i believe the APs can go four hops. I've seen them go three hops on my own networks. That said, each hop loses significant bandwidth (50% per hop if you are also using the 5 GHz radio to service clients), so you really want to minimize hops.
From a design perspective, I generally follow the following guidelines: - At least 20% of your nodes should be "root nodes", meaning that they have a "wired" connection back to the demarc. This "wired connection" can be Ethernet, fiber, or a WDS bridge link on a different frequency using dedicated link hardware, such as the ZF7731 or the new P300 (or 3rd party). - Your remote nodes should nominally be designed to be one hop away from a root node. This means that your root nodes should be (reasonably) evenly distributed throughout your network. - Your root nodes should be set to fixed and non-overlapping 5 GHz channels. Your remote nodes should auto-channel to find the nearest root node.
This is spot on. I would definitely not recommend more than 3 hops with 802.11n hardware, as in my own experience, a network with 3 hops is no longer able to support even approximately 75mbit of SpeedFlex throughput from the edge back to the ZoneDirector, which is starting to go into the territory of slow wifi.
Another technique worth mentioning that isn't described in some of the older meshing Best Practices guides is the new "eMesh AP" mesh type. Basically, if you wire up an island of outdoor AP's (for example, just wire one T300 into another T300), they will form an eMesh AP, where one AP is a normal mesh node on the same channel as the other mesh AP's, and the other AP gets to pick its own channel and not share airtime, using the wired link to the other AP as the mesh backhaul.
This technique does not result in the full 50% degradation in performance per hop, and might be more practical. If you find performance too slow, it might be worth trying to add an eMesh AP somewhere in the middle of your mesh.
See your ZD's Configure/Mesh page, where you can configure the maximum mesh hop count. We don't recommend over 5 hops, but less is better when you consider that due to the half-duplex nature of wireless, using the same 5G backhaul radios to send/receive, you lose ~50% bw with each hop. We have a best practices guide on Support too.