The system is currently on R9.1 and the customer wants to upgrade to R11 (although they still use 5410 phones), which I've read on here have issues with R11 (although seem to be ok on R10.1).
If they do get issues, will they be able to use those R11 specific licences on R10?
If they do get issues, will they be able to use those R11 specific licences on R10?