As we have seen in “Use local mirror to build yocto filesystem from internal server” if you have setup the yocto to download from local mirrors and now it seems everything is fine and you no longer need to download external source code, we can setup yocto to make sure it is really not reaching external network to download from instead, and verify that we have all source code necessary to compile yocto filesystem locally.
For this, we need to add following line into build/conf/local.conf
$ vim build/conf/local.conf
BB_NO_NETWORK = "1"
This will block all network access and if we do fresh build, we will see if yocto attempted to download from internet and failed, if failed we can adjust failed recipes SRC_URI to download from local mirror.