Cisco 3550 User Manual

Catalyst 3550 Multilayer Switch

Software Configuration Guide

Cisco IOS Release 12.1(8)EA1

February 2002

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Text Part Number: 78-11194-03

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Catalyst 3550 Multilayer Switch Software Configuration Guide

Copyright © 2002, Cisco Systems, Inc.

All rights reserved.

C O N T E N T S

Preface xxvii

Audience xxvii

Purpose

xxvii

Organization

xxviii

Conventions

xxx

Related Publications

xxxi

Obtaining Documentation

xxxi

World Wide Web

xxxi

Documentation CD-ROM

xxxi

Ordering Documentation

xxxii

Documentation Feedback

xxxii

Obtaining Technical Assistance

xxxii

Cisco.com

xxxiii

Technical Assistance Center

xxxiii

Cisco TAC Web Site

xxxiii

Cisco TAC Escalation Center

xxxiv

Overview

C H A P T E R 1

1-1

Features

1-1

Management Options

1-5

Management Interface Options

1-5

Advantages of Using CMS and Clustering Switches

1-6

Network Configuration Examples

1-7

Design Concepts

1-7

Small to Medium-Sized Network Using Mixed Switches

1-11

Large Network Using Only Catalyst 3550 Switches

1-13

Multidwelling Network Using Catalyst 3550 Switches

1-14

Using the Command-Line Interface

C H A P T E R 2

2-1

IOS Command Modes

2-1

Getting Help

2-3

Abbreviating Commands

2-3

Using no and default Forms of Commands 2-4

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Contents

					Understanding CLI Messages					2-4
					Using Command History				2-5
					Changing the Command History Buffer Size 2-5
					Recalling Commands				2-5
					Disabling the Command History Feature								2-5
					Using Editing Features 2-6
					Enabling and Disabling Editing Features								2-6
					Editing Commands through Keystrokes								2-6
					Editing Command Lines that Wrap							2-8
					Searching and Filtering Output of show and more Commands 2-8
					Accessing the CLI			2-9
					Getting Started with CMS
C H A P T E R 3									3-1
					Features	3-2
					Front Panel View			3-4
					Cluster Tree			3-5
					Front-Panel Images				3-6
						Redundant Power System LED						3-7
						Port Modes and LEDs				3-8
						VLAN Membership Modes					3-9
					Topology View		3-10
					Topology Icons			3-12
					Device and Link Labels 3-13
					Colors in the Topology View 3-14
					Topology Display Options					3-14
					Menus and Toolbar			3-15
					Menu Bar		3-15
					Toolbar		3-21
					Front Panel View Popup Menus						3-22
						Device Popup Menu				3-22
						Port Popup Menu			3-22
					Topology View Popup Menus						3-23
						Link Popup Menu			3-23
						Device Popup Menus				3-24
					Interaction Modes			3-26
					Guide Mode			3-26
					Expert Mode			3-26
					Wizards	3-26
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	Tool Tips 3-27
	Online Help	3-27
	CMS Window Components				3-28
	Host Name List		3-28
	Tabs, Lists, and Tables				3-29
	Icons Used in Windows				3-29
	Buttons	3-29
	Accessing CMS 3-30
	Access Modes in CMS				3-31
	HTTP Access to CMS				3-31
	Verifying Your Changes			3-32
	Change Notification			3-32
	Error Checking		3-32
	Saving Your Changes		3-32
	Using Different Versions of CMS					3-33
	Where to Go Next		3-33
	Assigning the Switch IP Address and Default Gateway 4-1
C H A P T E R 4
	Understanding the Boot Process					4-1
	Assigning Switch Information					4-2
	Default Switch Information					4-3
	Understanding DHCP-Based Autoconfiguration 4-3
	DHCP Client Request Process						4-4
	Configuring the DHCP Server						4-5
	Configuring the TFTP Server						4-5
	Configuring the DNS					4-6
	Configuring the Relay Device						4-6
	Obtaining Configuration Files						4-7
	Example Configuration					4-8

Manually Assigning IP Information	4-10
Checking and Saving the Running Configuration 4-10
Modifying the Startup Configuration	4-12

Default Boot Configuration 4-12

Automatically Downloading a Configuration File 4-12

Specifying the Filename to Read and Write the System Configuration 4-13

	Booting Manually 4-13
	Booting a Specific Software Image	4-14
	Controlling Environment Variables	4-15
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					Scheduling a Reload of the Software Image					4-17
					Configuring a Scheduled Reload 4-17
					Displaying Scheduled Reload Information					4-18
					Clustering Switches
C H A P T E R 5						5-1
					Understanding Switch Clusters			5-2
					Command Switch Characteristics				5-2
					Standby Command Switch Characteristics					5-3
					Candidate and Member Switches Characteristics						5-3
					Planning a Switch Cluster		5-4
					Automatic Discovery of Cluster Candidates and Members								5-4
					Discovery through CDP Hops				5-5
					Discovery through Non-CDP-Capable and Noncluster-Capable Devices 5-6
					Discovery through Different VLANs					5-7
					Discovery through the Same Management VLAN							5-8
					Discovery through Different Management VLANs							5-9
					Discovery through Routed Ports				5-10
					Discovery of Newly Installed Switches 5-11
					HSRP and Standby Command Switches					5-12
					Virtual IP Addresses 5-13
					Automatic Recovery of Cluster Configuration						5-13
					Considerations for Cluster Standby Groups						5-14
					IP Addresses	5-15
					Host Names	5-16
					Passwords	5-16
					SNMP Community Strings			5-16
					TACACS+ 5-17
					Access Modes in CMS		5-17
					LRE Profiles	5-17
					Availability of Switch-Specific Features in Switch Clusters								5-18
					Creating a Switch Cluster		5-18
					Enabling a Command Switch			5-19
					Adding Member Switches			5-20
					Creating a Cluster Standby Group				5-22
					Verifying a Switch Cluster			5-24
					Using the CLI to Manage Switch Clusters 5-25
					Catalyst 1900 and Catalyst 2820 CLI Considerations							5-25
					Using SNMP to Manage Switch Clusters				5-26
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C H A P T E R 6	Administering the Switch 6-1
	Preventing Unauthorized Access to Your Switch	6-1
	Protecting Access to Privileged EXEC Commands	6-2
	Default Password and Privilege Level Configuration 6-3
	Setting or Changing a Static Enable Password	6-3
	Protecting Enable and Enable Secret Passwords with Encryption 6-4
	Disabling Password Recovery 6-5
	Setting a Telnet Password for a Terminal Line	6-6
	Configuring Username and Password Pairs 6-7
	Configuring Multiple Privilege Levels 6-8

