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Community Member

Cisco 1841 router IOS upgrade questions

We currently have a Cisco 1841 router with version 12.4(1c) of IOS using image c1841-ipbase-mz.124-1c.bin.  Our goal is to make it so our router can fully support IPv6. The current IOS version cannot. I've seen a site that seems to indicate 12.4T does support with IP Base image but recently had Cisco tell me with the latest IOS release 15.1.4.M4 that I have to use either the "Advanced Enterprise Services" or "Advanced IP Services" image.  Did Cisco just remove IPv6 from IPBase in later IOS releases?

Also I've seen conflicting specs on the max amount of Flash and DRAM the router can support. The following link shows that 384MB is the max for DRAM and 128MB max for flash. We're looking to upgrade ours from 128MB and 32MB respectively but as mentioned I've seen it where higher amounts are supported. In fact we bought a backup 1841 to have and it has a 256MB Flash card in it.

Last but not least. Where can I find a straightforward documention of this situation where we may have to upgrade our Flash and DRAM and then upgrading the IOS?

VIP Super Bronze

Cisco 1841 router IOS upgrade questions

According to the link, table-5 you provided, the maximum DRAM is 384 and max flash is 128.  Usually for IOS 15, you need a minimum of 256 DRAM and 128 flash.  So if you upgrade to the max, you should be good to go.

DRAM Capacity

• Default: 256 MB

• Maximum: 384 MB

Flash Memory

External compact Flash

Flash Memory Capacity

• Default: 64 MB

• Maximum: 128 MB

Also, have a look at table-2 in this link for the recommended amount of flash and memory for IOS 15.


Hall of Fame Super Gold

Cisco 1841 router IOS upgrade questions

Good point from Reza.

The question I'd like to ask you is WHAT is your WAN link bandwidth.

The reason why I'm asking is because I want to know if it's more convenient to just upgrade the entire appliance to something more recent.

Community Member

Cisco 1841 router IOS upgrade questions


Our WAN link is a T-1.

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