You can generally tell how much flash memory you need on the Cisco router by looking at the size of the IOS file you want to load. If the file size is 12 or 14MB, then you round up to the next 8MB increment of flash, which would be 16MB (ex. 8MB, 16MB, 24MB, 36MB). This is a loose rule, but pretty safe to follow most of the time.
In addition, just because you have enough flash memory to burn the IOS file into flash doesn't mean it will be able to run successfully on your Cisco router. Why not? Let's say your Cisco router has 4MB of DRAM and 16MB of flash. Some of the newer IOS files will require additional DRAM. Check the IOS file requirements for flash, but also make sure you meet the DRAM memory requirements.
Now you have enough DRAM and flash memory in the Cisco router to load the IOS, but it still won't load. The error message says there isn't enough available flash. Why, when you have two 8MB flash sticks in the router, equaling 16MB? Most likely, the flash is partitioned; you don't have enough contiguous space to load the IOS.
How can you tell? There are one of two ways:
First, when your router boots, you may see something during the POST like below. Note the two partitions in bold:
cisco 2500 (68030) processor (revision L) with 14332K/2048K bytes of memory.
Processor board serial number 02094596
X.25 software, Version 2.0, NET2, BFE and GOSIP compliant.
Authorized for Enterprise software set. (0x0)
1 Ethernet/IEEE 802.3 interface.
2 Serial network interfaces.
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash partition 1 (Read ONLY)
8192K bytes of processor board System flash partition 2 (Read/Write)
See how the flash is broken into two 8MB partitions instead of one 16MB contagious partition? That is the issue!
The second way is to run the 'show flash' command in privileged mode. You will definitely want to be familiar with the show commands for your CCNA exam. You can see two partitions in the example below:
8192K bytes of processor board System flash (Read/Write)
Can you just run the 'no partition flash' command and make it one big partition? No - it won't be that easy.
If you see an IOS image in partition 2, you need to delete it before you can proceed to the 'no partition flash' command; otherwise it will error out. You can erase the IOS file in partition 2 by following the example below:
Router# erase flash
Partition Size Used Free Bank-Size State Copy Mode
16384K bytes of processor board System flash (Read/Write)
At this point, you can start your IOS upgrade with the 'copy tftp flash' command by following the article from our site. You are now on your way to understanding Cisco routers and obtaining your Cisco CCNA certification!Avoid expensive repairs and recovery costs. At Future Trends.com our network monitoring and maintenance will save you money by preventing expensive network disasters from ever happening in the first place. Visit us online for any los angeles it consulting or computer consulting.