	Setting the Privilege Level for a Command					6-8
	Changing the Default Privilege Level for Lines 6-9
	Logging into and Exiting a Privilege Level					6-10
	Controlling Switch Access with TACACS+				6-10
	Understanding TACACS+ 6-10
	TACACS+ Operation	6-12
	Configuring TACACS+	6-13
	Default TACACS+ Configuration			6-13
	Identifying the TACACS+ Server Host and Setting the Authentication Key 6-13
	Configuring TACACS+ Login Authentication					6-14
	Configuring TACACS+ Authorization for Privileged EXEC Access and Network Services								6-16
	Starting TACACS+ Accounting			6-17
	Displaying the TACACS+ Configuration				6-17
	Controlling Switch Access with RADIUS			6-17
	Understanding RADIUS	6-18
	RADIUS Operation 6-19
	Configuring RADIUS	6-19
	Default RADIUS Configuration			6-20
	Identifying the RADIUS Server Host				6-20
	Configuring RADIUS Login Authentication					6-23
	Defining AAA Server Groups		6-24
	Configuring RADIUS Authorization for User Privileged Access and Network Services								6-26
	Starting RADIUS Accounting		6-27
	Configuring Settings for All RADIUS Servers					6-28
	Configuring the Switch to Use Vendor-Specific RADIUS Attributes 6-28
	Configuring the Switch for Vendor-Proprietary RADIUS Server Communication 6-29
	Displaying the RADIUS Configuration				6-30
	Configuring the Switch for Local Authentication and Authorization 6-31
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			Managing the System Time and Date					6-32
			Understanding the System Clock					6-32
			Understanding Network Time Protocol						6-32
			Configuring NTP	6-34
			Default NTP Configuration				6-35
			Configuring NTP Authentication						6-35
			Configuring NTP Associations					6-36
			Configuring NTP Broadcast Service							6-37
			Configuring NTP Access Restrictions							6-38
			Configuring the Source IP Address for NTP Packets										6-40
			Displaying the NTP Configuration						6-41
			Configuring Time and Date Manually						6-41
			Setting the System Clock				6-42
			Displaying the Time and Date Configuration									6-42
			Configuring the Time Zone					6-43
			Configuring Summer Time (Daylight Saving Time)										6-44
			Configuring a System Name and Prompt						6-46
			Default System Name and Prompt Configuration									6-46
			Configuring a System Name			6-46
			Configuring a System Prompt			6-47
			Understanding DNS		6-47
			Default DNS Configuration					6-48
			Setting Up DNS		6-48
			Displaying the DNS Configuration						6-49
			Creating a Banner	6-49
			Default Banner Configuration			6-49
			Configuring a Message-of-the-Day Login Banner									6-50
			Configuring a Login Banner			6-51
			Managing the MAC Address Table				6-51
			Building the Address Table			6-52
			MAC Addresses and VLANs			6-52
			Default MAC Address Table Configuration								6-53
			Changing the Address Aging Time					6-53
			Removing Dynamic Address Entries						6-54
			Configuring MAC Address Notification Traps								6-54
			Adding and Removing Static Address Entries								6-56
			Displaying Address Table Entries					6-57
			Optimizing System Resources for User-Selected Features										6-57
			Using the Templates		6-59
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C H A P T E R 7	Configuring 802.1X Port-Based Authentication	7-1
	Understanding 802.1X Port-Based Authentication	7-1
	Device Roles 7-2
	Authentication Initiation and Message Exchange 7-3
	Ports in Authorized and Unauthorized States	7-4
	Supported Topologies 7-4

Configuring 802.1X Authentication		7-5
Default 802.1X Configuration 7-6
802.1X Configuration Guidelines		7-7
Enabling 802.1X Authentication		7-8
Configuring the Switch-to-RADIUS-Server Communication			7-9
Enabling Periodic Re-Authentication 7-10
Manually Re-Authenticating a Client Connected to a Port			7-11
Changing the Quiet Period	7-11
Changing the Switch-to-Client Retransmission Time 7-12
Setting the Switch-to-Client Frame-Retransmission Number			7-13
Enabling Multiple Hosts	7-13

	Resetting the 802.1X Configuration to the Default Values 7-14
	Displaying 802.1X Statistics and Status				7-14
	Configuring Interface Characteristics
C H A P T E R 8					8-1
	Understanding Interface Types			8-1
	Port-Based VLANs		8-2
	Switch Ports	8-2
	Access Ports		8-2
	Trunk Ports		8-3
	EtherChannel Port Groups			8-3
	Switch Virtual Interfaces			8-4
	Routed Ports	8-4
	Connecting Interfaces 8-5
	Using the Interface Command			8-6
	Procedures for Configuring Interfaces 8-7
	Configuring a Range of Interfaces				8-9
	Configuring and Using Interface Range Macros					8-11
	Configuring Layer 2 Interfaces			8-12
	Default Layer 2 Ethernet Interface Configuration					8-13
	Configuring Interface Speed and Duplex Mode					8-14

	Configuration Guidelines	8-14
	Setting the Interface Speed and Duplex Parameters 8-14
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	Configuring IEEE 802.3X Flow Control					8-16
	Adding a Description for an Interface					8-17
	Monitoring and Maintaining the Layer 2 Interface						8-18
	Monitoring Interface and Controller Status						8-18
	Clearing and Resetting Interfaces and Counters 8-20
	Shutting Down and Restarting the Interface						8-21
	Configuring Layer 3 Interfaces 8-22
	Creating and Maintaining VLANs
C H A P T E R 9				9-1
	Understanding VLANs		9-1
	Number of Supported VLANs			9-2
	VLAN Port Membership Modes				9-3
	Using the VLAN Trunking Protocol			9-3
	The VTP Domain and VTP Modes				9-4
	VTP Advertisements		9-5
	VTP Version 2	9-6
	VTP Pruning	9-6

