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New Member

SSO hardware requirement

Dear all,

I want to upgrade SUP 720 DRAM in 7609. Existing are both have 512 Mb of SP and RP. The redundancy mode is SSO and its currently working okay now. I plan to upgrade the standby SUP DRAM first to 1Gb, and then force the router to switchover. And after that, will I continue to upgrade the previously active SUP memory to 1Gb. my question is, after I upgrade the standby SUP, the hardware of those SUPs will be different right? (the active has memory of 512, the standby has memory of 1Gb) So, will SSO work in condition like this?

New Member

Re: SSO hardware requirement

Hi Prima,

Cisco IOS software running on the supervisor engine and the MSFC supports redundant configurations when the supervisor engines and MSFC routers are identical. If they are not identical, one will boot first and become active and hold the other supervisor engine and MSFC in a reset condition.

Hope to help,


New Member

Re: SSO hardware requirement

Yeah, i know on the requirement the supervisor engine and MSFC have to be identical. But, does that mean the memory or the flash inside the supervisor have to be the same also or only the type of the SUP and type of MSFC have to be the same?

I actually gonna try this, I'll let you know what the result is.

Hall of Fame Super Silver

Re: SSO hardware requirement

Hello Prima,

the SSO protocol should exchange information about the MSFC and supervisor models and IOS version in use in the two supervisors.

If the info about the amount of memory is not exchanged it cannot be compared.

in the installation guide for memory upgrade there is no reference to SSO scenarios')">

But of course only the test can say what happens.

Hope to help


New Member

Re: SSO hardware requirement


I have tried SSO using 2 SUP but with different DRAM (the active SUP720 has 1Gb, the standby SUP720 has 512Mb). It worked. I have tried to switchover using "redundancy force-switchover" command, and the active SUP moved from one to another. I think this mean that the SSO was working. The question is: is it actually working as it suppose to work? I mean, if the active SUP has say 500,000 routes and uses 600Mb of memory to store this routing table on the DRAM, what will happen if it switchover to the standby SUP that only has 512Mb of RAM??? The switchover process maybe done successfully, but there's a strong chance the router losses some routes. Any thought?



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