Just got Internet 300, and pretty much all of my devices get the correct speed except my Macbook Pro laptop. All speed tests usually result in about half of the speed I should be getting. Need help troubleshooting!
When I go into the Network Utility and check the Link speed, it says 450Mbps, and the network adapter supports 802.11 a/b/g/n - so I know it should be fine with Internet 300.
The laptop is only really between 36-48 inches from where the modem is located.
That link speed is not fast enough. I think you misunderstand link speed - a good portion of link is used for signaling, around 50%, and it is half duplex, so you can only count on getting approximately 1/3 the link speed for throughput. 450 Mbps link speed would give you an actual maximum rate of around 150Mbps. (450 Mbps / 3 = 150Mbps)
You will need ~900 Mbps link speed to get 300Mbps actual speed. To get close to this link speed (866 Mbps is a more normal value) you need at least 2 chain AC wireless with 256QAM modulation on an 80 MHz channel size (wireless A is not sufficient):
If your MacBook does support wireless AC, a link speed of 450Mbps according to the chart only happens with 3 chains with a 40MHz channel size and 64-QAM, so if this is the case, your modulation is not high enough and channel size is too small.
If your MacBook does not support wireless AC, 450Mbps is the highest data rate (another word for link speed) that it could get with 5GHz wireless N on 3 chains. Unfortunately from your description this seems most likely (since your wireless did not mention ac support, only a/b/g/n), and you will be limited to 150Mbps actual Internet speed on the MacBook unless you buy an external dual or triple chain wireless AC dongle that can be plugged in by USB or connect with a cable instead of wireless. You seem to be currently at the maximum limit of the wireless that is in the MacBook.
That would explain everything. Since it was the only device not getting the 300Mbps download speed, I knew it was something to do with the laptop, but hoped it was just a simple setting I was overlooking.
The network adapter on my MBP does not appear to support wireless AC. I don't think it's particularly worth going out to buy a wireless AC dongle unless it's dirt cheap.