			Configuring VTP 9-8
			Default VTP Configuration			9-8
			VTP Configuration Guidelines				9-8
			Configuring a VTP Server			9-10
			Configuring a VTP Client			9-11
			Disabling VTP (VTP Transparent Mode)						9-11
			Enabling VTP Version 2			9-12
			Enabling VTP Pruning		9-13
			Monitoring VTP	9-13
			VLANs in the VTP Database		9-15
			Token Ring VLANs	9-15
			Default VLAN Configuration			9-15
			VLAN Configuration Guidelines				9-16
			Configuring VLANs in the VTP Database					9-17
			Adding an Ethernet VLAN			9-17
			Modifying an Ethernet VLAN				9-18
			Deleting a VLAN from the Database					9-18
			Assigning Static-Access Ports to a VLAN						9-19
			Displaying VLANs in the VTP Database						9-21
			Understanding VLAN Trunks		9-22
			Trunking Overview	9-22
			Encapsulation Types	9-23
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802.1Q Configuration Considerations		9-24
Default Layer 2 Ethernet Interface VLAN Configuration					9-24
Configuring an Ethernet Interface as a Trunk Port				9-25
Configuring a Trunk Port 9-25
Defining the Allowed VLANs on a Trunk			9-27
Changing the Pruning-Eligible List		9-28
Configuring the Native VLAN for Untagged Traffic					9-29
Load Sharing Using STP 9-29
Load Sharing Using STP Port Priorities			9-30
Configuring STP Port Priorities and Load Sharing					9-30
Load Sharing Using STP Path Cost	9-32
Configuring STP Path Costs and Load Sharing				9-32
Understanding VMPS 9-33
Dynamic Port VLAN Membership	9-34
VMPS Database Configuration File	9-34
VMPS Configuration Guidelines	9-36

		Default VMPS Configuration				9-37
		Configuring an Interface as a Layer 2 Dynamic Access Port							9-37
		Entering the IP Address of the VMPS					9-37
		Configuring Dynamic Access Ports on VMPS Clients							9-38
		Reconfirming VLAN Memberships 9-39
		Changing the Reconfirmation Interval					9-39
		Changing the Retry Count				9-39
		Administering and Monitoring the VMPS					9-40
		Troubleshooting Dynamic Port VLAN Membership						9-40
		Dynamic Port VLAN Membership Configuration Example							9-40
		Configuring STP
C H A P T E R 10			10-1
		Understanding Basic STP Features				10-1
		Supported STP Instances 10-2
		STP Overview 10-2
		Bridge ID, Switch Priority, and Extended System ID						10-3
		Election of the Root Switch				10-3
		Bridge Protocol Data Units			10-4
		STP Timers	10-5
		Creating the STP Topology			10-5
		STP Interface States		10-6
		Blocking State		10-7
		Listening State		10-7
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			Learning State		10-7
			Forwarding State		10-8
			Disabled State		10-8
			STP Address Management				10-8
			STP and IEEE 802.1Q Trunks				10-8
			VLAN-Bridge STP	10-9
			STP and Redundant Connectivity					10-9
			Accelerated Aging to Retain Connectivity							10-10
			Understanding Advanced STP Features						10-10
			Understanding Port Fast			10-10
			Understanding BPDU Guard				10-11
			Understanding UplinkFast			10-12
			Understanding Cross-Stack UplinkFast 10-13
			How CSUF Works		10-14
			Events that Cause Fast Convergence							10-15
			Limitations	10-16
			Connecting the Stack Ports					10-16
			Understanding BackboneFast				10-18
			Understanding Root Guard				10-20
			Understanding EtherChannel Guard						10-20
			Configuring Basic STP Features				10-21
			Default STP Configuration				10-21
			Disabling STP 10-22
			Configuring the Root Switch				10-22
			Configuring a Secondary Root Switch						10-24
			Configuring STP Port Priority				10-26
			Configuring STP Path Cost				10-27
			Configuring the Switch Priority of a VLAN							10-28
			Configuring the Hello Time				10-29
			Configuring the Forwarding-Delay Time for a VLAN								10-29
			Configuring the Maximum-Aging Time for a VLAN								10-30
			Configuring STP for Use in a Cascaded Stack 10-30
			Displaying STP Status		10-31
			Configuring Advanced STP Features					10-32
			Configuring Port Fast		10-32
			Configuring BPDU Guard			10-33
			Configuring UplinkFast for Use with Redundant Links								10-34
			Configuring Cross-Stack UplinkFast						10-35
			Configuring BackboneFast				10-36
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		Configuring Root Guard	10-36
		Enabling EtherChannel Guard			10-37
		Configuring IGMP Snooping and MVR
C H A P T E R 11						11-1
		Understanding IGMP Snooping		11-1
		Joining a Multicast Group		11-2
		Leaving a Multicast Group		11-4
		Immediate-Leave Processing			11-4
		Configuring IGMP Snooping	11-5
		Default IGMP Snooping Configuration					11-5
		Enabling or Disabling IGMP Snooping					11-5
		Setting the Snooping Method			11-6
		Configuring a Multicast Router Port					11-7
		Configuring a Host Statically to Join a Group							11-8
		Enabling IGMP Immediate-Leave Processing							11-9
		Displaying IGMP Snooping Information				11-9
		Understanding Multicast VLAN Registration						11-12
		Using MVR in a Multicast Television Application 11-12
		Configuring MVR 11-14
		Configuration Guidelines and Limitations						11-14
		Default MVR Configuration		11-15
		Configuring MVR Global Parameters					11-15
		Configuring MVR Interfaces		11-16
		Displaying MVR Information	11-18
		Configuring IGMP Filtering	11-20
		Default IGMP Filtering Configuration					11-20
		Configuring IGMP Profiles		11-20
		Applying IGMP Profiles	11-22
		Setting the Maximum Number of IGMP Groups							11-23
		Displaying IGMP Filtering Configuration					11-24
		Configuring Port-Based Traffic Control
C H A P T E R 12						12-1
		Configuring Storm Control	12-1
		Understanding Storm Control			12-1
		Default Storm Control Configuration					12-3
		Enabling Storm Control	12-3
		Disabling Storm Control	12-4
		Configuring Protected Ports	12-5
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	Configuring Port Blocking				12-6
	Blocking Flooded Traffic on an Interface								12-6
	Resuming Normal Forwarding on a Port								12-7
	Configuring Port Security				12-8
	Understanding Port Security						12-8
	Default Port Security Configuration							12-9
	Configuration Guidelines					12-9
	Enabling and Configuring Port Security								12-9
	Displaying Port-Based Traffic Control Settings								12-11
	Configuring CDP
C H A P T E R 13		13-1
	Understanding CDP		13-1
	Configuring CDP	13-2
	Default CDP Configuration					13-2
	Configuring the CDP Characteristics							13-2
	Disabling and Enabling CDP						13-3
	Disabling and Enabling CDP on an Interface									13-4
	Monitoring and Maintaining CDP						13-5
	Configuring UDLD
C H A P T E R 14		14-1
	Understanding UDLD			14-1
	Configuring UDLD		14-3
	Default UDLD Configuration						14-3
	Enabling UDLD Globally					14-3
	Enabling UDLD on an Interface						14-4
	Resetting an Interface Shut Down by UDLD									14-4
	Displaying UDLD Status				14-5
	Configuring SPAN
C H A P T E R 15		15-1
	Understanding SPAN			15-1
	SPAN Concepts and Terminology							15-2
	SPAN Session				15-2
	Traffic Types			15-3
	Source Port			15-4
	Destination Port				15-4
	VLAN-Based SPAN					15-5
	SPAN Traffic			15-5

