in-Q on a Trunk Port" section on page
• Selective QinQ maps the specified customer VLANs entering the UNI to the specified S-VLAN ID.
The S-VLAN is added to the incoming unmodified C-VLAN. You can also specify that traffic
carrying all other customer VLAN IDs is dropped. See the
section on page
Untagged packets enter the switch on the trunk native VLAN and are not mapped.
Note
For quality of service (QoS), the switch supports flexible mapping between C-CoS or C-DSCP and
S-CoS, and maps the inner CoS to the outer CoS for traffic with traditional QinQ or selective QinQ
VLAN mapping.
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
29-8
Chapter 29
Layer 2 VPN Deployment
VLAN translation
configured TRUNK
PORTS
SP
Cat4K
29-12.
Configuring 802.1Q Tunneling, VLAN Mapping, and Layer 2 Protocol Tunneling
SP
Cat4K
SP Network
"One-to-One Mapping" section on page
29-12.
"Selective Q-in-Q on a Trunk Port"
VLAN translation
configured TRUNK
PORTS
Cat4K
Customer A
edge switch
SP
Cat4K
Cat4K
Customer B
edge switch
29-11.
"Traditional
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