Is It True about NVRAM

Is It True ?
NVRAM is a partition of Flash memory in all Cisco devices. They are not seperate chips.
Although this picture may show that, it's only for discussion to make sure that you know that NVRAM and FLASH are used for completely different reasons.
Todd Lammle

 

The
reason I ask is because I remember seeing a topic where someone had
purchased a router from ebay. They did a basic power on test when the
receive it to make sure it booted properly then set it aside for a
while.


Later, when they were ready to put
it
into service in their Lab Rack, they found it would not allow them to
save the config to NVRAM. Attempts at copy run start or wr received a
""NVRAM Verification Failed" error.


According
the the link below, there were actually 2 2650XM routers. According to
this thread, it appears that someone harvested the nvram chips at some
point prior to the vendor shipping the routers to this person. Once they
addressesd this with the vendor, replacement chips we sent and
installed and problems solved.


http://www.techexams.net/.../50540-fried-nvram.html

I
have not looked into this further, but I suspect that all the
2600/2600XM series are the same. I also know that I can remove the CF
(Flash Card) from my 2811 and 2821 and still be able to write config
changes to nvram without throwing an error. When I reboot, with the
flash card re-installed, it reloads with the config saved just prior to
reboot (confirmed while writing this post).


As
I think back about the various flash memory upgrades I have done with
routers I own or purchased and sold, 2600 series, 3600 series, and
1760s, I never lost an existing config when changing flash memory
modules. If, as you say, "NVRAM is a partition of Flash memory in all
Cisco devices. They are not seperate chips." then any configurations
stored on that partition on the flash module would move with the module
(much the same as removing a HD containing partitions from a PC and
replacing it with a HD with completely different partitions) and not
remain on the router!


From this, I think you may understand my confusion and thus my question.

Comments

  • Hi,

    Flash is a separate memory in the Cisco ISRs & Non-ISRs. I'm not sure about the purticular platform that you mentiond above but Non-ISRs also have separate memory as a Flash & NVRAM. Please check with other platforms as well, you will get more information on it.

    Previously, I have worked with a Cisco3620 Series router which was connected to the VSAT. When I found that the OS was crashed, we tried to recover it re-installing IOS but unable to solve the issue without changing the flash. Once changed, the old configuration worked well.

    So in my opinion, it could be due to platform specification. Additionally, try issuing " erase flash:" command & check what happens. 

    Hope this helps!

  • Lets see What other CCIE says .... But its the view of Tod lamle ....

  • peetypeety ✭✭✭

    Lets see What other CCIE says .... But its the view of Tod lamle ....

    Say what?  Someone who's a CCIE hasn't ever been tested on the nature of the underlying hardware.  Why are you so fired up about this?

    Just log into some devices and do a show version.

    On a 3550 switch:

    r4s2#sh ver | i flash
    System image file is "flash:/c3550-ipservicesk9-mz.122-44.SE6.bin"
    384K bytes of flash-simulated NVRAM.
    r4s2#

    On an 1841 router:

    Practice#sh ver | i NVRAM
    191K bytes of NVRAM.
    Practice#

    It's simulated on some devices, there you go.  Now move onto the next question.

  • First, I would expect this question to arise in a CCNA forum - but would also not expect most CCIEs to know details of hardware architecture on most platforms.

     

    NVRAM, what is that?

    Back in the days - happy 80ies and 90ies it used to be a SRAM, with a battery included. Batteries have limited lifetime, so it is not a good long time solution.

    This evolved into erasable ROM chips, EEPROM and flash.

    So I would expect to see the configuration stored on various types of memory on different platforms.

     

    Even on different models of 2600 this will be different:

    Cisco documents EPROM, which is a kind of memory erasable by UV light. Dont think this documentation can be correct:

    -NVRAM is used for writable permanent storage of the startup configuration. It is an EPROM, except in the 2691, where the startup configuration is stored in the same Flash device where the boot code is loaded.

    http://www.cisco.com/en/US/products/hw/routers/ps259/products_tech_note09186a0080094e92.shtml#nvram

     

  • Yes, it's platform specific & may differ in the various models/series. So, some of the older routers might have such an architecture, not on all the series.

  • I suppose the term 'NVRAM' got stuck in software, as hardware evolved into newer technology

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