			SPAN Interaction with Other Features	15-5
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	Configuring SPAN	15-6
	Default SPAN Configuration			15-7
	SPAN Configuration Guidelines				15-7
	Creating a SPAN Session and Specifying Ports to Monitor							15-8
	Removing Ports from a SPAN Session					15-10
	Specifying VLANs to Monitor			15-11
	Specifying VLANs to Filter			15-12
	Displaying SPAN Status		15-13
	Configuring RMON
C H A P T E R 16		16-1
	Understanding RMON		16-1
	Configuring RMON	16-2
	Default RMON Configuration			16-3
	Configuring RMON Alarms and Events					16-3
	Configuring RMON Collection on an Interface 16-5
	Displaying RMON Status		16-6
	Configuring System Message Logging
C H A P T E R 17					17-1
	Understanding System Message Logging					17-1
	Configuring System Message Logging				17-2
	System Log Message Format			17-2
	Default System Message Logging Configuration						17-3
	Disabling and Enabling Message Logging 17-4
	Setting the Message Display Destination Device						17-4
	Synchronizing Log Messages			17-6
	Enabling and Disabling Timestamps on Log Messages 17-7
	Enabling and Disabling Sequence Numbers in Log Messages							17-8
	Defining the Message Severity Level					17-8

Limiting Syslog Messages Sent to the History Table and to SNMP 17-10

Configuring UNIX Syslog Servers	17-10
Logging Messages to a UNIX Syslog Daemon		17-11
Configuring the UNIX System Logging Facility		17-11
Displaying the Logging Configuration	17-12

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C H A P T E R 18	Configuring SNMP 18-1
	Understanding SNMP	18-1
	SNMP Versions	18-2
	SNMP Manager Functions				18-2
	SNMP Agent Functions			18-3
	SNMP Community Strings				18-3
	Using SNMP to Access MIB Variables					18-3
	Configuring SNMP	18-4
	Default SNMP Configuration				18-4
	Disabling the SNMP Agent				18-5
	Configuring Community Strings 18-5
	Configuring Trap Managers and Enabling Traps							18-7
	Setting the Agent Contact and Location Information								18-9
	Limiting TFTP Servers Used Through SNMP						18-9
	SNMP Examples	18-10
	Displaying SNMP Status		18-10
	Configuring Network Security with ACLs
C H A P T E R 19						19-1
	Understanding ACLs	19-1
	Supported ACLs	19-2
	Router ACLs	19-2
	VLAN Maps	19-3
	Handling Fragmented and Unfragmented Traffic							19-4
	Configuring Router ACLs		19-5
	Hardware and Software Handling of Router ACLs								19-5
	Unsupported Features		19-6
	Creating Standard and Extended IP ACLs						19-6
	Access List Numbers			19-7
	Creating a Numbered Standard ACL						19-8
	Creating a Numbered Extended ACL						19-9
	Creating Named Standard and Extended ACLs								19-14
	Applying Time Ranges to ACLs					19-15
	Including Comments About Entries in ACLs							19-18
	Applying the ACL to an Interface or Terminal Line								19-18
	Displaying ACLs and Access Groups					19-20
	ACL Configuration Examples				19-22
	Numbered ACLs		19-24
	Extended ACLs		19-24

			Named ACLs	19-24
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Time Range Applied to an IP ACL 19-25

Commented IP ACL Entries 19-25

ACL Logging 19-26

Configuring VLAN Maps	19-27
VLAN Map Configuration Guidelines		19-28
Creating Named MAC Extended ACLs		19-28
Creating a VLAN Map	19-30

	Examples of ACLs and VLAN Maps					19-30
	Applying a VLAN Map to a VLAN				19-32
	Displaying VLAN Map Information				19-33
	Using VLAN Maps in Your Network				19-33
	Wiring Closet Configuration				19-34
	Denying Access to a Server on Another VLAN 19-35
	Using VLAN Maps with Router ACLs			19-36
	Guidelines	19-36
	Determining if the ACL Configuration Fits in Hardware 19-37
	Examples of Router ACLs and VLAN Maps Applied to VLANs						19-39
	ACLs and Switched Packets				19-39
	ACLs and Bridged Packets			19-40
	ACLs and Routed Packets			19-41
	ACLs and Multicast Packets				19-42
	Configuring QoS
C H A P T E R 20		20-1
	Understanding QoS		20-1
	Basic QoS Model		20-3
	Classification 20-4
	Classification Based on QoS ACLs					20-7
	Classification Based on Class Maps and Policy Maps						20-7
	Policing and Marking 20-8
	Mapping Tables		20-11

	Queueing and Scheduling		20-12
	Queueing and Scheduling on Gigabit-Capable Ports			20-12
	Queueing and Scheduling on 10/100 Ethernet Ports			20-15
	Packet Modification	20-17
	Configuring QoS 20-18
	Default QoS Configuration		20-18
	Configuration Guidelines		20-20
	Enabling QoS Globally	20-21
	Configuring Classification Using Port Trust States 20-21
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Configuring the Trust State on Ports within the QoS Domain 20-22
Configuring the CoS Value for an Interface			20-24
Configuring the DSCP Trust State on a Port Bordering Another QoS Domain 20-25
Configuring a QoS Policy	20-26
Classifying Traffic by Using ACLs		20-27
Classifying Traffic by Using Class Maps 20-30
Classifying, Policing, and Marking Traffic by Using Policy Maps 20-32
Classifying, Policing, and Marking Traffic by Using Aggregate Policers 20-37
Configuring DSCP Maps	20-39
Configuring the CoS-to-DSCP Map		20-39
Configuring the IP-Precedence-to-DSCP Map			20-40
Configuring the Policed-DSCP Map		20-41
Configuring the DSCP-to-CoS Map		20-42

