From: Jason1 (jason1@xxxxxxxxxx)
Date: Fri Apr 27 2001 - 14:15:00 GMT-3
I apologies, I didn't explain properly, I do understand the command of IP
Classless and it's usage. I just disagree with the way that it has been
explain in the book on usage of the command. They seems to be confuse over
the concept of "IP Classless" vs the command of "IP Classless" in the IOS. I
accept the explaination of the term "classless routing" but then he went on
to explain the use of the command "IP Classless" which is wrong.
1. When Classless routing protocol is enable , "IP Classless" may or may not
necessary appear in the statement ALTHOUGH it will not have a different in
behavior , especially in 12.x IOS.
2. He also failed to explain what happen the impact of IP Classless on
Classful protocol, (which is what you mentioned below), I felt that there is
something important for a reader to understand that the command of IP
Classless and it's impact of the Classful routing protocol.
Jason
----- Original Message -----
From: "Yurchenko, Michael" <michael.yurchenko@verizon.com>
To: "'Jason1'" <jason1@v-labs.net>; "CCIE_Lab Groupstudy List"
<ccielab@groupstudy.com>
Sent: Friday, April 27, 2001 2:16 AM
Subject: RE: Advance IP Routing - Terry Slattery - IP Classless
> I am not sure how to explain it, but assuming you read whatever the book
> says, i'll give you an example.
>
> no ip classless
> ip route 10.10.10.0 255.255.255.0 20.20.20.1
> ip route 0.0.0.0 0.0.0.0 20.20.20.2
>
> If ip classful is used, and you attempt to reach a subnet of a major
network
> for which (a network) a route is present in the table, even though this
> subnet may not be reachable via that destination, the router will send the
> traffic that way. So, if you
>
> ping 10.20.10.1
>
> which is a part of the network 10.0.0.0/8, the router will treat the route
> to 10.10.10.0/24 classfuly as a route to 10.0.0.0/8, and send the traffic
to
> 20.20.20.1, which will have no way to reach it. Now, if you were to enter
>
> ip classless
>
> in the config, then the router would begin to correctly recognize the
> subnets and if you were to
>
> ping 10.20.10.1
>
> then the router would realize that the network 10.0.0.0/8 is subnetted,
will
> forward the traffic to the default gateway and reach the destination.
>
> It can bite you mostly with static routes.
>
> Hope that helps.
>
> Michael Yurchenko
> CCIE# 6695, CCDP, CCNP ATM Specialist, MCSE
> Customer Support Engineer - 2
> michael.yurchenko@verizon.com
> 610-407-2154
>
>
> -----Original Message-----
> From: Jason1 [mailto:jason1@v-labs.net]
> Sent: Thursday, April 26, 2001 1:50 PM
> To: CCIE_Lab Groupstudy List
> Subject: Advance IP Routing - Terry Slattery - IP Classless
>
>
> I'm looking at pg 99 of Advance IP Routing by Terry Slattery and I felt
that
> it didn't give a good explaination (and in fact, I felt that it is wrong)
of
> the "IP Classless" command in the Cisco IOS and also when you should be
> using
> the command. Any comments from anybody ?
>
> Jason
> **Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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