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How to Reset a Cisco Router or Switch to Factory Default

What if we forget the login credentials of our Cisco routers or switches and we are not able to log in to make changes in configuration? To reset the Cisco router or switch is one of the quickest ways to resolve the issue. It will make a new and blank startup configuration file, and it will show you the setup wizard for a quick configuration of the router.

But what if we want to retain the existing configuration on the router? Another solution is to perform a password recovery on the router. We will discuss how to restore our Cisco routers and switches to the factory defaults and also how to implement password recovery on them.

Factory Reset on Cisco Router or Switch IOS

The following procedure is the steps when we are going to factory reset a Cisco router.

1. In the global configuration mode, create a hostname first on the router as we will use it for verification if the router is already reset into the factory settings.

Router(config)#hostname Router 1

2. Verify the configuration by using one of the following commands.

Router 1#sh running-config Building configuration. Current configuration: 526 bytes ! version 15.1 no service timestamps log datetime msec no service timestamps debug datetime msec no service password-encryption ! hostname Router 1 ! !

3. Save the configuration using the ‘copy running-config startup-config’ command.

Router 1#copy running-config startup-config Router 1#write

4. Resetting the Cisco router to factory default involves erasing the NVRAM.

Router 1#write erase Erasing the nvram filesystem will remove all configuration files! Continue? [confirm]y[OK] Erase of nvram: complete %SYS-7-NV_BLOCK_INIT: Initialized the geometry of nvram

5. Reload the Cisco router to complete resetting to the factory defaults, and the startup wizard or initial system configuration dialog will appear.

6. Verify if the Cisco router is reset to factory default by checking if “hostname Router 1” is disappeared and changed to default.

Router#sh running-config Building configuration. Current configuration: 584 bytes ! version 15.1 no service timestamps log datetime msec no service timestamps debug datetime msec no service password-encryption ! hostname Router ! !

Password Recovery on Cisco IOS

Before we proceed with password recovery, we will take a look first at the configuration register. We can use the ‘show version’ command to check the configuration register setting on our device. Configuration Register is a special 16 bits value that can be configured in Cisco routers. It is mainly used to determine how the router boots, to determine boot options, and to set console speed. The following are the most commonly used configuration register settings:

• config-register 0x2102 – boot normally (default configuration register setting)
• config-register 0x2120 – boot into ROM Monitor (ROMMON)
• config-register 0x2142 – ignore contents of NVRAM (startup-configuration)

The following procedure is the steps when we are going to recover the forgotten enable password or enable secret command configured in our Cisco router or switch.

2. Press the break sequence (ctrl-Break) while the router is initializing to break into ROMMON prompt.

3. Follow this command, confreg 0x2142, to ignore the startup-configuration and reset or reload the router.

rommon 1 > confreg 0x2142 rommon 2 > reset

4. After reboot, it will not ask you the secret password and will proceed to the setup wizard or initial system configuration dialog, as it booted up with a blank configuration.

5. The startup-configuration is still there with the full configuration, including the unknown enable secret, but the router does not use it when it boots. Enter a new enable secret in global configuration mode to overwrite the old one. This will go into the running-config.

Router(config)#enable secret cisco12345

6. In the global configuration mode, configure the configuration register back to default by entering the ‘config-register 0x2102’ router command, so the router will boot normally on the next restart.

Router(config)#config-register 0x2102

7. Save the configuration. This will merge the new enable password into the existing startup-configuration.

Router#copy running-config startup-config

8. Reboot the router using the ‘reload’ command and see that the secret password is changed to the one we configured earlier.

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• IOS Basic Commands
• Configure an IP Address on a Switch
• Configure Descriptions
• Interface Range Command
• Power on a Cisco Device
• Half Duplex and Full Duplex
• Configure Speed and Duplex
• Link Layer Discovery Protocol (LLDP)
• Cisco Discovery Protocol (CDP) overview
• show Command
• show interfaces status Command
• Interface Status Codes
• show version Command

• OSPF Overview
• Differences Between OSPF and EIGRP
• Cisco Bandwidth Command vs Clock Rate and Speed Commands
• OSPF Cost — OSPF Routing Protocol Metric Explained
• OSPF Configuration
• Designated & Backup Designated Router
• OSPF Passive Interface — Configuration and Why it is Used
• OSPF Default-Information Originate and the Default Route
• OSPF Load Balancing — Explanation and Configuration
• OSPF Summarization
• Troubleshooting OSPF and OSPF Configuration Verification
• OSPF Network Types — Point-to-Point and Broadcast
• OSPF Summary

• Cisco Three-Layer Hierarchical Model
• Collapsed Core and Three-Tier Network Architectures
• What is Spine and Leaf Network Architecture?
• What is a VLAN?
• Frame Tagging
• Configuring VLANs
• Access and Trunk Ports
• Inter-Switch Link (ISL)
• IEEE 802.1Q
• Configuring Access & Trunk Ports
• Configuring Voice VLANs
• Configuring Allowed VLANs
• Cisco Dynamic Trunking Protocol (DTP) Explained
• What is VTP?
• VTP Modes
• VTP Configuration

