From: Nadeem Ansari (nadeem.ansari574@gmail.com)
Date: Fri Mar 20 2009 - 08:15:11 ART
RIGHT...
ip class-less command is to change the router's route lookup method,
In "no ip class-less" configuration router will do a classful route lookup
looking for major network of a perticular destination and ignoring the
default route(0.0.0.0).
In "ip class-less" configuration router will do bit-by-bit matching in
routing table for destination and if not found any specific route it will
choose any default route configured.
Regards
Nadeem
On Fri, Mar 20, 2009 at 3:26 PM, libone mhlanga <libone@lycos.com> wrote:
> I think these are good questions ...I will ans the 1st part according to
> my understanding and research the rest ...Doyle " Routing TCP/IP" Volume
> I has a section on classful behaviour :-
>
> "The way I understand it, is without the ip classless command, a router
> would check the routing table for a known major class of the destination,
> if no subnets are found within that major class, the packet is dropped.
> However if the packet is for a destination, totally unknown to the
> router,
> it will use the default route?"
>
> I would say no without the ip classless cmd the router will never use its
> default route !
>
> <---------[ Received Mail Content ]----------
>
> Subject : Classful Vs. classless behavior [7:134774]
>
> Date : Fri, 20 Mar 2009 05:06:36 -0400
>
> From : "k.jungle@gmail.com" <k.jungle@gmail.com>
>
> To : cisco@groupstudy.com
>
> Hi All,
>
> My first post here, so I hope im being specific enough :)
>
> I am studying some classles versus classful behavior, and a couple of
>
> things came up.
>
> First of, the "ip classless" command seems to only affect the routing
>
> process, and has nothing to do with the routing protocol in place, is
> that
>
> correct?
>
> The way I understand it, is without the ip classless command, a router
>
> would check the routing table for a known major class of the destination,
>
> if no subnets are found within that major class, the packet is dropped.
>
> However if the packet is for a destination, totally unknown to the
> router,
>
> it will use the default route?
>
> With the ip classless command however, you could have a major network
>
> matching the packets destination address, but if no more specific route
> is
>
> known, it would still use the default route?
>
> The final thing that wont quite stick, is with a classful routing
> protocol
>
> (RIPv1 for instance), if it receives a route update, with a major network
>
> different from the receiving interface, it will assume its classful, and
>
> use the classful "part" of that route.. For example. 172.16.2.0 is
> received
>
> on an interface 10.10.10.1. It will install the route 172.16.0.0 into the
>
> routing table? And the VERY final (i promise :) ) is if it receives a
>
> subnet of a major net, on an interface with the same major net, it will
> use
>
> the interface's mask to install into the routing table. For example.
>
> 192.168.2.16 is received on an interface with an ip of 192.168.2.1/28, it
>
> will install that route as 192.168.2.16/28 as well?
>
> Sorry if its confusing, and please let me know if i can elaborate in any
>
> way!
>
> Thanks in advance!
>
>
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