OK we do it "right" and install RJ45 for the network and RJ11 for the phones.

The customer can STILL plug the phone into the RJ45. So simply providing RJ11 jacks doesn't make it fool proof.

There are also any number of phone systems the use RJ45 jacks for the phones. If you only have RJ11 then those systems are ruled out.

Since the system cannot be fool proof I still vote for the versatility of using RJ45 everywhere.

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Regards the CAT5, CAT6 labels on the jack - that depends. I have some that have no label and some that are label GIGAMAX (or something like that). Granted most of them I've seen have CATx but not all.