Cisco 1600 series routers from Cisco Systems have two memory architectures: run-from-Flash (RFF) and run-from-RAM (RFR). Router model names with an R (such as 1601 R) are RFR routers; all other models are RFF. In this document, model names without an R refer to both RFF and RFR models, except where noted. This document describes the two memory architectures used in the Cisco 1600 series routers.
With RFR, the Cisco IOS® software image is stored in Flash memory (usually in compressed form), but is loaded into RAM before being executed by the router. Because the running software image then resides in RAM, a new software image can be downloaded and copied over the software image stored in Flash memory.
In RFR routers, only a minimal boot-helper image is stored in the ROM for disaster recovery (such as the Cisco IOS software image in Flash becomes corrupted). Initial loading of a software image into Flash memory is done over the console port or the local Ethernet port.
Because the Cisco IOS software image is stored in compressed form in Flash memory and then decompressed when loaded into RAM, the standard configuration for the RFR models contains less Flash memory but more DRAM than the RFF models.
With RFF, the router executes the uncompressed Cisco IOS software image stored in Flash memory. RAM stores working data such as Cisco IOS data structures, network routing tables, and packets to be transmitted to and received from network interfaces.
The running software image cannot be used to download new software to Flash memory because it would attempt to overwrite itself. (However, when you are using Dual Flash Bank memory, you can download the new software image into a different Flash memory partition.)
To download a new software image without using Dual Flash Bank memory, a boot-helper image (called XBOOT) has been added to the ROM on the RFF models. The boot-helper image is a small subset of Cisco IOS software that supports only a subset of the WAN interfaces and the protocols. RFF ROM supports the following WAN interfaces. (These are all onboard interfaces, not WAN-interface-card interfaces.)
- Serial (synchronous and asynchronous) (Cisco 1601)
- Digital service unit/channel service unit (DSU/CSU) (Cisco 1602)
- ISDN S/T (Cisco 1603)
- ISDN U (Cisco 1604 and Cisco 1604 R)
When upgrading the Cisco IOS software in Flash memory, you must boot the router from the ROM image. The Flash memory can be overwritten because the Cisco IOS software that is stored in Flash memory is not being used to run the router. Table 1 is a summary comparison of these two memory architectures.
|Feature||Run-from-Flash Routers||Run-from-RAM Routers|
|Cisco IOS Software Online Download||
Yes, when using Dual Flash Bank memory
|Flash Memory Use||
|Flash PC Card Capacity||
|Disaster Recovery (Router Fails and Image Store in Flash Memory Is Corrupted)||
Use the Cisco IOS "show version" command to display some memory architecture information for your router (show in boldface in the example output):
- Amount of onboard DRAM (a type of RAM)
- Whether the Cisco IOS software is running from RAM or Flash memory
- Amount of Flash memory
Router#sh ver Cisco Internetwork Operating System Software IOS (tm) 1600 Software (C1600-BNSY-M), EARLY DEPLOYMENT RELEASE SOFTWARE 11.2(9)P Copyright (c) 1986-1997 by cisco Systems, Inc. Compiled Mon 11-Aug-97 14:10 by claux Image text-base: 0x02005000, data-base: 0x02477BD0 ROM: System Bootstrap, Version 11.1(12)AA, EARLY DEPLOYMENT RELEASE SOFTWARE (f) ROM: 1600 Software (C1600-RBOOT-R), Version 11.1(12)AA, EARLY DEPLOYMENT RELEASE Router uptime is 12 minutes System restarted by power-on System image file is "flash:c1600-bnsy-mz", booted via flash cisco 1605 (68360) processor (revision C) with 7680K/512K bytes of memory. Processor board ID 06027889, with hardware revision 00000000 Bridging software. X.25 software, Version 2.0, NET2, BFE and GOSIP compliant. 2 Ethernet/IEEE 802.3 interface(s) System/IO memory with parity disabled 8192K bytes of DRAM onboard System running from RAM 8K bytes of non-volatile configuration memory. 4096K bytes of processor board PCMCIA flash (Read/Write) Configuration register is 0x2102