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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
OL-13270-01
Chapter16 Configuring IEEE 802.1Q and L ayer 2 Protocol Tunneling Configuring Layer 2 Protocol Tunneling
See Figure 16-4, with Customer X and Customer Y in access VLANs 30 and 40, respectively.
Asymmetric links connect the customers in Site 1 to edge switches in the service-provider network. The
Layer 2 PDUs (for example, BPDUs) coming into Switch B from Customer Y in Site 1 are forwarded to
the infrastructure as double-tagged packets with the well-known MAC address as the destination MAC
address. These double-tagged packets have the metro VLAN tag of 40, as well as an inner VLAN tag
(for example, VLAN 100). When the double-tagged packets enter Switch D, the outer VLAN tag 40 is
removed, the well-known MAC address is replaced with the respective Layer 2 protocol MAC address,
and the packet is sent to Customer Y on Site 2 as a single-tagg ed f ra me in V LAN 100.
You can also enable Layer 2 protocol tunneling on access ports on the edge switch connected to access
or trunk ports on the customer switch. In this case, the enc ap sulat ion and de caps ul ation pr oc ess is t h e
same as described in the previous paragraph, except that the pac kets ar e not dou ble- t agged i n the
service-provider network. The single tag is the customer-specific access VLAN tag.
In switch stacks, Layer 2 protocol tunneling configuration is distributed among all stack memb ers. Each
stack member that receives an ingress packet o n a local por t enc apsul ates or d ecap sul ates the pac ke t an d
forwards it to the appropriate destination port. On a single switch, ingress Layer 2 protocol-tun neled
traffic is sent across all local ports in the same VLAN on which Layer 2 protocol tunneling is enabled.
In a stack, packets received by a Layer 2 protocol-tunneled port ar e distri buted t o al l por ts i n the stac k
that are configured for Layer 2 protocol tunneling and are in the sa me VLA N. A ll L a yer 2 p rotoc ol
tunneling configuration is handled by the stack master and distributed to all stack members.
These sections contain this configuration information:
•Default Layer 2 Protocol Tunneling Configuration, page 16-11
•Layer 2 Protocol Tunneling Configuration Guidelines, page 16-12
•Configuring Layer 2 Protocol Tunneling, page16-13
•Configuring Layer 2 Tunneling for EtherChannels, page 16-14
Default Layer 2 Protocol Tunneling Configuration
Table16-1 shows the de fault L ayer 2 prot ocol tu nnel ing co nfigurati on.
Table16-1 Default Layer 2 Ethernet Interface VLAN Configuration
Feature Default Setting
Layer 2 protocol tunneling Disabled.
Shutdown threshold None set.
Drop threshold None set.
CoS value If a CoS value is configured on the interface for data packets, that
value is the default used for Layer 2 PDUs. If none is configure d,
the default is 5.