Network: Cisco first (basic) configuration, reset

router Bootup process

To use a UTP cable for consoling into a Cisco router from a PC serial port, it must be terminated as a rollover or console cable.

When you turn the router on, it runs through the following boot process.

The Power-On Self Test (POST) checks the router’s hardware. When the POST completes successfully, the System OK LED indicator comes on.
The router checks the configuration register to identify where to load the IOS image from. A setting of 0x2102 means that the router will use information in the startup-config file to locate the IOS image. If the startup-config file is missing or does not specify a location, it will check the following locations for the IOS image:

1. Flash (the default location)
2. TFTP server
3. ROM (used if no other source is found)

The router loads the configuration file into RAM (which configures the router). The router can load a configuration file from:

  1. NVRAM (startup-configuration file)
  2. TFTP server
    If a configuration file is not found, the router starts in setup mode.
enable password cisco
line vty 0 12
  transport input all
  password cisco

Switch steps 0-2, router steps 1-2.

0. delete flash:vlan.dat – Remove the LVAN database information file from FLASH on Switch.

Delete filename [vlan.dat]?
Delete flash:/vlan.dat? [confirm]
%Error deleting flash:/vlan.dat (No such file or directory) – в случае если файл не создан, VLAN нет
VLAN’ы на коммутаторе по умолчанию (VTP Server) хранятся в файле vlan.dat во flash (или разделе NVRAM). Причем чтение файла осуществляется только единожды – при загрузке коммутатора. Далее все VLAN’ы выгружаются в оперативную память и остаются там (это называется memory-resident). По этой причине после удаления файла vlan.dat через delete flash:vlan.dat не приводит к исчезанию vlan’ов в show vlan. При изменении VLAN коммутатор изменяет содержимое в оперативной памяти  и параллельно делает запись в файл vlan.dat. Аналогично, думаю, справдливо и для конфига коммутатора в NVRAM.

memory-resident program A program that once loaded into memory stays there and can be accessed or reactivated whenever necessary without having to load another copy from disk.
  1. erase startup-config – Remove the device startup configuration file from NVRAM.
Erasing the nvram filesystem will remove all configuration files! Continue? [confirm]


Erase of nvram: complete

2. reload – Restart the software for clean RAM from VLAN database and running-config.

%SYS-5-RELOAD: Reload requested by console. Reload Reason: Reload Command.



Тут подробный man.

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