What we’re doing here is creating a new network location which is going to have a configuration different from the defaults. First, we’ll use a completely new network setup. Then, we’ll set DNS on the computer rather than waiting for OS X to get DNS details from the wi-fi router, which alone can resolve many issues with DNS lookups, since Yosemite seems to be finicky with some routers. Finally, we’re going to set a custom MTU size that is slightly smaller than the default, which will get rejected less often by a router, it’s an old netadmin trick that has long been used to fix network troubles.