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On a Mac open System Preferences, click Network, click Wi-Fi, then click the Advanced button. In the list of Preferred Networks you can drag them to the order you want them to connected. For example I have my 5GHz network at the top of the list and the 2.4GHz below it.
iOS isn't so easy. Apparently you can do it with a Configuration Profile. Also read this Apple article: How iOS decides which wireless network to auto-join.
Thanks, but I already knew about the Mac side. I was hoping for a way to do the equivalent on iOS. We have two networks, and iOS usually grabs the one we don't want first, so we have to keep manually switching it.
 


I don't know about other modems/routers, but mine (from Comcast) will not let me establish the two networks with exactly the same SSID.
This varies from model to model. My Zoom cable modem is single-band and supports up to four networks (one primary, three guest) on the 2.4GHz band. My other access points (Linksys routers in bridge mode) support two networks each - one on each band. I can, and do, use the same SSID for both.
Recently while at my daughter and son-in-law's place, he was complaining about the slowness of his connection. He was getting less than 50 mb/s while I was getting close to 200 mb/s. After checking his network(s), I figured out that my computer was connecting to the 5 gHz while he was connecting to the 2.6 gHz. The simple change to the 5 virtually doubled his speed. And a couple of other tweaks got him to around 150 mb/s.
This is going to depend on the channel width and congestion on the selected bands.

Based on my configuration options (other devices may be different), I can select different channels for each band, and I can select 20 or 40MHz bandwidth centered on the chosen channel. 40MHz (802.11n only) gangs together two channels for higher bandwidth, when the client devices are compatible, but may be subject to more interference - especially on the 2.4GHz band, where channels already overlap by quite a bit.

Because both bands offer the same choices (bandwidths) for each channel, there is nothing inherently faster about 5GHz vs. 2.4GHz. But there is less chance for interference in the 5GHz band, because the channels do not overlap at 20MHz bandwidth and don't have near as much overlap at 40MHz, and there are, in general, fewer 5GHz hot-spots to interfere with yours.

If your 2.4GHz networks have so much interference that your devices are being cut down to 1/3 of their proper speed, then you might want to try selecting a different channel. There are tools (like iStumbler) that you can use to scan for networks to help select a channel without as much congestion. Hopefully, there will be a choice better than the one you are using at this time.
 


Because both bands offer the same choices (bandwidths) for each channel, there is nothing inherently faster about 5GHz vs. 2.4GHz. But there is less chance for interference in the 5GHz band, because the channels do not overlap at 20MHz bandwidth and don't have near as much overlap at 40MHz, and there are, in general, fewer 5GHz hot-spots to interfere with yours.
One other variable that may account for slower performance on the 2.4GHz band is maintaining compatibility with older/slower devices that use 802.11b or g. I believe connecting a device using b or g will bring down the performance of all devices connected to the same channel to that level, and 802.11g is limited to 54mb/s. This is not a concern at 5GHz, because 802.11b/g are only supported at 2.4GHz.
 


On a Mac open System Preferences, click Network, click Wi-Fi, then click the Advanced button. In the list of Preferred Networks you can drag them to the order you want them to connected. For example I have my 5GHz network at the top of the list and the 2.4GHz below it.
It's my understanding that if you use iCloud Keychain, as you delete or sort the order of Wi-Fi networks on your Mac, those changes will propagate to your iOS devices that use the same iCloud Keychain. Does anyone know if this is definitely the case?
iOS isn't so easy. Apparently you can do it with a Configuration Profile. Also read this Apple article: How iOS decides which wireless network to auto-join.
Thank you for posting this link - I hadn't seen that info published before. Following a link at the bottom of that page took me to About wireless roaming for enterprise, where I learned that Airport Utility on iOS has a hidden Wi-Fi Scan feature that can be enabled in settings.
 