• What is STP?
• Network Bridge Explained
• How STP Works
• Electing the Root Switch in STP
• Spanning Tree Priority: Root Primary and Root Secondary
• Selecting STP Root Port
• Selecting STP Designated Port (DP)
• Spanning Tree Modes: MSTP, PVST+, and RPVST+
• What is RSTP?
• How RSTP Works
• Configuring RSTP
• Cisco HSRP and Spanning Tree Alignment Configuration
• Spanning Tree Portfast, BPDU Guard, Root Guard Configuration

• What is IPv6?
• IPv6 Address Format
• IPv6 Interface Identifier
• Differences Between IPv4 and IPv6
• Types of IPv6 Addresses
• How to Configure IPv6
• IPv6 SLAAC — Stateless Address Autoconfiguration
• IPv6 Routing — Static Routes Explained and Configured
• IPv6 Default Static Route and Summary Route
• IPv6 Routing Protocols
• Neighbor Discovery Protocol — NDP Overview

• Telnet & SSH
• Setting Up Telnet
• Setting Up SSH
• Cisco Console Port Security
• exec-timeout Command
• Encrypt Local Usernames and Passwords
• Cisco Privilege Levels — Explanation and Configuration
• What is AAA? Authentication, Authorization, & Accounting
• Configuring AAA on Cisco Devices – RADIUS and TACACS+
• Configuring a Cisco Banner: MOTD, Login, & Exec Banners
• Configure Timezone and Daylight Saving Time (DST)
• NTP (Network Time Protocol)
• Configure NTP on a Cisco Router

• What is Network Automation and Why We Need It?
• Network Programmability — Git, GitHub, CI/CD, and Python
• Data Serialization Formats — JSON, YAML, and XML
• SOAP vs REST: Comparing the Web API Services
• Model-Driven Programmability: NETCONF and RESTCONF
• Configuration Management Tools — Ansible, Chef, & Puppet
• Cisco SDN — Software Defined Networking Explained
• Cisco DNA — Digital Network Architecture Overview
• Cisco IBN — Intent-Based Networking Explained
• Cisco SD-Access (Software-Defined Access) Overview
• Cisco SD-WAN (Software-Defined WAN) Overview & Architecture

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Артём Санников

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Команды для конфигурирования устройств Cisco

Вход/Выход/Перезагрузка

enable — вход в привилегированный режим EXEC

exit — команда для возвращения назад по дереву конфигурирования

Безопасность

enable password — безопасный доступ к привилегированному режиму

enable secret — зашифрованный пароль для доступа к привилегированному режиму

service password-encryption — шифрование паролей enable и console

line console 0 — безопасный доступ к консоли

Справочная информация

router ? — список поддерживаемых протоколов маршрутизатора

Тайм-ауты

exec-timeout — увеличение времени таймаута

SHOW

show — фильтрация выходных данных

show flash — проверка содержимого флеш-памяти

show running-config — Вывод текущей конфигурации коммутатора/маршрутизатора

show ip interface brief — сведения об IP-адресе, портах и интерфейсах устройства

show ip router — вывод таблицы маршрутизации

show vlan — вывод сведений о существующих VLAN.

IPv4

ip address — настройка параметров IPv4 на интерфейсе маршрутизатора

ip route — настройка статического маршрута IPv4

ip default-gateway — шлюз по умолчанию для коммутатора

IPv6

show ipv6 route static — проверка статических маршрутов IPv6

ipv6 route — настройка статического маршрута IPv6

ipv6 address — настройка параметров IPv6 на интерфейсе маршрутизатора

ipv6 unicast-routing — включение пересылки IPv6 пакетов на маршрутизаторе

LOOPBACK

interface loopback — настройка интерфейса loopback на маршрутизаторе

VLAN

vlan — объявление (создание) нового VLAN

name — присвоение имени для VLAN

interface vlan — настройка IP-адреса для интерфейса VLAN коммутатора

Работа с интерфейсами

int range — выбор интерфейсов в указанном диапазоне

Файлы конфигурации

erase startup-config — сброс настроек конфигурации startup-config

copy startup-config flash — сохранение файла загрузочной конфигурации во флеш-память

copy running-config startup-config — сохранение файлов конфигурации в NVRAM

Протокол DHCP

Настройка DHCP пула — Полная настройка DHCP пула на сетевом устройстве

ip dhcp poo l — Создание нового пула DHCP

network — Диапазон сети для пула DHCP

defaul-router — Шлюз по умолчанию для пула DHCP

dns-server — DNS-адрес сервера для пула DHCP

lease — Срок аренды IP-адреса для пула DHCP

domain-name — Адрес домена для пула DHCP

ip dhcp excluded-address — Исключение IP-адреса из пула DHCP

Port-Security

switchport port-security — Активация функции port-security

switchport port-security maximum — Количество MAC-адресов на порт устройства

switchport port-security mac-address sticky — Запись MAC-адреса в рабочую конфигурацию (липкие MAC-адреса)

switchport port-security violation — Запрет на передачу данных для MAC-адресов

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