What is NVRAM used to store in a Cisco switch?

NVRAM, or Non-Volatile Random Access Memory, is specifically used in Cisco switches to store the startup configuration file. This configuration file contains the settings and parameters that are applied to the switch when it is powered on or restarted. The startup configuration is crucial for the switch to know how to operate and what settings to apply in order to perform its functions properly once it's up and running.

When a switch is powered up, it first loads its IOS from flash memory, and then it accesses NVRAM to retrieve the startup configuration. Because NVRAM retains its contents even when power is lost, it ensures that the configuration persists across reboots, allowing the switch to maintain its configured state without the need for manual reconfiguration after every restart.

The running configuration, stored in RAM, reflects the current operational settings of the switch, but does not survive a reboot. The IOS image is stored in flash memory, and the VLAN database is typically stored in the VLAN.dat file, which also resides in flash memory rather than NVRAM. Thus, NVRAM’s exclusive role in maintaining the startup configuration makes it an essential component of Cisco switch architecture.