There is no exact range, also not for the MR-range. It all depends on your environment. But at least when I was using the internal wireless of the MX64W, it was not that good as I was hoping. This, together with the fact that the MX/Z-wireless is quite limited and does not integrate with MR, I always plan for MXes without integrated wireless and add a small MR access point like the MR36 to the network.
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