Cisco Catalyst 4500 Series Administration Guide

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Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)SG
OL-30933-01
Chapter 5 Configuring Virtual Switching Systems
Configuring a VSS
Configuring Dual-Active Detection
The following sections describe how to configure dual-active detection:
• Configuring Enhanced PAgP Dual-Active Detection, page 5-51
• Configuring Fast-Hello Dual-Active Detection, page 5-52
• Displaying Dual-Active Detection, page 5-53
Configuring Enhanced PAgP Dual-Active Detection
If enhanced PAgP is running on the MECs between the VSS and its access switches, the VSS can use
enhanced PAgP messaging to detect a dual-active scenario.
By default, PAgP dual-active detection is enabled. However, the enhanced messages are only sent on port
channels with trust mode enabled (see the trust mode description in the note).
Note Before changing PAgP dual-active detection configuration, ensure that all port channels with trust mode
enabled are in administrative down state. Use the shutdown command in interface configuration mode
for the port channel. Remember to use the no shutdown command to reactivate the port channel when
you are finished configuring dual-active detection.
To enable or disable PAgP dual-active detection, perform this task:
You must configure trust mode on the port channels that will detect PAgP dual-active detection. By
default, trust mode is disabled.
Note If PAgP dual-active detection is enabled, you must place the port channel in administrative down state
before changing the trust mode. Use the shutdown command in interface configuration mode for the port
channel. Remember to use the no shutdown command to reactivate the port channels when you are
finished configuring trust mode on the port channel.
To configure trust mode on a port channel, perform this task:
This example shows how to enable PAgP dual-active detection:
Switch(config)# interface port-channel 20
Switch(config-if)# shutdown
Switch(config-if)# exit
Switch(config)# switch virtual domain 100
Command Purpose
Step 1
Switch(config)# switch virtual domain domain_id
Enters virtual switch submode.
Step 2
Switch(config-vs-domain)# dual-active detection pagp
Enables sending of the enhanced PAgP messages.
Command Purpose
Step 1
Switch(config)# switch virtual domain domain_id
Enters virtual switch submode.
Step 2
Switch(config-vs-domain)# dual-active detection pagp
trust channel-group group_number
Enables trust mode for the specified port channel.

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