Default Layer 2 Protocol Tunneling Configuration - Cisco Catalyst 3550 series Software Configuration Manual

Configuring Layer 2 Protocol Tunneling
See
Asymmetric links connect the Customers in Site 1 to edge switches in the SP network. The Layer 2 PDUs
(for example, BPDUs) coming into Switch 2 from Customer B 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 4, the metro 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 B on Site 2 as a single-tagged frame in VLAN 100.
You can also enable Layer 2 protocol tunneling on access ports on the edge switch connected to access
ports on the customer switch. In this case, the encapsulation and de-encapsulation process is the same
as described in the previous paragraph, except that the packets are not double-tagged in the SP network.
The single tag is the customer-specific access VLAN tag.
This section has this information about configuring Layer 2 protocol tunneling:
•
•
•
•

Default Layer 2 Protocol Tunneling Configuration

Table 15-1
Table 15-1 Default Layer 2 Ethernet Interface VLAN Configuration
Feature
Layer 2 protocol tunneling
Shutdown threshold
Drop threshold
CoS value
Layer 2 Protocol Tunneling Configuration Guidelines
These are some configuration guidelines and operating characteristics of Layer 2 protocol tunneling:
•
•
•
•
Catalyst 3550 Multilayer Switch Software Configuration Guide
15-10
Figure 15-4, with Customer A and Customer B in access VLANs 30 and 40, respectively.
Default Layer 2 Protocol Tunneling Configuration, page 15-10
Layer 2 Protocol Tunneling Configuration Guidelines, page 15-10
Configuring Layer 2 Tunneling, page 15-11
Configuring Layer 2 Tunneling for EtherChannels, page 15-13
shows the default configuration for Layer 2 protocol tunneling.
The switch supports tunneling of CDP, STP, including multiple STP (MSTP), and VTP. Protocol
tunneling is disabled by default but can be enabled for the individual protocols on 802.1Q tunnel
ports or on access ports.
The switch supports PAgP, LACP, and UDLD tunneling for emulated point-to-point network
topologies. Protocol tunneling is disabled by default but can be enabled for the individual protocols
on 802.1Q tunnel ports or on access ports.
If you enable PAgP or LACP tunneling, we recommend that you also enable UDLD on the interface
for faster link-failure detection.
Loopback detection is not supported on Layer 2 protocol tunneling of PAgP, LACP, or UDLD
packets.
Chapter 15
Default Setting
Disabled.
None set.
None set.
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, the
default is 5.
Configuring 802.1Q and Layer 2 Protocol Tunneling
78-11194-09