Cisco Catalyst 4500 Series - Page 680

27-8
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
OL-25340-01
Chapter 27 Configuring 802.1Q Tunneling, VLAN Mapping, and Layer 2 Protocol Tunneling
About VLAN Mapping
Figure 27-4 Layer 2 VPN Deployment
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.
Note When you configure features on a port configured for VLAN mapping, you always use the S-VLAN
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 “One-to-One Mapping” section on page 27-11.
• 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 “Traditional
Q-in-Q on a Trunk Port” section on page 27-12.
• 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 “Selective Q-in-Q on a Trunk Port”
section on page 27-12.
Note Untagged packets enter the switch on the trunk native VLAN and are not mapped.
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.
Cat4K
Customer A
edge switch
Cat4K
Customer B
edge switch
Cat4K
Customer B
edge switch
Cat4K
Customer A
edge switch
Cat4K
Customer B
edge switch
SP
Cat4K
SP
Cat4K
SP
Cat4K
SP Network
VLAN translation
configured TRUNK
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VLAN translation
configured TRUNK
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