|
A modem is a very simple device that does little more than terminate the line and convert the data stream from one format to another (e.g. DOSIS to ethernet or whatever.) It would be highly unusual for a modem to include things like Wi-Fi Access Points and ethernet switches. Such things are usually (and also incorrectly) called "routers," though they are to hell and back different to what an IT professional would know as a router. In the UK, some of the ISP's are rebranding their "routers" to things like HomeHub" and "Superhub" and so forth.
Also, in the UK, some of these "SuperHubs" etc have a "modem only" mode which defeats all but one of the ethernet ports, suppresses the AP and disables the routing functions, etc.
In the "Using Two Routers Together" FAQ pinned in this forum, there's a block diagram that describes (roughly) the internals of a typical SOHO "router" (AKA SuperHub, homeHub, etc.) albeit one without a modem stage.
Having multiple Wi-Fi AP's physically close to each other is not particularly a problem as long as they are not tuned to the same or similar radio channels. The situation isn't fundamentally any different to the process of channel planning for more distant devices. Even when they are physically close and tuned to the same channel, the Wi-Fi protocols have some "good neighbour" mechanisms that kick in when the RSSI's get above certain thresholds to try and prevent them tripping over each other.
By way of examplar, when equipping something like a function room or a meeting hall (or in my case lecture theatre) where one expects there to be many devices, we often deploy multiple AP's to reduce the contention ratios (number of clients per AP) even though a single AP would adequately "cover" the physical space. Though even so, we'd tend to space them out a bit unless there was no other choice. Typically in that scenario, we'd also "fix" the channel plan rather than let it auto-tune.
If you want to use your old router as a second AP, there's a few hoops to jump through in order to get it working. It's described in the aforementioned "Using Two Routers Together" FAQ. Though IIRC we don't delve into channel planning in that FAQ (and SOHO gear doesn't "talk" to each other to automatically devise a channel plan as a "managed" enterprise system would.)
The only way to ensure devices don't hop between your AP's (or "roam" as we usually call it in the business) is to give them different SSID names. In that case, your clients will never roam until they completely loose connection with the incumbent whence the clients will "start from scratch" as if you'd just powered them on.
Or to put it the other way around, if you do want to have your clients roam automatically, the SSID's, passphrases must be the same. Even then, beware of "Big Wi-Fi Myth Number 2" that clients are always "hunting for the best signal" - in fact they do not and some need it to get pretty grotty before they consider roaming.
A lot of client devices create a kind of "profile" for each Wi-Fi SSID they have ever used and sometimes these profiles are maintained in an list in order of preference. You could have a look at your clients and see if they have such and will allow you to manipulate the order of the list (e.g. Windows avails this.)
One "trick" you can use to prevent a client joining a particular SSID is to let it find it and form such a profile then do things like, demote the profile to the lowest ranking and/or "corrupt" the profile so that it will never succeed in making a connection - e.g. make sure the passphrase is invalid. Some clients will allow you to determine whether a particular profile is used automatically or require manual intervention (again Windows as the e.g.) there is a setting in each profile (on by default) to "automatically connect when network is in range" or words to that effect, so simply just untick it. |
|