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Q
What is Cisco flash memory?
A
Cisco flash memory is non-volatile storage on routers and switches that holds the OS image, configuration files, and logs. It retains data without power and enables device boot and software upgrades.
Q
What is the difference between Cisco flash and NVRAM?
A
Cisco flash stores IOS images, files, and logs persistently, while NVRAM holds the device’s running-configuration only. Flash capacity is larger for software storage; NVRAM is optimized for config retention.
Q
How do I check flash memory usage on a Cisco device?
A
Run the CLI command show flash: or show file systems to display total, used, and free flash space. Look for “flash:” or “bootflash:” entries to view detailed usage statistics.
Q
How can I free up space on Cisco flash memory?
A
Delete unneeded files with delete flash:<filename> or archive old IOS images to a TFTP/FTP server using the copy command. Then verify free space with show flash:.
Q
Can I upgrade Cisco flash memory and how?
A
Yes. Power off your device, install a higher-capacity CompactFlash, SD/microSD card, or bootflash module supported by your model, then power on, format, and copy the IOS image to flash via copy tftp: flash:.
Q
What types of flash modules are supported by Cisco routers?
A
Cisco routers support CompactFlash, industry-standard SD/microSD cards, USB flash drives, and proprietary bootflash modules. Check your hardware installation guide for capacity limits and compatibility.
Q
How do I replace a flash memory module in a Cisco switch?
A
Power off the switch, remove the slot cover, extract the existing flash card, and insert the new module until it clicks. Power on, verify with show flash:, and format if required.
Q
What is Cisco bootflash?
A
Cisco bootflash is a dedicated flash partition that stores the bootloader and IOS image separately from primary flash. It ensures reliable system startup by isolating critical boot files.
Q
How much flash memory does the Cisco Catalyst 9000 series support?
A
Catalyst 9000 series switches support up to 16 GB of internal bootflash and up to 64 GB of external USB flash storage. Capacity varies by model—refer to the datasheet for exact specifications.
Q
What is the difference between DRAM and flash on Cisco devices?
A
DRAM is volatile memory used for running IOS processes, routing tables, and packet buffering, losing content on reload. Flash is non-volatile storage that retains images and files when powered off.
Q
How reliable is Cisco flash memory?
A
Cisco flash uses industrial-grade NAND/NOR technology with built-in error correction and wear-leveling for high endurance. It meets enterprise-class standards for continuous read/write cycles.
Q
Can I use USB drives as flash on Cisco devices?
A
Most modern Cisco routers and switches support USB flash drives for IOS images, configurations, and file storage. After insertion, use copy usb0: flash: to transfer data.
Q
What file systems are supported on Cisco flash memory?
A
Cisco flash supports FAT16, FAT32, ext2/ext3, and Cisco’s proprietary file system. Use show file systems to list supported volumes and format partitions as needed.
Q
How do I recover a corrupted flash memory image?
A
Boot into ROMmon mode, configure IP and TFTP settings, then use tftpdnld to download a fresh IOS image to flash. Reset boot variables and reload to finalize recovery.
Q
What is the maximum capacity of flash memory on Cisco ISR 4000 series?
A
ISR 4000 series routers support up to 8 GB of internal flash and up to 32 GB via external USB flash. Capacity may vary by specific model and software requirements.
Q
How do I back up Cisco flash memory configurations?
A
Use the CLI command copy flash:<filename> tftp: or copy flash:<filename> scp: to transfer config files or IOS images to a remote server. Always verify checksum after transfer for data integrity.
