After upgrade to 600Mbps, actual speed is 50Mbps

[Seshar]

I recently upgraded from a 300Mbps plan to a 600Mbps plan and now my speed is terrible. On the 300Mbps plan I was getting really close to 300Mbps and now I am getting 50-80Mbps. I have tried rebooting the gateway. I am using new Xfinity equipment that was shipped when I upgraded. What can I do next?

[esligia54]

I am having the same exact issue! I have an SB6190 Modem (less than 3 months old) and also I have a brand new Linksys EA7200 router.  

I disconnected all of my splitters and coaxial from the amplifier today.  I now have 75mbps instead of 50mbps.  I got on with a chat agent and he checked everything and sent me to advanced technical support.  I am waiting for the phone call now.

Let's see what happens.

Do you have the same setup? 

[NikBee]

basically the same for us...upgraded to the 600Mbps from 175.  So, I got a new SB6190 because my old surfboard could only handle my previous speed. 

But, now the top download speed I can get is 90-100.  Before switching out my old router this morning, I was getting 135.

So...not real sure what is going on.  The tech didn't either.   yay.