sysctl -p /etc/sysctl.conf returns error

Try:

modprobe bridge
lsmod | grep bridge

You don't the those modules loaded into the kernel.

There are several bugreports about this on Red Hat Bugzilla, for example here, here and here.

Just remove the lines or run sysctl -e -p instead of sysctl -p.

You get the errors because you do not have the bridge kernel module loaded. Three choices:

1. Load the module if you need it
2. Comment those lines out from /etc/sysctl.conf
3. Let sysctl ignore the errors by giving it the -e flag.