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38-4

Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX

78-15908-01

Chapter 38 Configuring DNS

Configuring DNS on the Switch

This example shows how to disable DNS on the switch:

Console> (enable) set ip dns disable

DNS is disabled

Console> (enable)

Table of Contents

Default Chapter3
- Table of Contents3
- Related Documentation27
- Obtaining Documentation29
  - Ordering Documentation29
  - Documentation Feedback30
- Obtaining Technical Assistance30
- Obtaining Additional Publications and Information31
- Product Overview33
Chapter 1 Product Overview34
- Catalyst 2948G Switch35
- Catalyst 2948G-GE-TX Switch35
- Catalyst 2980G Switch36
- Supervisor Engine Software36
CHAPTER 2 Using the Command-Line Interface37
- Switch CLI Overview37
- C H a P T E R 2 Using the Command-Line Interface38
- Accessing the Switch CLI38
  - Accessing the CLI through the Console Port38
  - Accessing the CLI through Telnet39
- Switch CLI Command Modes39
- Accessing Help40
- Command-Line Editing41
- History Substitution42
- Abbreviating a Command42
- Completing a Partial Command42
- Scrolling through Command Output42
- Using Command Aliases43
- Specifying Modules, Ports, and Vlans43
- Specifying MAC Addresses44
- Specifying IP Addresses, Host Names, and IP Aliases44
- ROM Monitor CLI45
- Example of a Catalyst 4003 Bootup Display45
CHAPTER 3 Configuring the Switch IP Address and Default Gateway47
- Understanding How the Switch Management Interfaces Work47
- C H a P T E R 3 Configuring the Switch IP Address and Default Gateway48
- Understanding How Automatic IP Configuration Works48
- Preparing to Configure the IP Address and Default Gateway50
- Default IP Address and Default Gateway Configuration51
- Setting the In-Band (Sc0) Interface IP Address51
- Setting the Management Ethernet (Me1) Interface IP Address52
- Configuring Default Gateways53
- Configuring the SLIP (Sl0) Interface on the Console Port54
- Using DHCP or RARP to Obtain an IP Address Configuration56
- Renewing and Releasing a DHCP-Assigned IP Address57
CHAPTER 4 Configuring Ethernet and Fast Ethernet Switching59
- Understanding How Ethernet Works59
- Default Ethernet and Fast Ethernet Configurations60
- Configuring Ethernet and Fast Ethernet Ports61
Chapter 5 Configuring Gigabit Ethernet Switching67
- Understanding How Gigabit Ethernet Works67
- Default Gigabit Ethernet Configuration72
- Configuring Gigabit Ethernet Ports73
CHAPTER 6 Configuring Fast Etherchannel and Gigabit Etherchannel77
- Understanding How Etherchannel Works77
- Pagp and LACP78
- Etherchannel Configuration Guidelines and Restrictions79
- Understanding Pagp81
  - Pagp Modes81
  - Understanding Administrative Groups and Etherchannel Ids82
- Configuring Etherchannel Using Pagp82
- Etherchannel Configuration Examples88
  - Configuration Example of a Four-Port Fast Etherchannel88
  - Configuration Example of a Two-Port Gigabit Etherchannel90
- Understanding LACP92
  - LACP Modes92
  - LACP Parameters93
- Configuring Etherchannel Using LACP94
Chapter 7 Configuring Spanning Tree100
- Understanding How Stps Work100
- Understanding How PVST+ and MISTP Modes Work109
- Understanding How Bridge Identifiers Work111
  - MAC Address Allocation111
  - MAC Address Reduction111
- Understanding How MST Works112
- Understanding How BPDU Skewing Works120
- Using PVST120
- Using Rapid PVST126
- Using MISTP-PVST+ or MISTP128
- Configuring a Root Switch137
- Configuring Spanning Tree Timers142
- Configuring MST144
  - Enabling MST144
  - Mapping and Unmapping Vlans to an MST Instance152
- Configuring Spanning Tree BPDU Skewing155
CHAPTER 8 Configuring Spanning Tree Portfast, BPDU Guard, BPDU Filter, Uplinkfast, Backbonefast, and159
Loop Guard159
- Understanding How Portfast Works160
- Understanding How Portfast BPDU Guard Works160
- Understanding How Portfast BPDU Filtering Works160
- Understanding How Uplinkfast Works161
- Understanding How Backbonefast Works162
- Understanding How Loop Guard Works164
- Configuring Portfast166
- Configuring Portfast BPDU Guard169
  - Enabling Portfast BPDU Guard169
  - Disabling Portfast BPDU Guard170
- Configuring Portfast BPDU Filtering171
  - Enabling Portfast BPDU Filtering171
  - Disabling Portfast BPDU Filtering172
- Configuring Uplinkfast173
  - Enabling Uplinkfast173
  - Disabling Uplinkfast174
- Configuring Backbonefast175
- Configuring Loop Guard176
  - Enabling Loop Guard176
  - Disabling Loop Guard177
- Configuring VTP179
- Understanding How VTP Version 1 and Version 2 Work179
Chapter 9 Configuring VTP180
- Understanding the VTP Domain180
- Understanding VTP Modes180
- Understanding VTP Advertisements181
- Understanding VTP Version 2181
- Understanding VTP Pruning182
