Cisco Catalyst 4500 Series Administration Guide

29-16
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
OL_28731-01
Chapter 29 Configuring 802.1Q Tunneling, VLAN Mapping, and Layer 2 Protocol Tunneling
Configuring Layer 2 Protocol Tunneling
• Layer 2 Protocol Tunneling Configuration Guidelines, page 29-16
• Configuring Layer 2 Tunneling, page 29-17
Default Layer 2 Protocol Tunneling Configuration
Table 29-1 shows the default configuration for Layer 2 protocol tunneling.
Layer 2 Protocol Tunneling Configuration Guidelines
These are some configuration guidelines and operating characteristics of 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, access ports or trunk ports.
• Dynamic Trunking Protocol (DTP) is not compatible with Layer 2 protocol tunneling because you
must manually configure asymmetric links with tunnel ports and trunk ports.
• EtherChannel port groups are compatible with tunnel ports when the 802.1Q configuration is
consistent within an EtherChannel port group.
• If an encapsulated PDU (with the proprietary destination MAC address) is received on a port with
Layer 2 tunneling enabled, the port is shut down to prevent loops.
• The port also shuts down when a configured shutdown threshold for the protocol is reached. You can
manually reenable the port (by entering a shutdown and a no shutdown command sequence). If
errdisable recovery is enabled, the operation is retried after a specified time interval.
• Only decapsulated PDUs are forwarded to the customer network. The spanning-tree instance
running on the service provider network does not forward BPDUs to Layer 2 protocol tunneling
ports. CDP packets are not forwarded from Layer 2 protocol tunneling ports.
• When protocol tunneling is enabled on an interface, you can set a per-protocol, per-port, shutdown
threshold for the PDUs generated by the customer network. If the limit is exceeded, the port shuts
down. You can also limit the BPDU rate by using QoS ACLs and policy maps on a Layer 2 protocol
tunneling port.
• When protocol tunneling is enabled on an interface, you can set a per-protocol, per-port, drop
threshold for the PDUs generated by the customer network. If the limit is exceeded, the port drops
PDUs until the rate at which it receives them is below the drop threshold.
Table 29-1 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 configured, the
default is 5.

Cisco Catalyst 4500 Series Specifications

General

Series	Catalyst 4500 Series
Category	Switch
Layer Support	Layer 2, Layer 3
Form Factor	Modular chassis
Stackable	No
Chassis Slots	3, 6, 7, 10
Power Supply Options	AC, DC
Redundancy	Power supply, Supervisor engine
Network Management	Cisco IOS Software CLI, SNMP, Cisco Prime Infrastructure
Features	Security, QoS
Port Density	Up to 384 ports per chassis
Security Features	802.1X, ACLs, DHCP Snooping, Dynamic ARP Inspection, IP Source Guard
Supervisor Engine	8-E