John upgraded his internet but his laptop says it only has 2.4 GHz available. Leo says that means his router is only 2.4 GHz. 802.11N routers are dual band with 2.4 and 5 Ghz bands. And there's even tri-band routers that offer two 5 GHz channels along with a 2.4 GHz channel. His laptop may also just be able to connect to 2.4 Ghz. John should look in his BIOS and software to see if the 5.0 GHz band is turned off.
Al is having trouble with his Chromecast dropping his internet connection. Leo says that Al is using Comcast's ActionTek router and there may be interference on the 2.4 Ghz band. He recommends going with a higher band, like 5 Ghz. Most other stuff uses 2.4 Ghz and it's getting pretty crowded. Another option, if he can't go with 5 GHz, is to choose another channel on the farthest end. ActionTek uses Channel 1, so he should try Channel 11. That should clear the field and help Al to connect.