- Default VTP Version 1 and Version 2 Configuration183
- VTP Version 1 and Version 2 Configuration Guidelines184
- Configuring VTP Version 1 and Version 2185
- Understanding How VTP Version 3 Works191
- Default VTP Version 3 Configuration200
- Configuring VTP Version 3200
- Understanding How Vlans Work209
Chapter 10 Configuring VLAN210
- VLAN Ranges211
- Configurable VLAN Parameters212
- VLAN Default Configuration212
- VLAN Configuration Guidelines213
- Configuring Vlans on the Switch214
- Configuring Auxiliary Vlans221
  - Understanding Auxiliary Vlans221
- Configuring Private Vlans224
Chapter 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports233
- Understanding How VLAN Trunks Work233
- Default Trunk Configuration237
- Configuring a Trunk Link237
- Disabling VLAN 1 on a Trunk Link240
- Example VLAN Trunk Configurations241
Chapter 12 Configuring Dynamic VLAN Membership with VMPS255
- Understanding How VMPS Works255
- VMPS and Dynamic Port Hardware and Software Requirements256
- Default VMPS and Dynamic Port Configuration256
- Configuration Guidelines for Dynamic Ports and VMPS257
- Configuring VMPS258
- Troubleshooting VMPS and Dynamic Port VLAN Membership264
  - Troubleshooting VMPS265
  - Troubleshooting Dynamic Ports265
- VMPS Example265
- Dynamic Port VLAN Membership with Auxiliary Vlans268
  - Configuration Guidelines268
  - Configuring Dynamic Port VLAN Membership with Auxiliary Vlans268
Chapter 13 Configuring GVRP271
- Understanding How GVRP Works271
- GVRP Hardware and Software Requirements271
- Default GVRP Configuration272
- GVRP Configuration Guidelines272
- Configuring GVRP on the Switch272
Chapter 14 Configuring Qo280
- Understanding Qos Terminology280
- Understanding Classification and Marking at the Ingress Port281
- Understanding Scheduling281
- Software Requirements282
- Qos Default Configuration282
- Configuring Qos on the Switch282
Configuring Qos280
- Understanding How Qos Works280
Chapter 15 Configuring Multicast Services287
- Understanding How Multicasting Works287
- Configuring CGMP290
- Configuring GMRP295
- Configuring Multicast Router Ports and Group Entries301
- Filtering IGMP Traffic303
Chapter 16 Configuring Port Security311
- Understanding How Port Security Works311
- Port Security Configuration Guidelines313
- Configuring Port Security on the Switch313
- Monitoring Port Security320
Chapter 17 Configuring Unicast Flood Blocking323
- Understanding How Unicast Flood Blocking Works323
- Configuration Guidelines for Unicast Flood Blocking324
- Configuring Unicast Flood Blocking on the Switch324
Chapter 18 Configuring the IP Permit List327
- Understanding How the IP Permit List Works327
- IP Permit List Default Configuration328
- Configuring the IP Permit List on the Switch328
Chapter 19 Configuring Protocol Filtering333
- Understanding How Protocol Filtering Works333
- Default Protocol Filtering Configuration334
- Configuring Protocol Filtering on the Switch334
  - Configuring Protocol Filtering334
  - Disabling Protocol Filtering335
CHAPTER 20 Checking Status and Connectivity 20-1337
- Checking Module Status337
- C H a P T E R 20 Checking Status and Connectivity338
- Checking Port Status338
- Displaying the Port MAC Address340
- Displaying Port Capabilities341
- Using Telnet342
- Changing the Login Timer342
- Using Secure Shell Encryption for Telnet Sessions343
- Monitoring User Sessions344
- Using Ping345
  - Understanding How Ping Works345
  - Executing Ping346
- Using Layer 2 Traceroute347
  - Layer 2 Traceroute Usage Guidelines347
  - Identifying a Layer 2 Path347
- Using IP Traceroute348
  - Understanding How IP Traceroute Works348
  - Executing IP Traceroute349
Chapter 21 Configuring CDP351
- Understanding How CDP Works351
- Default CDP Configuration351
- Configuring CDP on the Switch352
Chapter 22 Using Switch Topn Reports357
- Understanding How Switch Topn Reports Works357
- Running and Viewing Switch Topn Reports359
Chapter 23 Configuring UDLD363
- Understanding How UDLD Works363
- UDLD Software and Hardware Requirements364
- Default UDLD Configuration364
- Configuring UDLD on the Switch365
- Snmp Terminology371
Chapter 24 Configuring SNMP372
- SNMP Terminology372
- Understanding How SNMP Works373
- Understanding How Snmpv1 and Snmpv2C Work375
  - Snmpv1 and Snmpv2C Default Configuration376
- Understanding Snmpv3376
  - Benefits of Snmpv3376
  - SNMP Entity376
- Configuring SNMP from an NMS379
- Configuring Snmpv1 and Snmpv2C from the CLI380
  - Snmpv1 and Snmpv2C Enhancements in Software Release380
  - Setting Multiple Snmp Community Strings381
- Configuring Snmpv3 from the CLI384
- Using Ciscoworks2000387
- Using Ciscoworks2000388
Chapter 25 Configuring RMON389
- Understanding How RMON Works389
