Re: Rip Networks

Careful Aashish!

It sounds like you might be confusing EIGRP with RIP version 2. With
RIP v2 all we can specify is a classful network prefix - no mask. The
IOS will actually let you type in the exact subnet address, but when
you look at the running-config, you will see the classful
representation.

Also, remember the network command when used with IGPs is not really
indicated what prefix that is advertised. This is more the behavior of
the network command with BGP. It is my belief that Cisco is moving
away from the use of the network command with IGPs as a result of this
confusion.

With RIP version 2 we would indeed need to filter the 10.10.12.0/24
prefix if we did not want it advertised to R3 in the example below.

Warmest Regards,

Anthony J. Sequeira, CCIE #15626
http://www.INE.com

Test your Core Knowledge today!
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On Oct 2, 2009, at 6:13 AM, aashish kapoor wrote:

> Hi Rob,
>
> I think if you use
> no auto-summary
> command and then advertise the specific network with mask you will
> not get
> magicall connectivity.
>
> correct me if I am wrong
>
> Regards
> Aashish Kapoor
> Training is to make as many mistake as much possible so that once
> done you
> know all the wrong ways...
>
> On Fri, Sep 25, 2009 at 3:12 AM, Rob Phillips
> <rrphillips_at_swankav.com>wrote:
>
>> I have been wondering if I am reading to much into questions or not
>> enough
>> when it come to RIP. See the example below and if something like it
>> happened
>> to show up on a lab how would you handle it?
>>
>> R1 --- 10.10.12.0/24 ---- R2 ---- 10.10.23.0/24 ---- R3
>> |
>> |
>> Loopback 1
>> 10.10.2.2/32
>>
>>
>> Questiomn asks you to Enable rip on R2 and R3. Put the link
>> between R2 and
>> R3
>> as well as R2's loopback into RIP.
>>
>> So you do the following on R2
>>
>> router rip
>> ver 2
>> no auto
>> network 10.0.0.0
>> default pass
>> no pass int f0/1 - Interface between R2 and R3
>>
>>
>> Now after you configure R3 you will see the 10.10.12.0/24 network
>> from R3.
>> In
>> this way R3 has "magically connectivity" to the 10.10.12.0 network
>> via
>> RIP.
>>
>> Now I could filter that network out of the updates such as an
>> offset list
>> of
>> 16 directed on the outbound updates to R3 to make it disappear.
>> So, would
>> any
>> of you go through that step to filter out the additional network?
>>
>> I can see it looked at in grading to be a toss up. Would that be a
>> good
>> question to ask the Proctor. Something like "I understand that Rip's
>> network
>> command is classful based, so by adding the Network 10.0.0.0
>> command will
>> pull
>> all of the 10.x.x.x networks into Rip. Is this acceptable or
>> should I
>> filter
>> the network(s) no listed in the question from being broadcasted to
>> other
>> RIP
>> routers"
>>
>> Rob
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
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>
>
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>
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Received on Fri Oct 02 2009 - 09:50:34 ART