IP Subnet-Zero

I thought it would be interesting to take a little stroll through history and look at something that really isn't relevant to today's network, but was something that you weren't allowed to use in days gone by.  As the blog title says, that something is IP Subnet-Zero.

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What is IP Subnet Zero?  Well, it's a legacy command on Cisco routers the controls whether or not the use of the all zeros subnet is permitted.  What's the all zeros subnet?  To properly understand what the all zeros subnet is we need to first remember what classful networking was, and how things all got started in IP beginning with RFC 791. 

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How IOS Cheats When Using the Network Command

When you type a command into the IOS CLI you normally expect IOS to execute your instruction as typed.  You don't expect IOS to modify what you typed, or to assume you meant something other than what you actually typed in.  In fact, to me that behavior is extremely undesirable.  I understand there are some assumed defaults where if you omit certain keywords then IOS imposes on for you.  That's fine.  But sometimes IOS changes what you typed in to something completely different.  The network command contains one such example.

IP Directed Broadcast

I have this stupid blog, so I might as well put something on it.  And as you can tell from the other posts on this blog, I post on Networking-Forum.com.  The other day I broke down what an IP directed broadcast is.  You can read the full thread here, but here's the big post that had the most detail after the jump.