I have a C891FW-E-K9 ISR with ios c800-universalk9-mz.SPA.154-3.M-2. From what I can gather, the memory requirements for that image is 512MB but from "show version" my router seems to only have 384MB which could be the reason why it runs out of memory sometimes.

I am wondering if it's possible to upgrade the memory of the router and if possible, which module would be compatible. When I look for data sheets I find this one: http://www.cisco.com/c/en/us/products/collateral/routers/800-series-routers/data_sheet_c78-519930.html

As far as I can understand the C891FW is the same as C891F but with wireless and the data sheet states that default DRAM is 512MB and upgradeable to 1024MB with FL-8XX-512U1GB.

Why does show version tell me 384MB of DRAM when Data Sheets says 512MB? and is it possible to upgrade RAM of this model?

Thanks in advance!


The 891 has 512MB, the 892 has 768MB - you can upgrade the memory in your 891 to 768MB with part number MEM8XX-512U768D. The 1GB upgrade is for the 892 only sorry.

I suspect the 'missing memory' is just what IOS uses.


The C891FW comes from the factory with 1 GB physically installed on the motherboard, but with only 512 MB enabled. Of this 512 MB, 128 is allocated to (I think) the wireless access point, leaving 384 MB for the core router. In order to enable the remaining 512 MB of RAM, you need to purchase an upgrade license (not a physical memory DIMM). I believe the part number for this upgrade license is FL-8XX-512U1GB.

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