Netmask issue

Jeff Wieland wieland at
Fri Oct 9 11:23:35 UTC 2009

Ray Phillips wrote:
>> What I do is to *never* use an "option subnet-mask" statement, and 
>> just let the subnet statement handle it, *unless* you have a subnet 
>> that needs a different mask, and then (and only then) I assign it with 
>> "option subnet-mask".
> What's an example of a situation where a client would need to be given a 
> subnet mask different from the one specified on the subnet line?
> I wonder if the broadcast-address option has to be supplied, since it 
> can be inferred from the subnet and netmask values?
> Ray

I've seen setting the netmask to a different value done to attempt
to limit the broadcast traffic for devices that were behind a NAT
device, and that only needed to communicate with that NAT device.
I don't know how successful that was.
           Jeff Wieland            |         Purdue University
    Network Systems Administrator  |        ITN&S Data Networks
        Voice: (765)496-8234       |        501 Harrison Street
         FAX: (765)494-6620        |   West Lafayette, IN 47907-2025

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