I don't know about other modems/routers, but mine (from Comcast) will not let me establish the two networks with exactly the same SSID.
I thought I had the same problem on my CenturyLink router. However, I found that if I set the 5GHz radio SSID first, then I can also set the 2.4GHz SSID to the same. Just not in the reverse order.

I tried a TP-Link Deco mesh system, and found it impossible to turn off both my CenturyLink Wifi radios (2.4 and 5GHz). Tech support sent me to an odd settings page where I disabled a security setting that was hardly relevant to this, but then I was able to disable both radios. Unfortunately, the Deco M5 units were complete failures and I went back to the CenturyLink modem/router/Wifi unit. That single unit provides me with nearly 100 Mb/s WiFi within 20-30' and poor signal 60' away in a back room. The mesh units typically provided under 50 Mb/s everywhere (even 5' from the main unit connected to the modem), when they stayed up at all. I think I'll try an ethernet backhauled WiFi bridge in the back room. (I'm open to suggestions.)
 


One other variable that may account for slower performance on the 2.4GHz band is maintaining compatibility with older/slower devices that use 802.11b or g. I believe connecting a device using b or g will bring down the performance of all devices connected to the same channel to that level, and 802.11g is limited to 54mb/s. This is not a concern at 5GHz, because 802.11b/g are only supported at 2.4GHz.
Not quite. Having an 802.11b or g device will not cause your "n" devices to run at 11Mbps (or 54Mbps, respectively). The router does not drop down to "compatibility" speeds, forcing everything else down with it.

What actually happens is the router will dynamically change speeds as its packet flow switches between your devices. So it will run at 802.11b for a "b" device and it will switch to 802.11g for a "g" device or 802.11n for an "n" device.

The reason people say a slow device can slow down your network is because faster devices have to wait for the slower devices. If a "g" device takes 10 seconds to download a file, a "b" device will take about 50 seconds to download that same file. The "b" device will be monopolizing the Wi-Fi channel during that time, blocking out all other devices.

So if, for example, you have a mix of "b", "g" and "n" devices on the same band, transferring a similar mix of data, the slower devices are going to be consuming a disproportionately large percentage of time during which the faster devices have to wait. But when they actually have the air interface, the fast devices will transfer data at their maximum speed.

This also means that a "b" or "g" device that's connected to the network but mostly sitting idle is not going to have a noticeable impact on throughput. But if it starts to move a lot of data, then there will be an impact.
It's my understanding that if you use iCloud Keychain, as you delete or sort the order of Wi-Fi networks on your Mac, those changes will propagate to your iOS devices that use the same iCloud Keychain. Does anyone know if this is definitely the case?
The keychain definitely propagates. When I check the list of Wi-Fi connections on my Mac, I always see the ones that my phone and iPod have used. Deleting a connection from the Mac also removes it from the other devices. Credentials (passwords, etc.) propagate with the keys.

What I don't know is whether iOS respects the preference-order that's stored in the keychain or if it just treats them as an unsorted collection, applying its own preference algorithm to the collection.
 


Not quite. Having an 802.11b or g device will not cause your "n" devices to run at 11Mbps (or 54Mbps, respectively).
That's fascinating. Thank you, as always, for an informative explanation that is understandable by non-expert users such as myself.

Do you know how a Wi-Fi network can be expected to perform if it has a mix of 802.11g and 802.11n devices, where an 802.11g device is transmitting packets continuously, such as a Wi-Fi enabled camera?
 


... I learned that Airport Utility on iOS has a hidden Wi-Fi Scan feature that can be enabled in settings.
Thanks for that, I didn't know about it. I just tested it and found more Apple hypocrisy. According to the developers of several iOS network utilities I use, Apple will not allow them to display any device's MAC. Yet Apple's AirPort Utility showed me the MAC of every WiFi router, regardless of manufacturer.
 


Do you know how a Wi-Fi network can be expected to perform if it has a mix of 802.11g and 802.11n devices, where an 802.11g device is transmitting packets continuously, such as a Wi-Fi enabled camera?
It's going to be a function of how much data it is transmitting.

