I understand the risks of using third party ram but paying for the Cisco branded memory modules and CF cards on an old ASA which is no longer covered but Smartnet is ludicrous.

There are plenty of third parties who claim they sell compatible RAM. Does anyone have any experience as to what memory the ASA 5520 or any of the 55x0 series is compatible with?

  • speed (PC-xxxx or DDR-xxxx)
  • type (regular, ECC, buffered..etc)
  • sizes: (512, 1Gb, 2Gb DIMMS)
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
    – Ron Maupin
    Jan 5, 2021 at 2:37

3 Answers 3


Assuming it's a real 5520 and not a fake that's actually a converted 5510 (yep, a bunch of those were floating around - you'll know it by the fact it's only got a single RAM slot) you'll want PC3200 with CAS latency (CL) of 3 running at 400MT/s, unbuffered, ECC.

Not sure if the ASAs are also picky about the chip arrangement too, so if you want to play it super safe, make sure the RAM you buy has the memory spread across 8 chips.


The ASA's aren't commodity PCs. As such, they aren't as robust or forgiving, and are insanely picky about memory. Even if you think you have all the variables correct, you can still miss one.

I've seen 3rd party memory work in one device, but not another, memory that appears to work until the ASA is software rebooted, etc. It's very telling that Crucial, who makes modules for just about everybody and everything, doesn't list any ASAs. Memoryx lists "certified" (they promise they'll work) modules, but wisely doesn't tell you the exact specs.

  • On the other side of the coin though, ASAs ship with memory from a variety of B-shelf vendors. It's not like it's even labelled as Cisco memory, which they would do if it was 'special'.
    – pboin
    Jun 4, 2013 at 20:35
  • 2
    Not "special", just "tested, and we know these will work."
    – Ricky
    Jun 4, 2013 at 20:42

Just wanted to note about the 2x ASA 5520's that I have. The original sticks inside the 5520s were OEM RAM.
One set had the model/part-no cis00-21077-508mg on it. (PC2700 ECC)
The other was OEM Micron memory mt8vddt6464ay-40bf4 (PC3200 ECC CL3)

As these firewalls are more for testing and lab use now so we chose to take the risk with non ECC memory in order to save money. We found some old server RAM in the warehouse and upgraded each firewall with 4x 512Mb PC2700 non-ECC sticks. Both firewalls booted up fine and have been upgraded to the latest 8.4(6) ASA code. So far they have ran without problems.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.