Slow Airport Extreme on LAN and WIFI

I thought AirPort Extreme 802.11n (4th Generation) was supposed to give me up to one gig over LAN or WAN. 

I wanted to start with this one to help you set some expectations for your 4th gen AirPort Extreme base station. It also is important to note what these Gigabit speeds mean. When operating in bridge mode, that is with the base station not performing as a router, you potentially can get near Gigabit speeds on any of its Ethernet ports. Those speeds drop to half that when it is performing as a router, which in your case it is. This is the speed measured through the WAN-LAN interface with DHCP and NAT enabled. I suggest that you pay a visit to the SmallNetBuilder website where they test numerous routers, including some of the Apple models to get a better idea on what you can expect for both wired and wireless performance.

Computer hooked up directly to AE router LAN– about 90 MB

You are using "MB" for performance. Are you referring to MBps (Bytes per second) or Mbps (bits per second)? The latter is what is typically used for this measurement. Going with Mbps, when connected directly by Ethernet, your Mac should be getting between 400-500 Mbps. Far greater than what your ISP is providing you. These measurements are normally made between a test device connected to the WAN side of the base station and a device directly connected to the LAN side. Traffic from the Internet is not involved here. In theory, if your ISP provided you with 400-500 Mbps download service, you should get close to this at your Mac when connected directly to the base station by Ethernet.

Since yours is not even getting anything near what your ISP is providing is indicating (to me) that there is something amiss between the router and your Mac since you were getting "full" speed when the Mac was directly connected to the modem.

What could be the potential cause? A number of things could be possible:

1. A faulty Ethernet cable. Guessing that you used the same Ethernet cable to test your Mac connected to the modem and the base station, this is most likely not the cause.
2. A faulty Ethernet port on your Mac. For this one I would suggest that you run Apple Diagnostics to see if there are any hardware issues with your Mac.
3. The Ethernet port on your Mac is mis-configured. You can verify what the current configuration is by going to: System Preferences > Network > Ethernet > Hardware tab. By default, Configure = Automatically. This may not be the best setting for your Mac. I suggest that you change that setting to: Manually, and then, try other settings to see which provides the best results.

As you are probably already aware, the "best" value for MTU is just before packets get fragmented.

One way to test this is by using the ping command in the Terminal app, as follows:

• The default MTU value should be 1500 (or 1492 if the connection is via PPPoE. )You can verify this value by entering the following in Terminal: networksetup -getMTU en0 <enter>
• ping -D -s 1472 www.apple.com <enter> If you get either a "Message too long" or "packet needs to be fragmented" error message in ping result, reduce 1472 by 10 until you no longer get the error message. Then add 28 to this value (since the ping packet size, not including IP/ICMP header is 28 bytes), to arrive at the MaxMTU size.

I just want to affirm virtually everything that was said so far in the two great responses above mine.

That being said, it does seem like the Ethernet port on your Mac itself is fine since it gets 300+ MB hooked directly to the modem. All of the poor Wi-Fi is easy to ascribe to whatever interference, or a worn out Wi-Fi in the AE. Most consumer Wi-Fi devices start to get worn out in about 18-36 months with degraded performance. So I'm not even going to go there because what concerns me the most is that you get 90 MB even when hooked up directly to the AE via Ethernet, the same as in Wi-Fi.

You should be getting close to what you get hooked up to the AE via Ethernet as what you get hooked directly into your modem. To me that tells me there's an issue with the AE. Is it in fact many years old as we're all assuming? Wi-Fi transmitters/receives get worn out just like tires on a car, but the Ethernet should not be. This makes me think your AE is in fact pooping out across the board (and not just its Wi-Fi) or there are some non-ideal settings going on elsewhere.

I would try resetting your AE and making sure it's not showing that there's a new firmware update available as one was released not too long ago (for the first time in 4 years or so!).

Being two feet away between your MacBook Pro and the router (or AE) is not a good thing. Being 3-6 feet away is better.

If you open the network preferences on your Mac click on Ethernet in the list of interfaces, click the Advanced button and the Hardware tab. Change "Configure" to Manually and you can set the different speed/settings here *as already pointed out* but specifically I am focused on the MTU. You can change "MTU" to Custom and try both the lowest size (1280) and the highest size (9000) and see what those numbers do for your performance.

Note: I'm 98% sure these changes take effect immediately and don't require a restart.

Here is screenshot from iphone of the TC I setup to show you how to get the WAN link speed.

Open the airport utility on the iPhone/ipad.

Type in your password so you can access the details.

On the first screen then you can see the connection where it shows excellent on mine.. tap the arrow.

On this screen it will show you the actual WAN link speed.

This is the only place Apple provided to get that info. There are other sneaky ways to find it.

I suspect your Modem to WAN connection is running 100Mbps.

The LAN side to your computer.. is easy to find.. as per rcosta887 screenshot.

I don't think you should have a big problem there.

(Changing MTU I doubt will do anything though).

There is no way to fix WAN to modem issue if that is what it turns out to be.

I have run into ethernet issues on the older airport and Time Capsule.. which was caused by poor capacitors on the 1.8v line.. This is Time Capsule A1355 model which is very similar to A1354 which is your Gen4 AE. I don't know if the same problem happens.. It is an issue on very few of the A1355 and early A1409.

See https://sites.google.com/site/lapastenague/a-deconstruction-of-routers-and-modems/apple-time-capsule-repair/new-issue-with-a1355-gen-3-tc

90Mbps is what you are getting.. We try and use B for Bytes and b for bits..

Network speeds are in bits.. actual file transfers are in Bytes.. just to make it confusing Apple now uses digital Bytes not binary Bytes..

Whenever we see 90Mbps we know your issue is ethernet is failing to connect at gigabit.. which it should.. and has dropped back to 100mbit..

This can happen either between your Mac and Extreme or between the modem and the Extreme.. I suspect the later.. because Arris SB6183 SURFboard DOCSIS 3.0 Cable Modem can be a nasty unit with Apple.. and I suspect the WAN port has dropped back to fast ethernet.

You can check in the airport utility in iphone or iPad.. I don't have anything setup at the moment to show you but that is where I suspect problems can exist.

A Gen4 Extreme.. is it worth messing with.. because I suspect the issue can also just be age.. it is time to move on bro.

You need a new router as in about 6 years ago.. now is the time.. for the 6 year overhang to collapse and you invest some cash in new router.

Yes that would have been helpful. We have found that the Motorola/Arris SB61XX series of modems to be problematic with the Apple routers. Neither are necessarily bad in themselves, but they just don't "play nice" together. In this case, it looks like the Arris was faulty, so that would yet to be proven here.

Anyway, I'm glad you got it worked out.