Question 1

What is the default DRAM and flash memory configuration on a Cisco 3900 Series router?

Accepted Answer

Cisco 3900 Series routers ship with 512 MB or 1 GB of DRAM and 128 MB or 256 MB of flash memory, depending on the exact model and IOS feature set.

Question 2

What is the maximum DRAM supported by the Cisco 3900 Series router?

Accepted Answer

Cisco 3900 routers support up to 4 GB of DRAM when you install compatible DDR2 SODIMM modules in both memory slots.

Question 3

How can I verify the DRAM and flash memory on my 3900 router?

Accepted Answer

Use the EXEC command show version or show platform hardware capacity to display installed DRAM and flash memory on a Cisco 3900 Series router.

Question 4

How do I upgrade DRAM on a Cisco 3900 Series router?

Accepted Answer

Power down the router, open the top cover, install matching DDR2 SODIMM modules in both memory slots, then reassemble and power up to activate the new DRAM.

Question 5

How do I upgrade flash memory on a Cisco 3900 Series router?

Accepted Answer

Power off the router, insert the supported CompactFlash card into the front slot, power on, and verify with show flash: to confirm the new capacity.

Question 6

What are the recommended memory modules for Cisco 3900 Series routers?

Accepted Answer

Use Cisco-approved DDR2 PC2-4200 SODIMMs for DRAM and Cisco-branded 256 MB, 512 MB or 1 GB CompactFlash cards for flash to ensure compatibility and stability.

Question 7

Why is DRAM important for 3900 router performance?

Accepted Answer

DRAM handles routing tables, process queues, and feature operations; adequate DRAM prevents slow routing updates and supports advanced IOS features.

Question 8

Why is flash memory critical for Cisco 3900 routers?

Accepted Answer

Flash stores the IOS image, configuration files, and logs; sufficient flash capacity ensures room for multiple IOS versions and recovery images.

Question 9

How does insufficient DRAM affect router performance?

Accepted Answer

Low DRAM can cause IOS feature failures, routing protocol flaps, and system reloads due to memory exhaustion under heavy traffic or feature loads.

Question 10

How do I troubleshoot memory-related errors on a 3900 Series router?

Accepted Answer

Check logs with show logging, monitor memory pools via show platform hardware capacity, and run diagnostic tests using diagnostic start module all.

Question 11

Can I mix different DRAM module sizes on Cisco 3900 routers?

Accepted Answer

No, both SODIMM slots must contain matched DDR2 modules of the same capacity and speed for proper operation.

Question 12

How do I clear or reset flash memory on a 3900 router?

Accepted Answer

Use the erase flash: command in privileged EXEC mode, then reload the router to remove all files and reset flash to factory state.

Question 13

What memory configuration is required for Cisco IOS feature sets on a 3900 router?

Accepted Answer

Advanced security or unified communications feature sets typically require at least 2 GB DRAM and 512 MB flash for optimal performance and future upgrades.

Question 14

How does flash memory impact firmware upgrades on a 3900 Series router?

Accepted Answer

Ample flash ensures you can store both the running and new IOS images simultaneously, enabling rollback if the upgrade fails.

Question 15

What best practices should I follow for managing memory on Cisco 3900 routers?

Accepted Answer

Regularly monitor memory usage, maintain IOS images and backups in flash, use approved modules, and schedule upgrades before reaching capacity thresholds.

Question 16

How do I back up and restore flash contents on a Cisco 3900 Series router?

Accepted Answer

Use the copy flash: tftp: command to back up and copy tftp: flash: to restore, ensuring you specify correct file paths and IP addresses.

Router Memory & Flash Components

MEM-3900-1GU4GB-UPG 4GB FROM 1GB DRAM 2GB+2GB FOR 3925/3945 ISR

MEM-3900-1GU2GB-1GB to 2GB DRAM Upgrade (1GB+1 GB) for Cisco 3925/3945 ISR

MEM-3900-1GB=-1GB DRAM (1 DIMM) for Cisco 39 25/3945 ISR, Spare

MEM-3900-2GB=-2GB DRAM (1 DIMM) for Cisco 39 25/3945 ISR, Spare

MEM-3900-512MB=-512MB DRAM 1 DIMM FOR CISCO 39 25/3945 ISR SPARE

Filters

Questions & Answers

What is the default DRAM and flash memory configuration on a Cisco 3900 Series router?

What is the maximum DRAM supported by the Cisco 3900 Series router?

How can I verify the DRAM and flash memory on my 3900 router?

How do I upgrade DRAM on a Cisco 3900 Series router?