From: Divin Mathew John (divinjohn@gmail.com)
Date: Sun Mar 29 2009 - 19:14:46 ART
HTH ! anytime! keep the questions flying...! i am also studying for CCIE R
&S!!
Thanking You
Yours Sincerely
Divin Mathew John
divinjohn@gmail.com
divin@dide3d.com
+91 9945430983
+91 9846697191
+974 5008916
PGP PUBLIC KEY BLOCK @ http://www.dide3d.com/divin_Public_PGP_key.txt
Sent from: Bangalore KA India.
On Mon, Mar 30, 2009 at 3:44 AM, Raghav Bhargava <raghavbhargava12@gmail.com
> wrote:
> yup thanks guys..will do it
>
> thanks all
>
> raghav
>
>
> On Sun, Mar 29, 2009 at 3:12 PM, Divin Mathew John <divinjohn@gmail.com>wrote:
>
>> yeah lab it up.... read up on the 2 URLs i send you.! Hope that makes it
>> easy.!
>> Thanking You
>>
>> Yours Sincerely
>>
>> Divin Mathew John
>> divinjohn@gmail.com
>> divin@dide3d.com
>> +91 9945430983
>> +91 9846697191
>> +974 5008916
>> PGP PUBLIC KEY BLOCK @ http://www.dide3d.com/divin_Public_PGP_key.txt
>> Sent from: Bangalore KA India.
>>
>> On Mon, Mar 30, 2009 at 3:41 AM, Salah ElShekeil <
>> salah.elshekeil@gmail.com> wrote:
>>
>>> you have to lab it up Raghav you will understand,
>>>
>>> if you have questions just ping :)
>>>
>>>
>>>
>>>
>>> On Mon, Mar 30, 2009 at 1:09 AM, Divin Mathew John <divinjohn@gmail.com>wrote:
>>>
>>>> yeah. salah just put it Small and Simple!
>>>> Thanking You
>>>>
>>>> Yours Sincerely
>>>>
>>>> Divin Mathew John
>>>> divinjohn@gmail.com
>>>> divin@dide3d.com
>>>> +91 9945430983
>>>> +91 9846697191
>>>> +974 5008916
>>>> PGP PUBLIC KEY BLOCK @ http://www.dide3d.com/divin_Public_PGP_key.txt
>>>> Sent from: Bangalore KA India.
>>>>
>>>> On Mon, Mar 30, 2009 at 3:37 AM, Salah ElShekeil <
>>>> salah.elshekeil@gmail.com> wrote:
>>>>
>>>>> if the router who is generating the summary have no longer match in its
>>>>> routing domain then it will discard it
>>>>>
>>>>>
>>>>> On Mon, Mar 30, 2009 at 1:03 AM, Raghav Bhargava <
>>>>> raghavbhargava12@gmail.com> wrote:
>>>>>
>>>>>> Hi divin/salah,
>>>>>>
>>>>>> Can you guys please answer my questions that I requested for in my
>>>>>> mail..I understand in EIGRP wen we create a summary address it creates a
>>>>>> Null 0 route but my question is if a packet comes in for a different network
>>>>>> what happens then..
>>>>>>
>>>>>> raghav
>>>>>>
>>>>>>
>>>>>> On Sun, Mar 29, 2009 at 3:00 PM, Salah ElShekeil <
>>>>>> salah.elshekeil@gmail.com> wrote:
>>>>>>
>>>>>>> yep in rip it won't creat route to Null you have to do it manually
>>>>>>>
>>>>>>> ip route xxxx xxxx null0
>>>>>>>
>>>>>>> On Mon, Mar 30, 2009 at 12:56 AM, Divin Mathew John <
>>>>>>> divinjohn@gmail.com> wrote:
>>>>>>>
>>>>>>>> and i do think its only in OSPF and EIGRP when u do summarize routes
>>>>>>>> internal or external that creates a NULL route automatically.! for
>>>>>>>> rip i
>>>>>>>> guess will have to create a static route pointing to the Null0 with
>>>>>>>> a higher
>>>>>>>> administrative distance than any other routing protocol....to avoid
>>>>>>>> loops/!
>>>>>>>> Thanking You
>>>>>>>>
>>>>>>>> Yours Sincerely
>>>>>>>>
>>>>>>>> Divin Mathew John
>>>>>>>> divinjohn@gmail.com
>>>>>>>> divin@dide3d.com
>>>>>>>> +91 9945430983
>>>>>>>> +91 9846697191
>>>>>>>> +974 5008916
>>>>>>>> PGP PUBLIC KEY BLOCK @
>>>>>>>> http://www.dide3d.com/divin_Public_PGP_key.txt
>>>>>>>> Sent from: Bangalore KA India.
>>>>>>>>
>>>>>>>> On Mon, Mar 30, 2009 at 3:25 AM, Divin Mathew John <
>>>>>>>> divinjohn@gmail.com>wrote:
>>>>>>>>
>>>>>>>> > The Null interface is typically used for preventing routing loops.
