Layer 2 Protocol Tunneling Configuration Guidelines; Configuring A Layer 2 Tunneling Port - Cisco ONS 15454 Software Feature And Configuration Manual
Sonet / sdh ml-series multilayer ethernet card
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Configuring Layer 2 Protocol Tunneling
Layer 2 Protocol Tunneling Configuration Guidelines
These are some configuration guidelines and operating characteristics of Layer 2 protocol tunneling:
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Configuring a Layer 2 Tunneling Port
Beginning in privileged EXEC mode, follow these steps to configure a port as a Layer 2 tunnel port:
Command
Step 1
Router# conf t
Step 2
Router(config)# bridge bridge-number
protocol bridge-protocol
Step 3
Router(config)# l2protocol-tunnel cos
cos-value
Step 4
Router(config)# interface fastEthernet
number
Step 5
Router(config-if)# bridge-group number
Step 6
Router(config-if)# mode dot1q-tunnel
Step 7
Router(config-if)# l2 protocol-tunnel
[cdp][stp][vtp]
Cisco ONS 15454 SONET/SDH ML-Series Multilayer Ethernet Card Software Feature and Configuration Guide, R4.0
8-8
The switch supports tunneling of CDP, STP (including multiple STP [MSTP], and VTP protocols.
Protocol tunneling is disabled by default but can be enabled for the individual protocols on
IEEE 802.1Q tunnel ports.
Tunneling is not supported on trunk ports. If you enter the l2protocol-tunnel interface configuration
command on a trunk port, the command is accepted, but Layer 2 tunneling does not take affect unless
you change the port to a tunnel port.
EtherChannel port groups are compatible with tunnel ports as long as the IEEE 802.1Q
configuration is consistent within an EtherChannel port group.
If an encapsulated PDU (with the proprietary destination MAC address) is received from a tunnel
port or access port with Layer 2 tunneling enabled, the tunnel port is shut down to prevent loops.
Only decapsulated PDUs are forwarded to the customer network. The spanning tree instance running
on the service-provider network does not forward BPDUs to tunnel ports. No CDP packets are
forwarded from tunnel ports.
Because tunneled PDUs (especially STP BPDUs) must be delivered to all remote sites for the
customer virtual network to operate properly, you can give PDUs higher priority within the
service-provider network than data packets received from the same tunnel port. By default, the
PDUs use the same CoS value as data packets.
Protocol tunneling has to be configured symmetrically at both the ingress and egress point. For
example, if you configure the entry point to tunnel STP, CDP, VTP, then you must configure the
egress point in the same way.
Chapter 8
Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Purpose
Enters global configuration mode.
Creates a bridge number and specifies a protocol.
Assigns a CoS value or values to associate with the Layer 2 tunneling
port. The cos-value is a number from the 0 to 7 range.
Enters the interface configuration mode and the interface to be
configured as a tunnel port. This should be the edge port in the
service-provider network that connects to the customer switch. Valid
interfaces include physical interfaces and port-channel logical
interfaces (port channels 1 to 64).
Specifies the default VLAN, which is used if the interface stops
trunking. This is VLAN ID specific to the particular customer.
Sets the interface as an IEEE 802.1Q tunnel port.
Sets the interface as a Layer 2 protocol tunnel port and enables Cisco
Discovery Protocol (CDP), Spanning Tree (STP) and VLAN Trunking
Protocol (VTP), which are off by default.
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