Hello,
1. With dual SUP VSS (one SUP in each catalyst), if one SUP died the other SUP will take over the control plane, does the data plane would be active on both Catalyst in this scenario?
Yes. With full-mesh physical path between both virtual-switch chassis, the network availability is maintained until the failed chassis is restored.
2. Do you have uptime / reliability figures with Dual SUP vs Quad SUP?
The answer really is "it depends". Network deployed in best practices protects network avaiability, deploying Quad-sup helps protecting network availability and the capacity if one of the supervisor is impacted with major fault & it fails to recover. In this case, the standby supervisor restore the impacted chassis with the normal bootup time which varies based on how number of modules installed in chassis, topology size etc.
3. Does the support of ISSU depends on Quad SUP or the IOS trail i.e., SXI?
6500-VSS supports Enhanced Fast Software Upgrade (eFSU) from the user front-end the upgrade procedure is same as ISSU. Following same procedure it gracefully upgrade two or four supervisors between two different chassis.
Please refer to Chapter 2 and 4 that provides detail design and deployment guidance of VSS dual and quad-sup...
http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/Borderless_Campus_Network_1.0/Borderless_Campus_1.0_Design_Guide.pdf
thanks,
rahul.
