Re: RIP V1 VLSM

Hello,

I used to lab one scenario with RIPv1 having four interfaces. All belonging to the same classful network of 10.0.0.0/8. Two of them were having the mask /16 and the other ones were having /24.

Now the interesting part:

The update I received on /16 interface was sent only through the other /16 interface AND NOT VIA /24 INTERFACES.
The same is true for /24 interfaces. The update I received on /24 interface I didn't send out the other /24 interface.

At least subnets of 10.0.0.0/8 have not been forwarded to both /16 and /24 interfaces. I am not sure about different classful networks now.. I forgot this part, it was even years ago.

Hth

Regards,
Miro

On Feb 16, 2010, at 7:07 PM, Marko Milivojevic wrote:

> Hello,
>
> You guys are missing an important thing here... RIPv1 does not support
> VLSM, but it DOES support subnetting, as long as masks are of equal
> length... So, if you have two /24 subnets from major /8 network, they
> will be sent out. Now, the thing here is... if you use RIPv1, it
> cannot handle variable masks, because it's ... classless. Try
> configuring all interfaces on your routers with the same mask and see
> what happens.
>
> --
> Marko Milivojevic - CCIE #18427
> Senior Technical Instructor - IPexpert
>
> Mailto: markom_at_ipexpert.com
> Telephone: +1.810.326.1444
> Fax: +1.810.454.0130
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>
> On Tue, Feb 16, 2010 at 17:55, Roy Waterman <roy.waterman_at_gmail.com> wrote:
>> Actually all disregard my last post :)
>> Labbed it up exactly and saw this:
>>
>> R1#
>> RIP: sending v1 update to 255.255.255.255 via Serial0/0.12 (10.1.0.1)
>> RIP: build update entries - suppressing null update
>> R1#
>>
>> R2#
>> RIP: sending v1 update to 255.255.255.255 via Serial0/0.21 (10.1.0.2)
>> RIP: build update entries - suppressing null update
>>
>> ----------------
>>
>> If a /24 mask is used instead of the /16 between R1 & R2, it changes things:
>>
>> RIP: sending v1 update to 255.255.255.255 via Loopback0 (10.2.0.1)
>> RIP: build update entries
>> B B B B subnet 10.1.0.0 metric 1
>> B B B B subnet 10.3.0.0 metric 2
>>
>> R1#sh ip ro rip
>> B B 10.0.0.0/24 is subnetted, 5 subnets
>> R B B B 10.3.0.0 [120/1] via 10.1.0.2, 00:00:06, Serial0/0.12
>>
>>
>> Gotta love RIPv1.
>>
>>
>> Regards
>> Roy
>>
>>
>>
>> On 16 February 2010 17:46, Tony Schaffran (GS)
>> <groupstudy_at_cconlinelabs.com>wrote:
>>
>>> I am not sure. B This is not what I would expect of RIPv1.
>>>
>>> Maybe somebody with a more technical answer can chime in.
>>>
>>> As this has not been a topic of the CCIE blueprint for some time now and I
>>> have not come across this in an actual network for even longer, I just do
>>> not have any more knowledge of it.
>>>
>>> Sorry.
>>>
>>> Tony Schaffran
>>> Sr. Network Consultant
>>> CCIE #11071
>>> CCNP, CCNA, CCDA,
>>> NNCDS, NNCSS, CNE, MCSE
>>>
>>> CCOnlineLabs
>>> Your #1 choice for online Cisco rack rentals.
>>>
>>>
>>> From: Sarad [mailto:tosara_at_gmail.com]
>>> Sent: Tuesday, February 16, 2010 9:42 AM
>>> To: groupstudy_at_cconlinelabs.com
>>> Cc: Nadeem Rafi; Cisco certification
>>> Subject: Re: RIP V1 VLSM
>>>
>>> Hi tony,
>>>
>>> But as it is a contiguous network it should advertise /16 isnt it? . I
>>> initially thought it should also advertise /24 :(. I am trying to catch
>>> what
>>> happen with the debug but it doesnt show much pls share if you can capture
>>> anything on debug which shows why it is not advertising.
>>>
>>> Sara
>>> On Tue, Feb 16, 2010 at 11:05 PM, Tony Schaffran (GS)
>>> <groupstudy_at_cconlinelabs.com> wrote:
>>> Interesting. B I would not even expect the /16 to be advertised, but it is
>>> as
>>> you describe.
>>>
>>> Also as you describe, the /24 definitely does not get advertised.
>>>
>>> Tony Schaffran
>>> Sr. Network Consultant
>>> CCIE #11071
>>> CCNP, CCNA, CCDA,
>>> NNCDS, NNCSS, CNE, MCSE
>>>
>>> CCOnlineLabs
>>> Your #1 choice for online Cisco rack rentals.
>>>
>>>
>>> From: Sarad [mailto:tosara_at_gmail.com]
>>> Sent: Tuesday, February 16, 2010 9:31 AM
>>> To: groupstudy_at_cconlinelabs.com
>>> Cc: Nadeem Rafi; Cisco certification
>>>
>>> Subject: Re: RIP V1 VLSM
>>>
>>> Yes I have set it up, as per theory of RIP as it is a contiguous network
>>> (10
>>> range) it should send it. When the loopback is a /16 it sends the loopbacks
>>> but when I change it to /24 it doesnt send it. So is this a illustration of
>>> RIPV1 does not support VLSM ?
>>>
>>>
>>> On Tue, Feb 16, 2010 at 10:39 PM, Tony Schaffran (GS)
>>> <groupstudy_at_cconlinelabs.com> wrote:
>>> I do not think RIPv1 will be sending /16
>>>
>>> RIPv1 is classless and 10.x.x.x is /8
>>>
>>> Have you configured this in a lba to see for yourself?
>>>
>>> Tony Schaffran
>>> Sr. Network Consultant
>>> CCIE #11071
>>> CCNP, CCNA, CCDA,
>>> NNCDS, NNCSS, CNE, MCSE
>>>
>>> CCOnlineLabs
>>> Your #1 choice for online Cisco rack rentals.
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>>> Nadeem Rafi
>>> Sent: Tuesday, February 16, 2010 8:53 AM
>>> To: Sarad
>>> Cc: Cisco certification
>>> Subject: Re: RIP V1 VLSM
>>>
>>> you will not be able to see /24 as rip v1 will be sending /16 major network
>>> only.
>>>
>>> HTH
>>>
>>> On Tue, Feb 16, 2010 at 7:39 PM, Sarad <tosara_at_gmail.com> wrote:
>>>
>>>> Hi Expert,
>>>>
>>>> If I have the following scenario, that is two routers connected back to
>>>> back
>>>> with a 10 range /16 ip & there are two loopbacks configured on each
>>> router
>>>> with the same class IPs. If I run RIPV1 on this. Will it advertise my
>>>> loopbacks to each other.
>>>>
>>>> B B B R1
>>>> R2
>>>> S0 - 10.1.0.1/16 <---------------------------> S0 -10.1.0.2/16
>>>> L0 - 10.2.0.1/24 B B B B B B B B B B B B B B B B B B B B L0 -
>>> 10.3.0.1/24
>>>>
>>>> Regards
>>>> Sara
>>>>
>>>>
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>>>
>>
>>
>> --
>> Regards
>> Roy
>>
>>
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Received on Tue Feb 16 2010 - 19:17:43 ART