2821 using more than maximum allowed Flash

Answered Question
Jan 7th, 2010
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According to the specs, the 2821 routers can only use up to 256MB on the Flash.


I have a 2821 with a 1GB card and the router boots up normally.


has anyone experienced or used a 2821 with more than its allowed flash?

Correct Answer by Leo Laohoo about 7 years 3 months ago

ISR G1 (this includes the 1800, 2800, 3800) CF slots can take a maximum of 2Gb Type II CF cards.  It can also take up to 2Gb of USB in any of the two ports (except the 1800).  This includes the 860, 870, 880 and 890 ISR routers.  I've used it up to 4Gb and I am confident to say:  Stick to no more than 2Gb. 


ISR G2 will take up to 4Gb.


Does this help?

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Correct Answer
Leo Laohoo Thu, 01/07/2010 - 13:21
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ISR G1 (this includes the 1800, 2800, 3800) CF slots can take a maximum of 2Gb Type II CF cards.  It can also take up to 2Gb of USB in any of the two ports (except the 1800).  This includes the 860, 870, 880 and 890 ISR routers.  I've used it up to 4Gb and I am confident to say:  Stick to no more than 2Gb. 


ISR G2 will take up to 4Gb.


Does this help?

insccisco Thu, 01/07/2010 - 14:55
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where did you get this info from though?


I will stick then with my 1GB flash for my 2821....

Leo Laohoo Thu, 01/07/2010 - 14:58
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where did you get this info from though?


From experience. 

insccisco Thu, 01/07/2010 - 15:10
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hey seriously, this is what I meant, is this written somewhere? I'm using 1GB Flash right now, but if the specs on the router said 256MB max, then it is because of something right?  what if your experience is been pure luck??  it's the same like overclocking in the good old days

Leo Laohoo Thu, 01/07/2010 - 15:18
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But I am serious.  I have deployed a number of ISR G1s with 1Gb or 2Gb CF and works fine.

Leo Laohoo Thu, 01/07/2010 - 17:11
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Just make sure you format the CF and/or USB first before putting any files into it.

Leo Laohoo Sun, 01/10/2010 - 20:43
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Did it work?

insccisco Mon, 01/11/2010 - 08:58
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I still have a 2821 with a 1GB of flash on a non-production environment. The limit on this platform is 256MB, so it is a perfect test, but once again it's only running on non-production environment.


So far I do not see anything wrong with it. On reboots, the IOS does not complaint or anything. So, so far you're right. However, it's not like i don't trust you but I will still need to look deeper into it, then open a TAC case and then make a decision. I need to be 200% sure before I put something like this into production. I've seen and heard of cases (not identical) where for example the IOS version was bigger in size than the minimum required RAM but it worked. The customer continued to let it run but at the end, the IOS expanded and took down the network. I guess they enabled a certain feature which expanded and the router didnt have the required min. RAM for the IOS version, so it crashed.


I mean not identical, but the moral is that if Cisco pre-set a max. limitation to something, then it is because of something, right?


If you could provide some links to the info about the architecture of the CF slots Type II CF cards, etc, that will be great.


thanks

Leo Laohoo Mon, 01/11/2010 - 13:42
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Alot of people upgrade the IOS without realizing that it's not the CF size you should consider but the RAM as well.  In my network, I use the 2Gb CF as a file server for the switch IOS.


Unfortunately, it's only in this forum where you can find posts about using up to 2Gb CF into ISR G1.  You will never find Cisco documentations of using USB thumbdrives to boot your IOS either.


The Data Sheet for the new ISR G2s support up to 4Gb.  Unfortunately, I am unable to get my hands on one to test the full limitations.  My guess is that the G2s will support up to 8Gb.


Give it a go.  I'd be happy if you can make new discoveries or prove me wrong.  


Part of my "router survival kit" is a 2Gb CF and a 2Gb USB thumbdrive.  Both contains identical files of router IOS, ROMmon, WLC firmwares and switch firmwares.

Leo Laohoo Tue, 01/12/2010 - 19:45
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Router uptime is 4 minutes
System returned to ROM by reload at 14:10:37 AEDST Wed Jan 13 2010
System image file is "usbflash0:c2800nm-advsecurityk9-mz.124-7g.bin"


Leo Laohoo Tue, 01/12/2010 - 19:46
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2Gb CFDirectory of flash:/

1  -rw-    38187152  Jan 13 2010 14:37:56 +11:00  c2800nm-advipservicesk9-mz.124-25b.bin

2016968704 bytes total (1978761216 bytes free)

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