CCNA Cisco Certified Network Associate Study Guide - FTP Server

Erasing the Switch Configuration
Cisco 1900 IOS Configuration Commands 587
The switch configuration is stored in NVRAM, just as any router. You cannot
view the startup-config, or contents of NVRAM. You can only view the
running-config. When you make a change to the switches’ running-config,
the switches automatically copy the configuration on the switch to NVRAM.
This is a big difference from a router where you have to type copy runningconfig
startup-config. That option is not available on the 1900 switch.
You can delete the configuration in NVRAM on the 1900 switch if you
want to start over on the switches’ configuration. To delete the contents of
NVRAM on a 1900 switch, use the delete nvram command.
Notice in the switch output below that there are two options: nvram and
vtp. I want to delete the contents of NVRAM to the factory default settings.
Todd1900EN#delete ?
nvram NVRAM configuration
vtp Reset VTP configuration to defaults
Todd1900EN#delete nvram
This command resets the switch with factory defaults. All
system parameters will revert to their default factory
settings. All static and dynamic addresses will be
removed.
Reset system with factory defaults, [Y]es or [N]o? Yes
Notice the message received from the switch when the command delete
nvram is used. Once you say yes, the configuration is gone.
Managing the MAC Address Table
Do you remember how bridges and switches filter a network? They use
MAC (hardware) addresses burned into a host’s network interface card
(NIC) to make forwarding decisions. The switches create a MAC table that
includes dynamic, permanent, and static addresses. This filter table is created
by hosts sending a frame and by the switch learning the source MAC address
and from which segment and port it was received.
The switch keeps adding new MAC addresses that are sent on the network
into the MAC filter table. As hosts are added or removed, the switch
dynamically updates the MAC filter table. If a device is removed, or if it is
not connected to the switch for a period of time, the switch will age out the
entry.