If an 802.11g camera is trying to broadcast a full 54Mb/s, then it could theoretically end up consuming all of the bandwidth, leaving nothing for any other devices. One would hope that the router and devices will implement some kind of congestion control to divvy up the bandwidth fairly (e.g. give each device half of the air-time, limiting the "g" device to 27Mbps and the "n" device (assuming only one) to half of its maximum - which could be anywhere between 27 and 300Mbps depending on hardware, configuration and signal clarity).

Assuming your camera is broadcasting at a more reasonable data rate (and assuming you know it is actually getting that rate), you should be able to divide that rate by 54Mbps to determine what percentage of air-time the camera is consuming. The remaining percentage of the time will be available to other devices, at their own respective data rates.

But even that's just going to be a ball-park estimate, because there can be (probably will be) interference in the air - from other Wi-Fi networks, non-Wi-Fi devices using the same band, and good old-fashioned random EMI. And your different devices may be affected differently by the interference, due to use of different protocols, different hardware and different physical locations.

Ultimately, you would need to take measurements to determine the actual amount of bandwidth consumed by each device.
 


Thanks to Michael, Ira and David for replies. Been a crazy week, but I will tackle our printer network problem over the weekend and report back to this thread with results -- hopefully with success.
I think I solved the problem with both Brother printers by using the "reset the network" and/or "setup wizard" commands. This allowed me to set up both printers with no prior settings lingering around. I selected the correct network from the three in our house, reentered the appropriate password, and everything seems to be working just fine. My earlier attempts to go right to passwords on each printer, as well as deleting and reselecting printers from the macOS Printers and Scanners prefs, did not work. I had done this repeatedly, assuming doing the same thing over and over again would get a different result (!).

Thanks for all the suggestions. My next step would have been to use a specific address on the WLAN for each printer, but as one commenter said, this may have bounced the printers back off if the router gets reset again (such as with a power failure).
 


Did you change any software, including the macOS? I have an old Brother MFC-8860DN, which still works perfectly after fourteen years. Brother says the printer is not supported under the last couple of macOS iterations, including Sierra (which I am using now). Mine keeps working, but although I have updated the OS over the previous OS several times, I never reinstalled any of the Brother software on my Mac.
 


I don't know about other modems/routers, but mine (from Comcast) will not let me establish the two networks with exactly the same SSID.
Is it possible you have an older model? My Comcast supplied modem/router does allow this. It has been my experience with Comcast that you can take the box to a local office and exchange it, or call them and they will mail you one.
 


Did you change any software, including the macOS? I have an old Brother MFC-8860DN, which still works perfectly after fourteen years. Brother says the printer is not supported under the last couple of macOS iterations, including Sierra (which I am using now). Mine keeps working, but although I have updated the OS over the previous OS several times, I never reinstalled any of the Brother software on my Mac.
We bought both printers about 6 years ago for our consulting business and have upgraded both Macs and OS's since then. My 2017 27-inch iMac is running High Sierra, while my wife's 2014 MacBook Pro is running Sierra.

We periodically get auto notices from Apple that a new Brother driver update is available, and we update. No problems up to now, including two moves and -- two years ago -- a new Airport Time Capsule. So... always updated software (including printing apps and Vuescan scanning app), and our recent problem came about with the wireless router reset. After 24 hours, it looks like we are back in business.
 


I have an old Brother MFC-8860DN, which still works perfectly after fourteen years. Brother says the printer is not supported under the last couple of macOS iterations, including Sierra (which I am using now). Mine keeps working, but although I have updated the OS over the previous OS several times, I never reinstalled any of the Brother software on my Mac.
According to the spec sheet, this printer is a "Windows GDI" printer that includes emulations for (among other things) PCL6 and PostScript 3. If this "emulation" is built-in to the printer's firmware, then even if the old drivers stop working, you should be able to use generic PS or PCL drivers forever. If the emulation is not in the printer but is part of the driver, then you might be out of luck should they stop working in the future.

