I don't think its unreachable. Cisco tests OTOH.... Most people use the 2^n-2 rule for determining the number of available/usable networks. The -2 is there because of the need to remove the network and broadcast subnet. I don't write the rules, I just question them :)
I agree with you 100% that there are 16 subnets. I was trying to point out that those that we bringing up the fact that in the "old world" only 14 were available were not reading the question correctly. It didn't ask for usability, it asked for quantity. As I am sure you are aware, as you take more and more Cisco tests, it becomes important to clarify what they are actually asking for, not what would make sense for them to ask for... Its also important to note that IP subnet zero is still needed on Cisco eq for it to route/subnet properly, they just enabled it by default now... Thanks Larry -----Original Message----- From: Chuck [mailto:[EMAIL PROTECTED]] Sent: Friday, July 12, 2002 3:13 PM To: [EMAIL PROTECTED] Subject: Re: Class C summarization question [7:48367] ah, but that is old world classful thinking. as per RFC 1812, effectively there is no such thing as subnet zero any longer. per that RFC, all routers SHOULD route to any address in the form of network:host, or network:subnet:host. subnet zero is a holdover from the old world. it is there because of the concern that there is still so much old world equipment out there. RFC 1812 is dated June 1995, and one wonders how long it takes in practical terms for all manufacturers and all software stack writers to get all their stuff up to standard.. not to mention how long it takes for the old stuff to be removed from production. hhhmmmmm..... a brief look through ARIN seems to indicate that assignments are not made out of "subnet zero" space but that is still a different question. a summarization produces a single route where several existed before. if you see a summary 192.1.0.0/16, why would you think that 192.1.0.0/24 is unreachable? Chuck ""Roberts, Larry"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Just to jump in late on this, but... The question doesn't ask how many > of those class "C" are usable, which would be dependant on subnet O, > but instead the question was how many you would be able to summarize. > A /20 would in fact summarize 16, 14 of which are useable without > subnet zero... > > > Thanks > > Larry > > > -----Original Message----- > From: Dain Deutschman [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, July 10, 2002 4:05 PM > To: [EMAIL PROTECTED] > Subject: Re: Class C summarization question [7:48367] > > > Hey everyone, > > Thanks for all of your help. I have decided that 16 must be correct > since it > makes perfect sense and most of you back that up as well. I think the > test question was just plain wrong. Anyway...I passed the CCNP Routing > exam today > so I'm pretty happy. : ) Groupstudy is a great learning resource. > Thanks everyone. Dain. > > ""Dain Deutschman"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > I'm confused about a practice question for BSCN that I came across: > > > > Your routing tables are getting very large and you need to configure > > route summarization. How many class C internet addresses can you > > summarize with > a > > /20 CIDR block? > > > > Answer: 8 > > > > Would it not be 16? Where am I going wrong? > > > > -- > > Dain Deutschman > > CNA, MCP, CCNA > > Data Communications Manager > > New Star Sales and Service, Inc. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=48734&t=48367 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
