ISR G1 2800/3800 Series Internal flash memory

mhiyoshi · ‎09-16-2011

Hello

I have a question about Cisco ISR G1 2800, 3800 internal flash memory

the related URL is below

[Overview of Cisco 2800 Series Routers]
http://www.cisco.com/en/US/docs/routers/access/2800/hardware/installation/guide/01_hw.html#wp1037629

[Overview of Cisco 3800 Series Routers]
http://www.cisco.com/en/US/docs/routers/access/3800/hardware/installation/guide/38over.html#wp1008587

What purpose is the internal 2MB 4MB flash memory?

Is this just for booting ROMMON image?

I am just thinking if this memory can use for booting IOS image without compact flash memory

just as regacy Cisco2600, 2500 will do normally.

It must be very usefull

Thank you and regards,

Latchum Naidu · ‎09-16-2011

Hi,

Usually flash memory is commonly used to store Cisco IOS software and configuration files, also some high-end systems, Flash memory is also used to hold bootstrap software.

ROM—ROM is generally the memory on a chip or multiple chips. It is available on a router's processor board. It is read-only, which means that data cannot be written to it. The initial software that runs on a Cisco router is called the bootstrap software and is usually stored in ROM. The bootstrap software is invoked when the router boots up.
Flash—Flash memory is located on a processor board SIMM but can be expanded using PCMCIA (removable) cards. Flash memory is most commonly used to store one or more Cisco IOS software images. Configuration files or system information can also be copied to Flash. On some high-end systems, Flash memory is also used to hold bootstrap software.
RAM—RAM is very fast memory that loses its information when the system is restarted. It is used in PCs to store running applications and data. On a router, RAM is used to hold IOS system tables and buffers. RAM memory is basically used for all system operational storage requirements.
NVRAM—On the router, NVRAM is used to store the startup configuration. This is the configuration file that IOS reads when the router boots up. It is extremely fast memory and is persistent across reboots.

Please rate the helpful posts.

Regards,

Naidu.

Joseph W. Doherty · ‎09-16-2011

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

[Overview of Cisco 2800 Series Routers]

http://www.cisco.com/en/US/docs/routers/access/2800/hardware/installation/guide/01_hw.html#wp1037629

[Overview of Cisco 3800 Series Routers]
http://www.cisco.com/en/US/docs/routers/access/3800/hardware/installation/guide/38over.html#wp1008587

What purpose is the internal 2MB 4MB flash memory?

Is this just for booting ROMMON image?

For your 1st question, from your first reference:

Boot/NVRAM—Internal flash memory. Stores the bootstrap program (ROM monitor), the configuration register, and the startup configuration.

So, the answer to your 2nd question is "no" to "just for".

Remember config files can get large, for example if you have lots of ACLs. Many routers even offer an option to compress the config file when its stored to reduce its physical storage needs.

Also, on later routers, the bootrom can be upgraded, i.e. it's not stored in real ROM anymore (which on older routers used to required swapping chips to upgrade).

mhiyoshi · ‎09-22-2011

Thank you very much for a lot of precious information!!

I have been reading these information, then I have more question about this.

I think does ISR G1 internal flash memory combine like Boot ROM and NVRAM together?

If so where is NVRAM in ISR G1?

Can I store IOS image into internal flash memory without compact flash?

Masanobu Hiyoshi

Joseph W. Doherty · ‎09-22-2011

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

"I think does ISR G1 internal flash memory combine like Boot ROM and NVRAM together?"

I suspect they are physically different, although they might use the same technology.

"If so where is NVRAM in ISR G1?"

Probably an EEPROM or similar chip on the motherboard.

"Can I store IOS image into internal flash memory without compact flash?"

I'm not sure. There would be insufficient space on the NVRAM for an IOS image. I don't believe these devices have internal flash for IOS images other than using a CF card. However, on at least some of the 2800s, you can store an IOS image on USB, and boot from it, if the ROMMOM is current.