Mapping a MAC to an IP...

Peter Laws plaws at
Wed Jan 21 16:16:34 UTC 2009

Simon Hobson wrote:

> Yes, you MUST split a range as you have shown. 

 > But, you should also
> NOT put your host statements inside a subnet declaration.

Yeah, I've seen the messages in syslog and wondered.

> Host declarations are global in scope, and so are valid even if a 
> client is connected to a different subnet (in which case it will get 
> a dynamic address from that subnet rather than the fixed address). 
> But what would happen is that the client would get a suitable IP 
> address, but inherit options (such as routers) from the subnet where 
> the host statement is declared - I think you can imagine the 
> confusion that causes !

That makes no sense ...  if a particular host connects to a different 
subnet, I'd want it to get the information *appropriate for that subnet*, 
not the one where it may have a static IP/reservation/whatever you want to 
call it.   What am I missing?

I'm with Mr Snyder - it's kind of a pain.  I'm only dealing with a /23 and 
a dozen or so reservations, but still.

Peter Laws / N5UWY
National Weather Center / Network Operations Center
University of Oklahoma Information Technology
plaws at
Feedback? Contact my director, Craig Cochell, craigc at Thank you!

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