Recently I needed to do some tests on some Cisco lab kit I have access to. The tests were with full BGP feeds – which cannot be handled by the lab routers due to minimal memory specifications. I set about investigating the memory upgrades and was shocked (again!) at the price of real Cisco RAM. More worryingly, some of the on-line shops I looked at did not convince me they were selling genuine Cisco RAM rather than “compatible”.

Anyway, I decided to look into getting “compatible” memory since these are lab routers, out of warranty and are not under SmartNet contract. Your mileage may vary with this information and you may invalidate your SmartNet or warranty status. That said…

I needed to upgrade Cisco 1801, Cisco 1841, Cisco 2801 and Cisco 2811 routers.

The 1801 went simply from 128MB to 384MB with a Crucial memory SO-DIMM part CT3264X335. The 1801 takes a 200pin SO-DIMM DDR 2700, CL2.5, Unbuffered, Non-ECC, DDR333 memory module. A slower DDR DIMM module may work, but this DDR2700 one worked for me.

The Cisco 1841 took 144pin SDRAM SO-DIMM, PC133, non-ECC, unbuffered. This is the same as the 2801.

The Cisco 2801 takes 144 pin SDRAM SO-DIMM, Unbuffered, non-ECC, PC133. A list of compatible parts should be: KVR133X64SC3/256, MT8LSDT3264LHG-133, THLY25N01C75, CT32M64S8W7E, HYS64V32220GDL-7, MH32S64PFJ6L, EBS26UC6APS-75, HYM72V32M636BT-6, THLY25N01B75, NT256S64VH8A0GM-75, MT8LSDT3264HG-133

The 2811 can be upgraded from 256MB to 512MB or 768MB. The router takes 184-pin unbuffered, ECC, DDR PC2700 ram. I initially tried a Crucial part (CT6472Z335 which was a module MT9VDDT6472AY-335F1) which did not work. The MT9VDDT6472AY is a single rank 512MB module. I then tried a dual rank 512MB module (KVR266X72C2/512) which worked. I would expect MT18VDDT6472AG or similar (with 18 modules rather than 9 modules) dual rank 512MB module to work.

During this investigation and upgrade, it would appear that the 2500, 2600, 3600 take the same flash modules too. They do support different flash module sizes, but realising that the modules are compatible makes troubleshooting or replacing parts simpler. Of course, you have to re-flash the appropriate IOS!

Hopefully this will help someone out there! Of course, using non-Cisco memory may get you into hot water if you ever ring Cisco for support! You have been warned.

10 thoughts on “Cisco router memory upgrades

  1. Thank you for posting this! I just bought a 2811 from my home studies off ebay and needed to upgrade it from 256mb to at least 512mb!

    VERY useful… I’ve just ordered a Kingston KVR266X72C2 ECC module. You’ve saved me a LOT of hassle, thanks again!

    Reply
  2. I ordered the KVR266X72C2/512 module to upgrade my 2811 and it didn’t work. The router immediately says “ERROR: Unsupported DIMM memories in DIMM SLOT:00000001” when powered on. I tried it by itself, and it both slots. No dice. So perhaps not all 2811s are created equal.

    Reply
  3. Howard I have the same issue, the above module didnt work, same error in both DIMM Slots. I have three 2811s and all three have the same error…

    Reply
  4. Using Kingston value ram module KVR266X64SC25/256 (PC2100) worked for me to upgrade Cisco 1801 ram memory from 128MB to 384MB.

    Reply
  5. Hey guys, great info here just wanted to add something.

    Just tried fitting my my 1801 (Annex A ADSL no WiFi model) with a
    512MB Apacer module P/N: 78.92033.111 (PC2700 CL2.5 UNB)
    and to my astonishment it seems to have registered the entire amount.

    The console is a little confused, showing more available than total:
    Cisco 1801 (MPC8500) processor (revision 0x400) with 557056K/98304K bytes of memory. Processor board ID FHK103120BX, with hardware revision 0000

    But, Cisco SDM 533/640MB.

    As yet i’ve been unable to generate enough load to see if it will actually utilize all that it can see, I may try an IOS designed for a unit with 256mb and report back later.

    -Jim

    Reply
    • Hi,

      I believe the 1801 and possibly other 18xx routers have 128MB on the motherboard. Hence the output of 557056K/98304K = total 655,360KB = 640MB = 128MB (on board) + 512MB (DIMM).

      Thanks for the feedback!

      Regards,
      Mike

      Reply
  6. Hi Mike,

    I was just surprised that it went over the stated maximum of 384mb – I was expecting it to only recognize half of the SODIMM.
    Your explanation of the console output is handy, however, I thought it was showing free/total not expansion/onboard.

    At any rate, though I haven’t tried pulling a full BGP, I can’t seem to load the device up to the point where it exceeds ~350mb memory usage, even with a 15.x IOS.

    This I’m guessing indicates either
    a) the extra memory, though visable is not addressable by the unit, or
    b) it will simply never try to use more than that by design, because of its stated maximum.

    At any rate, at least we know a 512mb dimm will work in some fashion.

    Sorry for miffing the HTML tag in the above post – it was late and it looks like I forgot to close it 🙂

    Reply
  7. Thanks for the great info, it saved me a lot of searching and trial and error. I got an 1801 today, and expect three 2811’s to arrive tomorrow.

    Given your info, I found a Kingston KVR333X64SC25/256 in my ‘salvaged memory collection’ and it worked in the 1801. I was so lucky that it was actually the first stick I looked at, out of a few dozen potential SODIMMs in the drawer!

    Reply

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