The real lack of support here is likely to be for the scanner and PC-FAX features. But you may not actually be using these features. And you should always be able to scan to FTP or e-mail, since that doesn't require any drivers.
 


According to the spec sheet, this printer is a "Windows GDI" printer that includes emulations for (among other things) PCL6 and PostScript 3. If this "emulation" is built-in to the printer's firmware, then even if the old drivers stop working, you should be able to use generic PS or PCL drivers forever. If the emulation is not in the printer but is part of the driver, then you might be out of luck should they stop working in the future.
The real lack of support here is likely to be for the scanner and PC-FAX features. But you may not actually be using these features. And you should always be able to scan to FTP or e-mail, since that doesn't require any drivers.
I think Vuescan supports just about any legacy scanner, and, in my opinion, is great software.
 



I tried a TP-Link Deco mesh system… Unfortunately, the Deco M5 units were complete failures and I went back to the CenturyLink modem/router/Wifi unit. That single unit provides me with nearly 100 Mb/s WiFi within 20-30' and poor signal 60' away in a back room. The mesh units typically provided under 50 Mb/s everywhere (even 5' from the main unit connected to the modem), when they stayed up at all. I think I'll try an ethernet backhauled WiFi bridge in the back room. (I'm open to suggestions.)
I've been using that kind of system for about three years with my now-ancient Airport Extreme and Airport Express setup. I don't have any Ethernet cable in the walls, but I do have coax cable in nearly every room, and a TiVo that uses MoCA to connect to a remote box in our bedroom. I've leveraged it to have an Ethernet connection to my office iMac. I hard-connect the Airport Express from the office Ethernet hub, and that's enough to give me good, fast WiFi throughout the house.

MoCA is pretty simple. At the main router, you connect an adaptor to your cable modem (with a coax splitter) and to your router on an Ethernet port. You also need a Point of Entry (PoE) filter between your cable coax main entry point and the street to keep your network from being accessible to everyone on your local Internet node. At cable outlets in other parts of the building, you install another splitter (if you are using the outlet for TV as well) and an adaptor. You'll want to hang a small Ethernet hub from the adaptor, or (as we did in our bedroom) install a switch that includes a MoCA adaptor.

Not everyone will want to go this route, but for our situation it meant we didn't have to pull any cable, and it's plenty fast.
 



I don't have any Ethernet cable in the walls, but I do have coax cable in nearly every room, and a TiVo that uses MoCA to connect to a remote box in our bedroom.
... for our situation it meant we didn't have to pull any cable, and it's plenty fast.
MoCA has several different revisions of the standard that use different speeds. If you want to use MoCA networking, make sure all your devices run at the same MoCA version. Also make sure all the interfaces are using the same channels.
  • MoCA 1.0 supports one channel at 100Mbit/s
  • MoCA 1.1 bumps the channel speed to 175Mbit/s.
  • MoCA 2.0 and 2.1 bump the channel speed to 500Mbit/s. They also allow bonding two channels together for up to 1Gbit/s
  • MoCA 2.5 supports bonding up to 5 channels for up to 2.5Gbit/s
Unfortunately, because your coax wires will carry more than just MoCA data (e.g. cable or satellite TV), you usually can't link together coax networks from multiple service providers. For instance, I can't have my Dish Network "Hopper" DVR share the same coax network with my Comcast cable modem. The satellite TV and cable TV use different bands and don't interfere with each other, but the Hopper's MoCA (which it uses to communicate with its "Joey" remote set top boxes) is hard-wired to use channels that step all over the cable TV's bands, trashing the cable modem. So the cable modem needs to be isolated on a separate segment of coax and the Hopper needs to use Wi-Fi or Ethernet for Internet access.
 



MoCA has several different revisions of the standard that use different speeds. If you want to use MoCA networking, make sure all your devices run at the same MoCA version.
I thought I read that MoCA was backwards compatible, so you can use adapters with different versions of the spec, but your network would be limited to the speed of the lowest version. It's been a few years since I setup my MoCA network, so I may be wrong about that.
 