					Configuring the DSCP-to-DSCP-Mutation Map						20-43
					Configuring Egress Queues on Gigabit-Capable Ethernet Ports 20-44
					Mapping CoS Values to Select Egress Queues						20-45
					Configuring the Egress Queue Size Ratios				20-46
					Configuring Tail-Drop Threshold Percentages					20-47
					Configuring WRED Drop Thresholds Percentages						20-48
					Configuring the Egress Expedite Queue				20-50
					Allocating Bandwidth among Egress Queues					20-50
					Configuring Egress Queues on 10/100 Ethernet Ports						20-51
					Mapping CoS Values to Select Egress Queues						20-52
					Configuring the Minimum-Reserve Levels				20-53
					Configuring the Egress Expedite Queue				20-54
					Allocating Bandwidth among Egress Queues					20-54
					Displaying QoS Information		20-56
					QoS Configuration Examples		20-56
					QoS Configuration for the Common Wiring Closet					20-57
					QoS Configuration for the Intelligent Wiring Closet						20-58
					QoS Configuration for the Distribution Layer				20-59
					Configuring EtherChannel
C H A P T E R 21						21-1
					Understanding EtherChannel		21-1
					Understanding Port-Channel Interfaces			21-2
					Understanding the Port Aggregation Protocol				21-3
					PAgP Modes	21-4
					Physical Learners and Aggregate-Port Learners						21-5
					PAgP Interaction with Other Features			21-5
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Understanding Load Balancing and Forwarding Methods 21-5
Configuring EtherChannel 21-7
Default EtherChannel Configuration	21-7
EtherChannel Configuration Guidelines 21-8
Configuring Layer 2 EtherChannels	21-9
Configuring Layer 3 EtherChannels	21-11

		Creating Port-Channel Logical Interfaces 21-11
		Configuring the Physical Interfaces						21-12
		Configuring EtherChannel Load Balancing							21-13
		Configuring the PAgP Learn Method and Priority								21-14
		Displaying EtherChannel and PAgP Status						21-16
		Configuring IP Unicast Routing
C H A P T E R 22						22-1
		Understanding Routing		22-2
		Steps for Configuring Routing				22-3
		Configuring IP Addressing			22-4
		Default Addressing Configuration					22-4
		Assigning IP Addresses to Network Interfaces								22-5
		Use of Subnet Zero			22-8
		Classless Routing			22-8
		Configuring Address Resolution Methods							22-10
		Define a Static ARP Cache					22-11
		Set ARP Encapsulation				22-12
		Enable Proxy ARP			22-13
		Routing Assistance When IP Routing is Disabled								22-14
		Proxy ARP	22-14
		Default Gateway			22-15
		ICMP Router Discovery Protocol (IRDP)							22-15
		Configuring Broadcast Packet Handling						22-17
		Enabling Directed Broadcast-to-Physical Broadcast Translation 22-17
		Forwarding UDP Broadcast Packets and Protocols 22-18
		Establishing an IP Broadcast Address							22-20
		Flooding IP Broadcasts				22-20
		Monitoring and Maintaining IP Addressing							22-21
		Enabling IP Routing	22-24
		Configuring RIP 22-25
		RIP Authentication		22-28
		Summary Addresses and Split Horizon						22-28
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Configuring IGRP	22-30
Load Balancing and Traffic Distribution Control 22-31
Split Horizon	22-34
Configuring OSPF	22-35
OSPF Interface Parameters			22-38
OSPF Area Parameters 22-39
Other OSPF Behavior Parameters				22-41
Change LSA Group Pacing			22-43
Loopback Interface		22-43
Monitoring OSPF		22-44
Configuring EIGRP	22-46
EIGRP Router Mode Commands 22-48
EIGRP Interface Mode Commands				22-49
Configure EIGRP Route Authentication 22-50
Monitoring and Maintaining EIGRP				22-51
Configuring Protocol-Independent Features					22-53
Configuring Cisco Express Forwarding					22-53
Configuring the Number of Equal-Cost Routing Paths 22-54
Configuring Static Routes			22-55
Specifying Default Routes			22-56
Specifying a Default Network				22-56
Redistributing Routing Information				22-57
Filtering Routing Information			22-61

	Setting Passive Interfaces		22-61
	Controlling Advertising and Processing in Routing Updates 22-62
	Filtering Sources of Routing Information 22-62
	Managing Authentication Keys		22-63
	Monitoring and Maintaining the IP Network 22-64
	Configuring HSRP
C H A P T E R 23		23-1
	Understanding HSRP 23-1
	Configuring HSRP	23-3

