I'm a student that will be taking my CCNA exam in early June and I'm doing a lot of practical revision, I tend to get sidetracked by little things such as this question I'm about to post. It's regarding flash and nvram. The terms are sometimes used interchangeably even though they are two different things. For instance, from this Cisco link: http://www.cisco.com/en/US/products/hw/switches/ps5213/products_tech_note09186a0080a49dbf.shtml
VTP client and server systems require VTP updates from other VTP servers to be immediately saved in NVRAM without user intervention. The VTP update requirements are met by the default CatOS operation, but the Cisco IOS software update model requires an alternative update operation. For this, a VLAN database was introduced to Cisco IOS software for Catalyst switches as a method to immediately save VTP updates for VTP clients and servers. This VLAN database is in the form of a separate file in NVRAM called the vlan.dat file.
And then later in the same article, it adds some context to which systems use different terminology:
*The vlan.dat stored in NVRAM alone can be accessed by the switch. The vlan.dat file can be copied from its location for backup purposes. The memory location name where the vlan.dat file is stored varies from device to device. Refer to the respective product documentation before you issue the copy command.
In Cisco Catalyst 6500/6000 series switches, it is const_nvram:. Similarly for Catalyst 4500/4000 switches, it is cat4000_flash:. In Cisco Catalyst 29xx series and Cisco Catalyst 35xx, 3750 series, it is referred to as flash:.*
So what the documentation here tells me that:
6500/6000 series switches: NVRAM = const_nvram:
4500/4000 series switches: NVRAM = cat4000_flash:
29xx, 35xx, 3750 series : NVRAM = flash:
And, by Ciscos definition if NVRAM = flash, on a 2960 switch, then yes, the vlan.dat is stored in the NVRAM and what the documentation says is correct. But what about the other NVRAM? the one where the startup-config is stored, that's a different NVRAM entirely! What is going on here?
My problem is, a lot of the time if I'm reading something for the first time, I can never be sure if they are referring to the real NVRAM where the startup-config is stored, or the Flash memory where the IOS is stored (and vlan.dat). It seems to me that they are moving to migrate both flash and nvram? (nvram and const_nvram in the latest series?) I mean, functionally wise, nvram and flash are the same. Writable memory that doesn't wipe after a reload.
But yes, my question. Is there any general guidelines or rules that I should use for interpreting whether or not to read 'flash:' when they actually say nvram?