Many of you will never see the issues involved with a 16bit or other subnet on a Class A (8bit reserved) local area network that I have. There are arguments and then there are facts. Facts first.
1. The lowest common denominator in a network is what dictates the network architecture. 2. The IP stack in many industrial systems has a limited scope. 3. A 16bit subnet in a Class A 8bit space is technically possible. In the first item I mention that devices attached or part of the network can create the logical limits that the network can operate on. From computers to switching equipment there are devices that will not _respect_ or pass on the data in the same form. For example in a wireless or fiber optic setup if both ends of termination are mis configured to "Auto Duplex" a race or fall back position will occur where the connection appears to operate _most_ of the time while it attempts to decide if its peer is full or half duplex. The second item continues the first with an example where in small routers and embedded devices which have limits or errors in the addressing scope. So, for example, a Allen Bradly Serial to Ethernet converter can have any addressing scheme applied to it, however it can only do the calculations for a 24bit network no mater how it is configured and this behaviour is documented in the manual. Newer versions have fixed this issue but it is a great example where manufacturing businesses keep machines in production far after their recommended life. In the third item the irony shows up. Technically it will work _most_ of the time. I have worked with companies that just happen to own (and quickly dispose of) equipment that will not allow these subnets. Remember that we are all at the mercy of the manufactures as the lowest common denominator of a standard. So something like this Standard / Manufacturer Implementation = Actual Operation Arguments "It works with most of my systems so I think your wrong" - Customer who ended up paying me a lot of money. "The sales man said it would work" - Customer who ended up paying me a lot of money. "Thats how the other consultant did it." - Customer who ended up paying me a lot of money. "Production is down because of your complaints, not because of the MPLS Ethernet setup" - Customer who ended up paying me a _ton_ of money. Look for the recurring concept....... I know that companies and organizations will continue to use addressing that _looks_ or _feels_ right. Remember that the _looks_ and _feels_ can bite you later. </rant> Thank you automatic spell check.... :P -- Andrew "lathama" Latham TuxTone Inc. http://TuxTone.com [EMAIL PROTECTED] _______________________________________________ Fwlug mailing list [email protected] http://fortwaynelug.org/mailman/listinfo/fwlug_fortwaynelug.org
