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which redundancy mode between two sup720-3B with different memory

I have a R7600 with one active sup720-3B(512MB SP and 512MB RP Memory). So can I install one more sup720-3B(1GB SP and 1GB RP) for standby role? And which redundancy mode (RPR, RPR+ or SSO) when I install both supervisors on R7600?

Reza Sharifi
Hall of Fame Expert

In order for SSO to work, you need the have the same exact hardware on both Sups. Even if you get it to work with mismatch memory, it will take the lowest common denominator, which is 512 and 512.


I have the following SUPs, will I be able to do redundancy?  Will I be able to upgrade the firmware?

5    2  WS-SUP720-3B       Hw : 5.6
                                           Fw : 8.5(2)
                                           Sw : 12.2(33)SXI12
                                           Sw1: 20.1(1)SXI9
          WS-SUP720             Hw : 3.1
                                           Fw : 12.2(17r)S4
                                           Sw : 12.2(33)SXI12
          WS-F6K-PFC3B      Hw : 2.3

6    2  WS-SUP720-3B       Hw : 5.8
                                           Fw : 8.5(3)
                                           Sw : 12.2(33)SXI12
                                           Sw1: 20.1(1)SXI9
          WS-SUP720             Hw : 3.3
                                           Fw : 12.2(17r)SX5
                                           Sw : 12.2(33)SXI12
          WS-F6K-PFC3B       Hw : 2.5

Yes, both Sups are the same.  So, you should be able to upgrade and load the same version of IOS to both Sups and configure SSO for redundancy.


Haihua Rong


RPR if you the images does not match.

RPR+ having same IOS.

SSO having same hardware/software.

Take a look at following URL:

In NSF/SSO mode, one MSFC is active and the other MSFC is in a hot-standby mode. The hot-standby MSFC maintains a constant readiness state by receiving state information from the active MSFC. At any given moment, the standby MSFC may be called on by the supervisor engine to take over the responsibilities held by the active MSFC.

-In the above state, you can still access or session into standby MSFC.

RPR overview in 12.2(18)SXF

RPR is a cold standby mode. When a switchover occurs, the standby MSFC must go completely through its initialization. RPR mode is used primarily for the fast software upgrade (FSU). (See the

"Fast Software Upgrade" section

In RPR mode, the startup configuration is synchronized to the standby MSFC, however, it is not processed in any way until the switchover occurs. The running configuration is not synchronized to the standby MSFC.



  So in my case, two sups will be RPR+ redundancy mode, and I can switchover without causing linecards reloaded?



That it is correct. RPR+ is an enhancement in which the standby supervisor is completely booted and

line cards do not reload upon switchover.


Hi, I am having a similar case with two redundant SUP720-3B with 512MB of RAM

I need to test a 1GB (RP and SP) RAM IOS in order to see if a bug disappear but i only have the memory for one supervisor. If the bug disappear then we will buy the memory for the other supervisor. 

What can i spect from this scenario? 

The documentation refers to IOS mismatch but no to RP and SP memory mismatch.