Double NAT on Airport Express

I've noticed since I put the AE in Bridge Mode that both networks show on the available networks list and both continue to generate WiFi signals. Each has a different name so I wondered if my MBP was switching between them to the strongest signal.

Sorry, I had to step away for a bit so I didn't get to respond sooner. (Thanks Bob for stepping in!)

In a roaming network, the following would be true:

• All wireless routers would need to be interconnected by Ethernet.
• Each wireless router would broadcast their own Wi-Fi network.
• Each Wi-Fi network would use the same network name and wireless security type & password. That way, even though there are multiple Wi-Fi networks operating simultaneously, wireless network clients would "see" them as a single network.

Because, currently, you are "seeing" each wireless network broadcast with a different name, you just need to change the name on either to match. I suggest that you do so with the AE so its network name & security matches that provided by your Comcast gateway.

When using different network names, you would have to disconnect from one network to the other. The wireless clients will typically not automatically switch networks even if one has a stronger signal than the other. On the other hand, when the names are identical, a wireless client should switch automatically ... this the concept of "roaming" is satisfied.

1. Do Airport Express routers deteriorate with age like many routers, possibly slowing down internet speeds? Mine is 5 years old and some say replace it.

Yes and no. Yes, they, like any consumer-grade networking device, will "degrade" over time. The typical lifespan of these are 3-5 years ... and this is not unique to the Apple base stations. However, they do NOT directly affect your Internet speed as that is controlled by your ISP and the current Internet traffic between your gateway and the site you are trying to access.

... but, looking at it from an end-to-end standpoint, you may notice poorer performance overall when using a web-based data rate measurement application, like Ookla's Speed Test. As you can imagine, any weak link between the two points can affect that segment of the connection.

2. I have been running just the AE for wifi placing the Gateway on Bridge Mode. I noticed internet speeds were down between 12 and 25 mbs. Comcast sent a notice that they doubled my internet speeds but when I followed instructions for rebooting the modem to get the upgrade, the speeds didn't change. When I called them, they said the upgrade could be implemented because I was in Bridge Mode. I turned Bridge Mode off on the Gateway and the internet speed tests on the Gateway network significantly increased. I tested the AE network and found they significantly increased as well, but I get the flashing amber light and the Double NAT warning advising me to put the AE in Bridge Mode.

For reference, that AirPort Express base station employs 100 Mbps Ethernet ports. Most likely, your gateway uses 1000 Mbps ports. If, per chance, Comcast increased either your upload or download Internet speeds beyond 100 Mbps, it would be "restricted" by the Express.

When you have two or more routers in series, you typically will always want the downstream router (in this case your Express) to be in bridge mode, leaving routing functions to the "main" router that is directly connected to the Internet.

I tested the AE network and found they significantly increased as well, but I get the flashing amber light and the Double NAT warning advising me to put the AE in Bridge Mode.

... and this would be "normal" as you would have two routers (with NAT enabled) in series.

The Gateway router is in the basement with great speed but it decreases as I move upstairs and to my outdoor deck where I like to work. On the deck the speed drops to 7.2 mbs, barely useable.

Again, this would be normal as Wi-Fi signals degrade over distance.

I like using the AE router, located upstairs in the kitchen and in close proximity to my deck, because I get a good signal. The internet speeds are acceptable, with the Gateway overall faster (except on the deck as noted). QUESTION: Can I keep both networks operational at the same time (checking to ignore the NAT warning on the AE) and be able to switch networks depending on location? or, should I take the Double NAT warning seriously and put the AE on Bridge Mode? Are there security concerns, connectivity or other problems that may result from keeping both routers operational?

If you want to use the AirPort Express to extend the wireless range of the gateway, it will have to be connected back to that gateway with a wired connection. Apple base stations can only extend the wireless range of another Apple base station over a wireless connection between them. Is this something that you can accommodate? That is, can you run Ethernet between the basement & the kitchen or is your home currently wired for Ethernet?

If so, then also be aware that appliances in your kitchen (microwave, stove, oven, refrigerator, etc.) can block the wireless signal so you may want to consider an alternative location for the Express.

Do you need to have two separate Wi-Fi network? If the routers can be interconnected by Ethernet, you could configure them both for a roaming type network. With this type of network, even though both routers would broadcast their own wireless network, that network would use the same network name and wireless security type & password so that wireless clients would "see" them both as a "single" network.

Finally, you want to avoid have a double NAT condition as this will definitely affect the overall network speed to/from the Internet.

so I assume it will always select the Gateway.

When wireless is involved, it is best to not assume anything.

My iPhones and MBPs are almost always on the 1st level of the house closest to the AE. I assume they are selecting the AE as the strongest signal, if in fact the AE is sending a stronger signal than the Gateway. That's what I'm trying to figure out.

Same answer. As we've mentioned previously, use AirPort Utility to find out if the iPhones and MBPs are connecting to the AirPort. They will be displayed under Wireless Clients.

You can also display Wireless Clients in a different window by opening AirPort Utility, holding down the option key on your Mac while you double-click on the picture of the AirPort. Click on the small arrow next to each client to see more details about that specific connection.

