This is the minimum size an IPv6 implementation must support. This makes it the default for IPv4 too, which presumably is also generally routable (otherwise, setting this to 0 falls back to the minimum of 576 for IPv4).
This is the minimum size an IPv6 implementation must support. This makes it the default for IPv4 too, which presumably is also generally routable (otherwise, setting this to 0 falls back to the minimum of 576 for IPv4).