>> Some people have claimed that the gateway address of a >> network isn't necessarily the zero address in that network.
It almost never is - conventions vary, but it is often the network address plus one, or the broadcast address minus one. >I'll go further: I don't think it's even legal for the gateway address to be >the zero address of the network (and I used to program the embedded software >in routers for a living :) ). I don't think the RFCs forbid the zero address being used, and "enlightened" network stacks allow it (typically routers) to achieve better utilisation of the limited IPv4 address space (for a /24 or larger, wasting one address out of 255 isn't too bad, but it is now typical to use much smaller nets - right down to /30). >> If that's true, then you *can't* calculate the network >> address from a host address and a netmask -- there isn't >> enough information. You can always calculate the network address from the IP address plus mask - the network address is simply the bits that are not masked. In the olden days, the mask was spelled out in octets (eg 255.255.255.0). But we've moved to a more compact and logical notation where the number of leading significant bits is specified (eg /24). -- Andrew McNamara, Senior Developer, Object Craft http://www.object-craft.com.au/ _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