Most likely, you got "tagged" with "Wireless" because you either posted or answered a post in the Apple Networking area of the Apple Support Communities. Apple started this not too long ago to encourage active participation in the forums.

For those of us you have been here a while, see them as forum areas that you have participated in and not a measure of your knowledge level for any particular topic. As you can tell from mine, I only have a single bar so that would make me a "level 1" in this area. Trust me, it's even a bit confusing for those of us who have been here awhile.

Ref: Have fun. You deserve it. - ASC

p.s. I you want to change your current speciality, you will need to participate in one of the other areas of the ASC

Are those bars a reliable measure of how strong the signal is on the deck? Or is the download speed a better measure? Or are they essentially the same?

The "bars," similar to those you would find on most wireless clients, represent the signal strength as it is perceived by the client. However, it does NOT show the actual signal quality.

You could use a "download speed" measurement app, but this is not really telling you anything about the signal quality either. Just the end-to-end data throughput rate.

In theory, higher signal strength, would offer higher data throughput ... but this is not always the case in practice.

Think of the analogy of attending a music concert. The band is playing very loudly (signal strength), but the people around you are chatting up a storm (signal noise). Even though the music is loud, you can't make out the lyrics because of those around you.

Signal quality = signal strength - signal noise. This is called the Signal-to-Noise Ratio (SNR). The higher the ratio between the two, the better the signal quality or data throughput.

I wrote a user tip that you may find helpful. The tip was written to cover how to best place an extending base station when the connection between AirPort base stations would be wireless, but the SNR part would still be applicable for your situation. This is where your MBP will come in handy.

The goal is to have a SNR value of 30+ dB where you want the MBP to be for Internet access. If you cannot achieve this value, even if the MBP is right next to the AE, then it would indicate that the AE is faulty and your suggestion to replace it would be a good one.

How would I configure the two routers for a "roaming type network?"

I think that Tesserax will confirm that a "roaming network" is one in which all the access points use the same wireless network name and password.

So, if you want to set up the AirPort in a roaming configuration with the Comcast gateway, you would......

• Rename the wireless network that the AirPort is creating to exactly match the name of the Comcast wireless network
• Change the wireless network password on the AirPort to exactly match the password of the Comcast wireless.
• Check again to make sure that the AirPort is set up to operate in Bridge Mode.....which Apple calls "Off (Bridge Mode)".

So now, you have two "access points"......the Comcast gateway and the AirPort.....both providing the same wireless signal. The theory with a roaming network is that your wireless devices will connect to the wireless access point with the best signal quality, based on their location in relation to each access point. But unfortunately, things in the real world do not always work as well as the theory might suggest.

In general, Macs will usually do a nice job of automatically "switching" from one access point to another as they move about the house.....but iOS devices like the iPhone and iPad, other mobile devices and most PCs will not. You may likely find that you need to temporarily switch off the WiFi on an iPhone or iPad if you move from an area near one access point to another area close to another access point, then turn the WiFi back on. Then the device will usually pick up the signal from the stronger (and closer) wireless access point.

I'm still confused about which signal a device is using since both router networks now have the same name.

To find out which router your Mac is connected to, just do the following:

• Hold down the Option key, and then, click on the Wi-Fi icon on the OS X / macOS menu bar.
• Note the value for BSSID. This is the MAC address of the wireless router that your Mac is connected to.

Since it would be very unlikely that any of us would remember the MAC address of our stuff, you can use the AirPort Utility to find it for your AE, as follows:

• Run the AirPort Utility.
• Select the AE.
• Hold down the Option key, and then, select Edit.
• The AE may have, at least, two MAC addresses. One for Ethernet and the other for wireless. Just check to see if one of them matches what you found on the Mac. If they don't then your Mac is connected to the gateway and not the AE.

... and to which signal, it would be the one that the Mac is connected to.

or, should I take the Double NAT warning seriously and put the AE on Bridge Mode? Are there security concerns, connectivity or other problems that may result from keeping both routers operational?

With Double NAT, both your gateway and the AirPort Express are trying to act as routers. As Tesserax notes, you would want to avoid a Double NAT error on the network, since this condition can produce some unpredictable results......IP address conflicts, slower browsing, make communications over the network more difficult, just to mention a few.

True, sometimes, you can get away with a Double NAT error on a simple network, but there would be no reason to set things up with a Double NAT if it can be avoided.

When the Express acts as a DHCP and NAT router, it will rarely produce speeds higher than 40-50 Mbps on average, so if you want as much speed as possible from the Express, it needs to be set up in Bridge Mode. Then, you might expect to see 75-80 Mbps top speeds if the Express is in good operating condition.

A five year old Express may....or may not....be able to perform the same that it did a few years ago.

Each has a different name so I wondered if my MBP was switching between them to the strongest signal.

The MBP was not switching if the networks had different names. it will likely switch when both networks are using the same wireless network name and password.

Can anyone advise me how to take "Wireless" off my "specialty" identifier in my profile? Don't know how it got on there to begin with.

The forum software has a number of bugs that can affect things. I would not worry about this.