- Enabling RMON390
- Viewing RMON Data390
- Supported RMON and RMON2 MIB Objects391
Chapter 26 Configuring SPAN and RSPAN393
- Understanding How SPAN and RSPAN Work393
- Vspan395
Chapter 27 Administering the Switch411
- Setting the System Name and System Prompt411
  - Configuring the System Name and Prompt412
- Setting the System Contact and Location413
- Setting the System Clock414
- Creating a Login Banner414
  - Configuring a Login Banner414
  - Clearing the Login Banner415
Enabling or Disabling the "Cisco Systems Console" Telnet Login Banner415
- Defining and Using Command Aliases416
- Defining and Using IP Aliases417
- Configuring Permanent and Static ARP Entries418
- Configuring Static Routes419
- Scheduling a System Reset420
  - Scheduling a Reset at a Specific Time420
  - Scheduling a Reset Within a Specified Amount of Time421
- Generating System Status Reports for Tech Support422
Chapter 28 Power Management423
- Understanding How Power Management Works on the Catalyst 4500 Series Switches423
- Understanding How Power Management Works on the Catalyst 4006 Switch428
- Power Consumption for Modules431
- Migrating a Supervisor Engine II from a Catalyst 4006 Switch to a Catalyst 4500 Series Switch432
- Understanding How Poe Works433
- Configuring Power Management436
- Configuring Poe440
Chapter 29 Configuring Voip443
- Hardware and Software Requirements443
- Overview of IP Phones444
- Configuring Voip on a Switch445
- Configuring Voip on a Switch446
Chapter 30 Configuring Switch Access Using AAA447
- Understanding How Authentication Works447
- Configuring Authentication454
- Authentication Example485
- Understanding How Authorization Works486
- Configuring Authorization488
- Authorization Example492
- Understanding How Accounting Works493
- Configuring Accounting495
- Accounting Example499
Chapter 31 Configuring 802.1X Authentication501
- Understanding How 802.1X Authentication Works501
- Authentication Default Configuration509
- Authentication Configuration Guidelines509
- Configuring 802.1X Authentication on the Switch510
Chapter 32 Modifying the Switch Boot Configuration521
- Understanding How the Switch Boot Configuration Works521
- Default Switch Boot Configuration524
- Setting the Configuration Register524
- Setting the BOOT Environment Variable526
  - Clearing the BOOT Environment Variable Settings527
- Setting and Clearing the CONFIG_FILE Environment Variable527
  - Setting the CONFIG_FILE Environment Variable527
  - Clearing CONFIG_FILE Environment Variable Entries528
- Displaying the Switch Boot Configuration528
Chapter 33 Working with System Software Images529
- Software Image Naming Conventions529
- Downloading System Software Images to the Switch Using TFTP529
- Uploading System Software Images to a TFTP Server532
  - Preparing to Upload an Image to a TFTP Server533
  - Uploading Software Images to a TFTP Server533
- Downloading System Software Images to the Switch Using Rcp533
- Uploading System Software Images to an Rcp Server536
  - Preparing to Upload an Image to an Rcp Server537
  - Uploading Software Images to an Rcp Server537
- Upgrading the ROM Monitor537
Chapter 34 Working with the Flash File System543
- Working with the Flash File System on the Switch543
Chapter 35 Working with Configuration Files551
- Creating and Using Configuration Files Guidelines551
- Creating a Configuration File552
- Configuring the Switch Using a File in Flash Memory552
- Copying Configuration Files Using TFTP553
  - Downloading Configuration Files from a TFTP Server553
  - Uploading Configuration Files to a TFTP Server554
- Copying Configuration Files Using Rcp555
  - Downloading Configuration Files from an Rcp Server556
  - Uploading Configuration Files to an Rcp Server557
- Clearing the Configuration558
Chapter 36 Configuring Switch Acceleration559
- Understanding How Switch Acceleration Works559
- Configuring Switch Acceleration on the Switch561
  - Enabling Switch Acceleration561
  - Displaying Switch-Acceleration Information561
- Backplane Channel Module562
Chapter 37 Configuring System Message Logging563
- Understanding How System Message Logging Works563
- System Log Message Format565
- Default System Message Logging Configuration565
- System Log Message Format566
- Configuring System Message Logging on the Switch566
Chapter 38 Configuring DNS573
- Understanding How DNS Works573
- Default DNS Configuration574
- Configuring DNS on the Switch574
Chapter 39 Configuring NTP577
- Understanding How NTP Works577
- Default NTP Configuration578
- Configuring NTP on the Switch578
- Clearing the Time Zone583
- Clearing NTP Servers583
- Disabling NTP584
Appendix585
Appendix A Acronym586
I N D E X595

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