I'm fairly certain that's a question I wrote. When I'm writing
questions for the CCNA level, I always make a point of stating to
assume classfulness. In this specific case, it really doesn't make a
difference, since you are explicitly given a mask.
Vendors that continue to teach classful methods, other than as an
appendix to binary/CIDR methods, do a serious disservice to their
students and the industry. The Internet is absolutely NOT classful,
and it's a bad habit to get into to think in classful terms.
>Classful addressing doesn't mean that routers do not look at the subnet
>mask. Au contraire! Routers ALWAYS are concerned with subnet mask
>information!
>
>Classful addressing just means that a router that receives a routing update
>for a network for which it does not have a directly connected interface will
>assume the standard classful subnet mask. In the case of a router that does
>have a directly connected interface that is using a subnet mask that is
>borrowing bits from the host portion of the mask, it applies that mask to
>the advertised network information. Variable subnet masking (subnet masks
>of different lengths - /25, /26, /27 used in conjunction with the same
>network) is not supported.
>
>
> -- Leigh Anne
>
>At 05:48 PM 7/24/01, Guy Russell wrote:
>>Actually I disagree...
>>
>>Routers using Classful addresses, do not look at the subnet mask, nor do
>>they transmit the subnet mask...
Not quite. They look at the mask if it's on a local interface.
Otherwise, they do assume the "natural mask" on an incoming update
from routing protocols.
>Since the term classful was used, we would
>>obviously be talking about the routing protocol, so a broadcast would be
>>based only on the first octet to decide.
>>
>>Now a machine is not dependent on classful, it understands its own subnet
>>mask, and then the answer would be that... But the term Classful negates
>>that theory of it being a computer or other host...
>>
>>
>>
>>----- Original Message -----
>>From: Priscilla Oppenheimer
>>To:
>>Sent: Tuesday, July 24, 2001 5:28 PM
>>Subject: Re: ccna challenge question [7:13565]
>>
>>
>> > At 04:28 PM 7/24/01, Ed Moss wrote:
>> > >The key in the question is the word "classful".
>> >
>> > Classful doesn't mean it has to end on an 8-bit boundary.
>> >
>> > >This is a Class B address
>> > >with a 16 bit classful mask.
>> >
>> > It's not 16-bit. It says the mask is 255.255.254.0. That's 23 bits in
>the
>> > prefix (network) part.
>> >
>> > The answer is B. Put it in binary to understand it.....
>> >
>> > Priscilla
>> >
>> > >I would have to say the correct answer would
>> > >be 'C' 172.18.255.255.
>> > >Ed
>> > >
>> > > > Using classful assumptions, what is the directed broadcast address
>for
>> > > > 172.18.2.0 with the mask 255.255.254.0?
>> > > > a) 172.18.2.255
>> > > > b) 172.18.3.255
>> > > > c) 172.18.255.255
>> > > > d) 172.18.0.0
>> > >
>> > > > Answer
>> > > > b)
>> > ________________________
>> >
>> > Priscilla Oppenheimer
>> > http://www.priscilla.com
>________________________
>
>Priscilla Oppenheimer
>http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=13694&t=13565
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