I thought I read that MoCA was backwards compatible, so you can use adapters with different versions of the spec, but your network would be limited to the speed of the lowest version. It's been a few years since I setup my MoCA network, so I may be wrong about that.
Yes, but you don't want to cripple your network, mixing revisions. If you have MoCA 2.0 equipment (e.g. FiOS Quantum), then you will want to make sure the rest of your MoCA gear is also 2.0 (or later).
 


I was reading some news sites, when my internet connection (normally 20/20 MB/sec) slowed to a crawl - down to 0.02 MB according to Speedtest. It's not just Safari - Chrome has the same problem. The issue goes away in Safe Mode. I tried reloading the OS, but there is no change. My virus detection (TotalAV) shows nothing, though it catches a lot of adware vermin. Something is hidden somewhere that is causing this, but I can't find anything. Help!
 


I was reading some news sites, when my internet connection (normally 20/20 MB/sec) slowed to a crawl...
... I did solve the problem, and it indicates an odd behavior in High Sierra, macOS 10.13.6, and possibly other versions.

I had my iPhone X connected to my MacBook Pro with a USB cable to sync with iTunes. I had cellular data turned on, and the iPhone always switched from that when I was away from home to my WiFi when I returned. I never turned off cellular data, but it never used it if it had a known WiFi link. When I went to the library, it automatically connected to the library WiFi, as it did everywhere I went.

But when connected to my MacBook, that didn't happen. Instead, it dropped a 20Mbps wifi link and switched to the iPhone's cellurlar data link! Of course that had almost no bandwidth compared to my wifi link. When I disconnected the iPhone, the MacBook Pro instantly switched back to WiFi. That's obviously backward from what it should do!
 


...
But when connected to my MacBook, that didn't happen. Instead, it dropped a 20Mbps wifi link and switched to the iPhone's cellurlar data link! Of course that had almost no bandwidth compared to my wifi link. When I disconnected the iPhone, the MacBook Pro instantly switched back to WiFi. That's obviously backward from what it should do!
Do you have Personal Hotspot explicity enabled on the X?
 


...Instead, it dropped a 20Mbps wifi link and switched to the iPhone's cellurlar data link! Of course that had almost no bandwidth compared to my wifi link. When I disconnected the iPhone, the MacBook Pro instantly switched back to WiFi. That's obviously backward from what it should do!
What is the service order set to?

If you go to "System Preferences -> Network" and then the gear icon near the lower left, there is an option "Set Service Order". It should let you pick the order - e.g. so it picks ethernet over wifi.

I haven't checked to see if it does it with your iPhone's cellular data, but I suspect so.

For example, mine is set to like this so that (in theory) the fastest one is first and slowest is last:
Thunderbolt Ethernet slot 1​
Thunderbolt Bridge​
USB 10/100/1000 LAN​
Wi-Fi​
Bluetooth PAN​

I haven't shared my iPhone connection on the computer yet, but I suspect it will be similar.
 


What is the service order set to? ...
For example, mine is set to like this so that (in theory) the fastest one is first and slowest is last:
Thunderbolt Ethernet slot 1​
Thunderbolt Ethernet slot 1​
Thunderbolt Bridge​
USB 10/100/1000 LAN​
Wi-Fi​
Bluetooth PAN​
I haven't shared my iPhone connection on the computer yet, but I suspect it will be similar.
My understanding is that if you set your phone as a hotspot, it will share your data over WiFi, Bluetooth, or USB. So, under your configuration listed above, the phone over USB will be before Wi-Fi.
 


My understanding is that if you set your phone as a hotspot, it will share your data over WiFi, Bluetooth, or USB. So, under your configuration listed above, the phone over USB will be before Wi-Fi.
That is my understanding, too. I generally don't have USB first, but had a USB ethernet adaptor on there at one point.
 


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