Wireless goes to a crawl after connecting switch

[animematt]

So I am a little confused by this. I have a Asus rt-n56u and I just plugged in a cisco 4 port switch to it so I am setup as ISP>Router>Switch. Now the odd thing is when I plug in the switch my wifi goes to a crawl to the point that nothing can browse with it. This asus router is a duel-band and if I connect to the 5Mhz it work just fine however when I go with the 2.5 the wifi basically stops working. I don't really want to use the 5Mhz because the range is bad and can't go everywhere in my house where my wireless devices are. I this a QoS issue or is the 2.5 band just full and can't support any more bandwidth on it? Would love some feedback on this!

 

[nigelivey]

DL Inssider and have a look, there is a free version. This will give you some indication of congestion on the 2.4 a 5 Ghz bands. With this information you may be able to improve things by changing channel. This shouldn't be altered by plugging in a wired switch however so there may be other issues. What model of switch is it please.

 

[animematt]

It is a Cisco Linksys EZXS55W Switch.

 

[nigelivey]

And you are using the uplink port but not the one to the right of it? (They are wired together, use the uplink port back to the router and leave the one to the right empty)