Default HSRP Configuration 23-4

Enabling HSRP 23-4

Configuring HSRP Group Attributes 23-6

Configuring HSRP Priority 23-6

			Configuring HSRP Authentication and Timers	23-8
			Configuring HSRP Groups and Clustering 23-9
			Displaying HSRP Configurations 23-10
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C H A P T E R 24		Configuring IP Multicast Routing			24-1
		Cisco Implementation of IP Multicast Routing						24-2
		Understanding IGMP		24-3
		IGMP Version 1		24-3
		IGMP Version 2		24-4
		Understanding PIM	24-5
		PIM Versions	24-5
		PIM Modes 24-5
		Auto-RP 24-8
		Bootstrap Router		24-8
		Multicast Forwarding and Reverse Path Check								24-9
		Neighbor Discovery 24-10
		Understanding DVMRP		24-11
		DVMRP Neighbor Discovery				24-11
		DVMRP Route Table			24-11
		DVMRP Source Distribution Tree					24-11
		Understanding CGMP		24-11
		Joining a Group with CGMP				24-12
		Leaving a Group with CGMP				24-13
		Configuring IP Multicast Routing			24-13
		Default Multicast Routing Configuration						24-13
		Multicast Routing Configuration Guidelines							24-14
		PIMv1 and PIMv2 Interoperability						24-14
		Auto-RP and BSR Configuration Guidelines 24-15
		Configuring Basic Multicast Routing					24-15
		Configuring a Rendezvous Point				24-17
		Manually Assigning an RP to Multicast Groups								24-17
		Configuring Auto-RP			24-18
		Configuring PIMv2 BSR			24-22
		Using Auto-RP and a BSR			24-27
		Monitoring the RP Mapping Information						24-27
		Troubleshooting PIMv1 and PIMv2 Interoperability Problems 24-28
		Configuring Advanced PIM Features				24-28
		Understanding PIM Shared Tree and Source Tree								24-28
		Delaying the Use of PIM Shortest-Path Tree							24-29
		Modifying the PIM Router-Query Message Interval								24-30
		Configuring Optional IGMP Features				24-31
		Default IGMP Configuration			24-31
		Changing the IGMP Version			24-32
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					Changing the IGMP Query Timeout for IGMPv2						24-32
					Changing the Maximum Query Response Time for IGMPv2								24-33
					Configuring the Multilayer Switch as a Member of a Group								24-34
					Controlling Access to IP Multicast Groups					24-35
					Modifying the IGMP Host-Query Message Interval							24-36
					Configuring the Multilayer Switch as a Statically Connected Member 24-36
					Configuring Optional Multicast Routing Features						24-37
					Enabling CGMP Server Support			24-38
					Configuring sdr Listener Support			24-39
					Enabling sdr Listener Support			24-39
					Limiting How Long an sdr Cache Entry Exists							24-39
					Configuring the TTL Threshold		24-40
					Configuring an IP Multicast Boundary				24-42
					Configuring Basic DVMRP Interoperability Features						24-43
					Configuring DVMRP Interoperability 24-44
					Controlling Unicast Route Advertisements					24-44
					Configuring a DVMRP Tunnel		24-46
					Advertising Network 0.0.0.0 to DVMRP Neighbors							24-48
					Responding to mrinfo Requests			24-49
					Configuring Advanced DVMRP Interoperability Features							24-50
					Enabling DVMRP Unicast Routing			24-50
					Rejecting a DVMRP Nonpruning Neighbor					24-51
					Controlling Route Exchanges		24-53
					Limiting the Number of DVMRP Routes Advertised 24-53
					Changing the DVMRP Route Threshold					24-54
					Configuring a DVMRP Summary Address						24-54
					Disabling DVMRP Autosummarization					24-56
					Adding a Metric Offset to the DVMRP Route							24-56
					Monitoring and Maintaining IP Multicast Routing						24-57
					Clearing Caches, Tables, and Databases				24-58
					Displaying System and Network Statistics					24-58
					Monitoring IP Multicast Routing			24-59
					Configuring MSDP 25-1
C H A P T E R 25
					Understanding MSDP	25-1
					MSDP Operation	25-2
					MSDP Benefits	25-3
					Configuring MSDP	25-4
					Default MSDP Configuration		25-4
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Configuring a Default MSDP Peer		25-4
Caching Source-Active State	25-6
Requesting Source Information from an MSDP Peer 25-8
Controlling Source Information that Your Switch Originates			25-8
Redistributing Sources	25-9
Filtering Source-Active Request Messages 25-11
Controlling Source Information that Your Switch Forwards			25-12
Using a Filter 25-12
Using TTL to Limit the Multicast Data Sent in SA Messages 25-14
Controlling Source Information that Your Switch Receives			25-14
Configuring an MSDP Mesh Group		25-16
Shutting Down an MSDP Peer	25-16

	Including a Bordering PIM Dense-Mode Region in MSDP 25-17
	Configuring an Originating Address other than the RP Address				25-18
	Monitoring and Maintaining MSDP		25-19
	Configuring Fallback Bridging
C H A P T E R 26		26-1
	Understanding Fallback Bridging		26-1
	Configuring Fallback Bridging	26-3
	Default Fallback Bridging Configuration			26-3
	Creating a Bridge Group	26-4
	Preventing the Forwarding of Dynamically Learned Stations				26-5
	Configuring the Bridge Table Aging Time			26-6
	Filtering Frames by a Specific MAC Address 26-6
	Adjusting Spanning-Tree Parameters 26-7

Changing the Switch Priority	26-8
Changing the Interface Priority	26-8
Assigning a Path Cost 26-9
Adjusting BPDU Intervals 26-10

		Disabling the Spanning Tree on an Interface		26-12
		Monitoring and Maintaining the Network	26-12
		Troubleshooting 27-1
C H A P T E R 27
		Using Recovery Procedures 27-1
		Recovering from Corrupted Software	27-2
		Recovering from a Lost or Forgotten Password		27-3
		Password Recovery with Password Recovery Enabled 27-3
		Procedure with Password Recovery Disabled		27-5
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		Recovering from a Command Switch Failure					27-7
		Replacing a Failed Command Switch with a Cluster Member						27-7
		Replacing a Failed Command Switch with Another Switch						27-9
		Recovering from Lost Member Connectivity					27-10
		Preventing Autonegotiation Mismatches				27-10
		Diagnosing Connectivity Problems			27-11
		Understanding Ping		27-11
		Executing Ping	27-11
		Understanding IP Traceroute			27-12
		Executing IP Traceroute 27-13
		Using Debug Commands		27-14
		Enabling Debugging on a Specific Feature					27-14
		Enabling All-System Diagnostics 27-15
		Redirecting Debug and Error Message Output 27-15
		Using the show forward Command			27-15
		Using the crashinfo File		27-17
		Supported MIBs A-1
A P P E N D I X	A
		MIB List A-1
		Using FTP to Access the MIB Files			A-2
		Working with the IOS File System, Configuration Files, and Software Images B-1
A P P E N D I X	B
		Working with the Flash File System			B-1
		Displaying Available File Systems				B-2
		Setting the Default File System			B-3
		Displaying Information about Files on a File System B-3
		Changing Directories and Displaying the Working Directory B-3
		Creating and Removing Directories				B-4
		Copying Files	B-4
		Deleting Files	B-5

Creating, Displaying, and Extracting tar Files

B-6

Creating a tar File	B-6
Displaying the Contents of a tar File B-6
Extracting a tar File	B-7
Displaying the Contents of a File B-8

			Working with Configuration Files B-8
			Guidelines for Creating and Using Configuration Files	B-9
			Configuration File Types and Location B-9
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Creating a Configuration File By Using a Text Editor

