Configuring Layer 2 Protocol Tunneling; Default Layer 2 Protocol Tunneling Configuration; Table 8-1 Default Layer 2 Protocol Tunneling Configuration - Cisco ONS 15454 Software Feature And Configuration Manual

Chapter 8 Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
protocol tunneling is enabled, Layer 2 protocols within each customer's network are totally separate
from those running within the service-provider network. Customer switches on different sites that send
traffic through the service-provider network with IEEE 802.1Q tunneling achieve complete knowledge
of the customer's VLAN. If IEEE 802.1Q tunneling is not used, you can still enable Layer 2 protocol
tunneling by connecting to the customer switch through access ports and enabling tunneling on the
service-provider access port.

Configuring Layer 2 Protocol Tunneling

You enable Layer 2 protocol tunneling (by protocol) on the tunnel ports that are connected to the
customer in the edge switches of the service-provider network. ML-Series card tunnel ports are
connected to customer IEEE 802.1Q trunk ports. The ML-Series card supports Layer 2 protocol
tunneling for CDP, STP, and VTP. The ML-Series cardes connected to the customer switch perform the
tunneling process.
When the Layer 2 PDUs that entered the inbound ML-Series switch through the tunnel port exit the
switch through the trunk port into the service-provider network, the switch overwrites the customer
PDU-destination MAC address with a well-known Cisco proprietary multicast address
(01-00-0c-cd-cd-d0). If IEEE 802.1Q tunneling is enabled, packets are also double-tagged; the outer tag
is the customer metro tag and the inner tag is the customer VLAN tag. The core switches ignore the inner
tags and forward the packet to all trunk ports in the same metro VLAN. The ML-Series switches on the
outbound side restore the proper Layer 2 protocol and MAC address information and forward the
packets. Therefore, the Layer 2 PDUs are kept intact and delivered across the service-provider
infrastructure to the other side of the customer network.
This section contains this information about configuring Layer 2 protocol tunneling:
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Default Layer 2 Protocol Tunneling Configuration

Table 8-1
Table 8-1
Feature
Layer 2 protocol tunneling
Class of service (CoS) value
Cisco ONS 15454 SONET/SDH ML-Series Multilayer Ethernet Card Software Feature and Configuration Guide, R4.0
78-15224-02
Default Layer 2 Protocol Tunneling Configuration, page 8-7
Layer 2 Protocol Tunneling Configuration Guidelines, page 8-8
Monitoring and Verifying Tunneling Status, page 8-9
shows the default Layer 2 protocol tunneling configuration.
Default Layer 2 Protocol Tunneling Configuration
Default Setting
Disabled for CDP, STP, and VTP.
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 configured, there is no default. This allows existing
CoS values to be maintained, unless the user configures
otherwise.
Configuring Layer 2 Protocol Tunneling
8-7