Re: VLSM and IP Addressing

From: Ben Rife (brife@xxxxxxxxxx)
Date: Mon Jan 31 2000 - 12:14:19 GMT-3


   
Thanks for calming my fears guys !!!
You are the best,
Ben

----- Original Message -----
From: <simon.baxter@citicorp.com>
To: <brife@bignet.net>; <ccielab@groupstudy.com>; <gahm@gci.net>
Sent: Monday, January 31, 2000 6:17 AM
Subject: RE: VLSM and IP Addressing

This is a horrible Cisco gotcha. There's a few guys in my office which
are studying for their CCNAs etc and came to me with this question.

Their training books, based on the Cisco exams etc, imply that unless a
specific class is stated - assume an 8 bit (class A) base on any bit
mask given.

ie there was a question of "how many nets/hosts on a 22 bit subnet
mask". What this translated to was actually how many nets/hosts on a 30
bit mask (22+8).

But since your question included a class indication, you use that as
your base.

ugly huh! ugly but true.

   -----Original Message-----
   From: gahm [mailto:gahm@gci.net]
   Sent: Monday, January 31, 2000 6:17 AM
   To: brife; ccielab
   Cc: gahm
   Subject: Re: VLSM and IP Addressing

   Ben,
   What they mean is to add 8 subnet bits to the natural mask. In other
   words, since 130.10.X.X is a class B address, which has a natural
   mask of 255.255.0.0, they are indeed asking you to
   use a 24 bit mask.

   Dave

          -----Original Message-----
          From: Ben Rife <brife@bignet.net>
          To: ccielab@groupstudy.com <ccielab@groupstudy.com>
          Date: Sunday, January 30, 2000 9:08 PM
          Subject: VLSM and IP Addressing

          I have a practice lab here that has the following addressing
   requirement.

          Configure all of the networks using network 130.10.X.X.
          Use an 8-bit subnet mask unless otherwise specified.

          This troubles me. Correct me if I'm wrong, but wouldn't this
   be a problem for routing? I mean if you have the following senario:

          |--R1------R2--|

          R1's E0 is 130.1.1.1 255.0.0.0
          R2's E0 is 130.2.2.2 255.0.0.0

          Try getting any protocol to run on this network...it won't
   work will it?
          Essentially these two addresses are on the same network. Do
   you agree? This
          has me puzzled. This is the 2nd time I've seen this IP
   addressing senario in
          a practice lab today. I wouldn't know what to do if I was
   asked that on the
          lab.

          OR...OR....does it mean to use a /24 mask eventhough it calls
   for an 8-bit subnet mask?

          Thanks for the help,

          Ben



This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 08:22:46 GMT-3