B-10

Copying Configuration Files By Using TFTP

B-10

Preparing to Download or Upload a Configuration File By Using TFTP

B-10

Downloading the Configuration File By Using TFTP B-11

Uploading the Configuration File By Using TFTP

B-12

Copying Configuration Files By Using FTP

B-12

Preparing to Download or Upload a Configuration File By Using FTP

B-13

Downloading a Configuration File By Using FTP

B-13

Uploading a Configuration File By Using FTP

B-15

Copying Configuration Files By Using RCP

B-16

Preparing to Download or Upload a Configuration File By Using RCP

B-16

Downloading a Configuration File By Using RCP

B-17

Uploading a Configuration File By Using RCP

B-18

Clearing Configuration Information

B-19

Clearing the Startup Configuration File

B-19

Deleting a Stored Configuration File

B-19

Working with Software Images

B-19

Image Location on the Switch

B-20

tar File Format of Images on a Server or Cisco.com

B-20

Copying Image Files By Using TFTP

B-21

Preparing to Download or Upload an Image File By Using TFTP

B-22

Downloading an Image File By Using TFTP

B-22

Uploading an Image File By Using TFTP

B-24

Copying Image Files By Using FTP

B-25

Preparing to Download or Upload an Image File By Using FTP

B-25

Downloading an Image File By Using FTP

B-26

Uploading an Image File By Using FTP

B-28

Copying Image Files By Using RCP

B-29

Preparing to Download or Upload an Image File By Using RCP

B-29

Downloading an Image File By Using RCP

B-30

Uploading an Image File By Using RCP

B-32

Unsupported CLI Commands C-1

A P P E N D I X C

Access Control Lists C-1

Unsupported Privileged EXEC Commands

C-1

ARP Commands C-1

Unsupported Global Configuration Commands

C-1

Unsupported Interface Configuration Commands

C-1

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FallBack Bridging		C-2
Unsupported Privileged EXEC Commands			C-2
Unsupported Global Configuration Commands				C-2
Unsupported Interface Configuration Commands				C-2
HSRP	C-3
Unsupported Global Configuration Commands				C-3
Unsupported Interface Configuration Commands				C-3
Interface Configuration Commands C-4
IP Multicast Routing		C-4
Unsupported Privileged EXEC Commands			C-4
Unsupported Global Configuration Commands				C-4
Unsupported Interface Configuration Commands				C-5
IP Unicast Routing		C-5
Unsupported Privileged EXEC or User EXEC Commands C-5
Unsupported Global Configuration Commands				C-5
Unsupported Interface Configuration Commands				C-6
Unsupported VPN Configuration Commands			C-6
Unsupported VRF Configuration Commands			C-6
Unsupported Route Map Commands C-6
MSDP	C-7
Unsupported Privileged EXEC Commands			C-7
Unsupported Global Configuration Commands				C-7
RADIUS	C-7
Unsupported Global Configuration Commands				C-7

I N D E X

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Preface

Audience

This guide is for the networking professional managing the Catalyst 3550 switch, hereafter referred to as the switch or the multilayer switch. Before using this guide, you should have experience working with the Cisco IOS and be familiar with the concepts and terminology of Ethernet and local area networking.

Purpose

This guide provides the information you need to configure Layer 2 and Layer 3 software features on your switch. The Catalyst 3550 switch is supported by either the standard multilayer software image (SMI) or the enhanced multilayer software image (EMI). The EMI provides a richer set of enterprise-class features, including hardware-based IP unicast and multicast routing, inter-VLAN routing, routed access control lists (ACLs), and the Hot Standby Router Protocol (HSRP). All Catalyst 3550 Gigabit Ethernet switches are shipped with the EMI pre-installed. Catalyst 3550 Fast Ethernet switches are shipped with either the SMI or the EMI pre-installed. After initial deployment, you can order the Enhanced Multilayer Software Image Upgrade kit to upgrade Catalyst 3550 Fast Ethernet switches from running the SMI to the EMI.

This guide provides procedures for using the commands that have been created or changed for use with the Catalyst 3550 switch. It does not provide detailed information about these commands. For detailed information about these commands, refer to the Catalyst 3550 Multilayer Switch Command Reference for this release. For information about the standard IOS Release 12.1 commands, refer to the IOS documentation set available from the Cisco.com home page at Service and Support > Technical Documents. On the Cisco Product Documentation home page, select Release 12.1 from the Cisco IOS Software drop-down list.

This guide also includes an overview of the Cluster Management Suite (CMS) web-based, switch management interface, which helps you create and manage clusters of switches. This guide does not provide field-level descriptions of the CMS windows nor does it provide the procedures for configuring switches and switch clusters from CMS. For all CMS window descriptions and procedures, refer to the CMS online help, which is integrated with the software image.

This guide does not describe system messages you might encounter or how to install your switch. For more information, refer to the Catalyst 3550 Multilayer Switch System Message Guide for this release and to the Catalyst 3550 Multilayer Switch Hardware Installation Guide.

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Preface

Organization

Organization

This guide is organized into these chapters:

Chapter 1, “Overview,” lists the software features of this release and provides examples of how the switch can be deployed in a network.

Chapter 2, “Using the Command-Line Interface,” describes how to access the command modes, use the command-line interface (CLI), and describes CLI messages that you might receive. It also describes how to get help, abbreviate commands, use no and default forms of commands, use command history and editing features, and how to search and filter the output of show and more commands.

Chapter 3, “Getting Started with CMS,” describes the Cluster Management Suite (CMS) web-based, switch management interface. For information on configuring your web browser and accessing CMS, refer to the release notes. For field-level descriptions of all CMS windows and procedures for using the CMS windows, refer to the online help.

Chapter 4, “Assigning the Switch IP Address and Default Gateway,” describes how to create the initial switch configuration (for example, assign the switch IP address and default gateway information) by using a variety of automatic and manual methods. It also describes how to modify the switch startup configuration.

Chapter 5, “Clustering Switches,” describes switch clusters and the considerations for creating and maintaining them. The online help provides the CMS procedures for configuring switch clusters. Configuring switch clusters is most easily performed through CMS; therefore, CLI procedures are not provided. Cluster commands are described in the Catalyst 3550 Multilayer Switch Command Reference.

Chapter 6, “Administering the Switch,” describes how to perform one-time operations to administer your switch. It describes how to prevent unauthorized access to your switch through the use of passwords, privilege levels, the Terminal Access Controller Access Control System Plus (TACACS+), and the Remote Authentication Dial-In User Service (RADIUS). It also describes how to set the system date and time, system name and prompt, create a login banner, how to manage the MAC address table, and how to optimize system resources for user-selected features.

Chapter 7, “Configuring 802.1X Port-Based Authentication,” describes how to configure 802.1X port-based authentication to prevent unauthorized devices (clients) from gaining access to the network. As LANs extend to hotels, airports, and corporate lobbies, insecure environments could be created.

Chapter 8, “Configuring Interface Characteristics,” defines the types of Layer 2 and Layer 3 interfaces on the switch. It describes the interface command and provides procedures for configuring physical interfaces.

Chapter 9, “Creating and Maintaining VLANs,” describes how to create and maintain VLANs. It includes information about VLAN modes, the VLAN Trunking Protocol (VTP) database, and the VLAN Membership Policy Server (VMPS).

Chapter 10, “Configuring STP,” describes how to configure basic and advanced spanning-tree features.

Chapter 11, “Configuring IGMP Snooping and MVR,” describes how to configure Layer 2 Internet Group Management Protocol (IGMP) snooping. It also describes Multicast VLAN Registration (MVR), a local IGMP snooping feature available on the switch, and how to use IGMP filtering to control multicast group membership.

Chapter 12, “Configuring Port-Based Traffic Control,” describes how to reduce traffic storms by setting broadcast, multicast, and unicast storm-control threshold levels; how to protect ports from receiving traffic from other ports on a switch; how to block unknown broadcast and unicast traffic; and how to configure port security using secure MAC addresses.

Chapter 13, “Configuring CDP,” describes how to configure Cisco Discovery Protocol (CDP) on your switch.

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Preface

Organization

Chapter 14, “Configuring UDLD,” describes how to configure the UniDirectional Link Detection (UDLD) feature. UDLD enables devices connected through fiber-optic or twisted-pair Ethernet cables to monitor the physical configuration of the cables and detect when a unidirectional link exists.

Chapter 15, “Configuring SPAN,” describes how to configure Switch Port Analyzer (SPAN), which selects network traffic for analysis by a network analyzer such as a SwitchProbe device or other Remote Monitoring (RMON) probe. SPAN mirrors traffic received or sent (or both) on a source port, or traffic received on one or more source ports or source VLANs, to a destination port.

Chapter 16, “Configuring RMON,” describes how to configure remote monitoring (RMON). The RMON feature, which is used with the Simple Network Management Protocol (SNMP) agent in the switch, means that you can monitor all the traffic flowing among switches on all connected LAN segments.

Chapter 17, “Configuring System Message Logging,” describes how to configure system message logging. It describes the message format, how to change the message display destination device, limit the type of messages sent, configure UNIX server syslog daemon and define the UNIX system logging facility, and timestamp messages.

Chapter 18, “Configuring SNMP,” describes how to configure the Simple Network Management Protocol (SNMP). It describes how to configure community strings, enable trap managers and traps, set the agent contact and location information, and how to limit TFTP servers used through SNMP.

Chapter 19, “Configuring Network Security with ACLs,” describes how to configure network security on your switch using two types of access control lists (ACLs), router ACLs and VLAN maps. It describes how to apply ACLs to interfaces and provides examples.

Chapter 20, “Configuring QoS,” describes how to configure quality of service (QoS) on your switch. With this feature, you can provide preferential treatment to certain types traffic.

Chapter 21, “Configuring EtherChannel,” describes how to bundle a set of individual ports into a single logical link on Layer 2 and Layer 3 interfaces.

Chapter 22, “Configuring IP Unicast Routing,” describes how to configuring IP unicast routing on your switch, including configuring IP addressing features, Routing Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF) protocol, and Enhanced IGRP (EIGRP). To use this feature, you must have the enhanced multilayer software image installed on your switch.

Chapter 23, “Configuring HSRP,” describes how to use Hot Standby Router Protocol (HSRP) to provide routing redundancy for routing IP traffic without depending on the availability of any single router. To use this feature, you must have the enhanced multilayer software image installed on your switch.

Chapter 24, “Configuring IP Multicast Routing,” how to configuring IP multicast routing. It describes how to use and configure the Internet Group Management Protocol (IGMP), Protocol-Independent Multicast (PIM) protocol, Cisco Group Management Protocol (CGMP) server functionality, and how to inter-operate between PIM and Distance Vector Multicast Routing Protocol (DVMRP) domains. To use this feature, you must have the enhanced multilayer software image installed on your switch.

Chapter 25, “Configuring MSDP,” describes how to configure the Multicast Source Discovery Protocol (MSDP), which is a mechanism to connect multiple PIM sparse-mode domains. To use this feature, you must have the enhanced multilayer software image installed on your switch.

Chapter 26, “Configuring Fallback Bridging,” describes how to configure fallback bridging on your switch. With fallback bridging, you can bridge non-IP protocols between VLAN bridge domains and routed ports. To use this feature, you must have the enhanced multilayer software image installed on your switch

Chapter 27, “Troubleshooting,” describes how to identify and resolve software problems related to the IOS software.

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Preface

Conventions

Appendix A, “Supported MIBs,” lists the supported MIBs for this release and how to use FTP to access the MIB files.

Appendix B, “Working with the IOS File System, Configuration Files, and Software Images,” describes how to manipulate the Flash file system, how to copy configuration files, and how to archive (upload and download) software images.

Appendix C, “Unsupported CLI Commands,” lists the unsupported command-line interface (CLI) commands that are displayed when you enter the question mark (?) at the switch prompt. The unsupported commands are listed by software feature and command mode.

Conventions

This publication uses these conventions to convey instructions and information:

Command descriptions use these conventions:

•Commands and keywords are in boldface text.

•Arguments for which you supply values are in italic.

•Square brackets ([ ]) mean optional elements.

•Braces ({ }) group required choices, and vertical bars ( | ) separate the alternative elements.

•Braces and vertical bars within square brackets ([{ | }]) mean a required choice within an optional element.

Interactive examples use these conventions:

•Terminal sessions and system displays are in screen font.

•Information you enter is in boldface screen font.

•Nonprinting characters, such as passwords or tabs, are in angle brackets (< >). Notes, cautions, and timesavers use these conventions and symbols:

Note Means reader take note. Notes contain helpful suggestions or references to materials not contained in this manual.

Caution Means reader be careful. In this situation, you might do something that could result equipment damage or loss of data.

Timesaver Means the following will help you solve a problem. The tips information might not be troubleshooting or even an action, but could be useful information.

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