>>>>>>>> Enhanced
>>>>>>>> >> Interior Gateway Routing Protocol (EIGRP), for instance, always
>>>>>>>> creates a
>>>>>>>> >> route to the Null0 interface when it summarizes a group of
>>>>>>>> routes. Whenever
>>>>>>>> >> a routing protocol summarizes, this means that the router might
>>>>>>>> receive
>>>>>>>> >> traffic for any IP address within that summary. Because not all
>>>>>>>> IP addresses
>>>>>>>> >> are always in use, there is a risk of looping packets in case
>>>>>>>> default routes
>>>>>>>> >> are used on the router which receives the traffic for the
>>>>>>>> summary.
>>>>>>>> >
>>>>>>>> >
>>>>>>>> >
>>>>>>>> http://www.cisco.com/en/US/tech/tk364/technologies_tech_note09186a00801c9a6e.shtml
>>>>>>>> > refer that doc. u will know why null0 is created
>>>>>>>> > and
>>>>>>>> >
>>>>>>>> >
>>>>>>>> http://www.cisco.com/en/US/tech/tk364/technologies_tech_note09186a00801c9a6e.shtml
>>>>>>>> >
>>>>>>>> > However, in IOS levels 12.1(6) and higher, this discard route is
>>>>>>>> generated
>>>>>>>> > by default, and you don't need to create it. If you want to
>>>>>>>> disable creation
>>>>>>>> > of the discard route, use the *no discard-route* command:
>>>>>>>> >
>>>>>>>> >> Router1(config)#*router ospf 55*
>>>>>>>> >> Router1(config-router)#*no discard-route internal*
>>>>>>>> >>
>>>>>>>> >>
>>>>>>>> >> Router1(config-router)#*no discard-route external*
>>>>>>>> >>
>>>>>>>> >> With the *internal* keyword, this command prevents the router
>>>>>>>> from
>>>>>>>> > automatically generating discard routes for internal summary
>>>>>>>> routes.
>>>>>>>> > Similarly, the *external *keyword is for external routes. However,
>>>>>>>> we urge
>>>>>>>> > caution with this command because the absence of a discard route
>>>>>>>> can cause
>>>>>>>> > loops.
>>>>>>>> >
>>>>>>>> >
>>>>>>>> >
>>>>>>>> > Thanking You
>>>>>>>> >
>>>>>>>> > Yours Sincerely
>>>>>>>> >
>>>>>>>> > Divin Mathew John
>>>>>>>> > divinjohn@gmail.com
>>>>>>>> > divin@dide3d.com
>>>>>>>> > +91 9945430983
>>>>>>>> > +91 9846697191
>>>>>>>> > +974 5008916
>>>>>>>> > PGP PUBLIC KEY BLOCK @
>>>>>>>> http://www.dide3d.com/divin_Public_PGP_key.txt
>>>>>>>> >
>>>>>>>> >
>>>>>>>> >
>>>>>>>> > On Mon, Mar 30, 2009 at 2:27 AM, Raghav Bhargava <
>>>>>>>> > raghavbhargava12@gmail.com> wrote:
>>>>>>>> >
>>>>>>>> >> Hi Experts,
>>>>>>>> >>
>>>>>>>> >> Have some doubts related to Null 0.
>>>>>>>> >>
>>>>>>>> >> In EIGRP,
>>>>>>>> >>
>>>>>>>> >> For example if we have 4 networks:-
>>>>>>>> >>
>>>>>>>> >> 1.1.0.1/24 , 1.1.1.1/24, 1.1.2.1/24, 1.1.3.1/24
>>>>>>>> >>
>>>>>>>> >> Now lets say I summarise them all under 1 default route by the
>>>>>>>> command ip
>>>>>>>> >> summary -address eigrp 10 0.0.0.0 0.0.0.0
>>>>>>>> >>
>>>>>>>> >> when I do this it creates a Null 0 route in the Routing table. So
>>>>>>>> If I
>>>>>>>> >> would
>>>>>>>> >> have not summarise these networks as a default route and would
>>>>>>>> have done
>>>>>>>> >> it
>>>>>>>> >> like this ip summary-address eigrp 10 1.1.0.0 0.0.3.255 .Then
>>>>>>>> will the
>>>>>>>> >> Null
>>>>>>>> >> 0 route be created.???? I don know..
>>>>>>>> >>
>>>>>>>> >> As per my understanding of Null 0 , it helps in preventing
>>>>>>>> forwarding
>>>>>>>> >> Loops
>>>>>>>> >> . So does it mean that if i want to reach a network which is
>>>>>>>> outside of
>>>>>>>> >> these 4 networks for eg - 4.4.4.4/24. The Null 0 will drop the
>>>>>>>> route for
>>>>>>>> >> this network. Please correct me if I am wrong.
>>>>>>>> >>
>>>>>>>> >> Secondly like in OSPF also when we do summarisation of internal
>>>>>>>> /external
>>>>>>>> >> routes a null 0 route is created. I know it is used for
>>>>>>>> preventing
>>>>>>>> >> forwarding loops but will it do the same thing . I mean if a
>>>>>>>> route for a
>>>>>>>> >> different network comes in will it drop it.
>>>>>>>> >>
>>>>>>>> >> Also in OSPF we can remove this Null 0 via the command---> no
>>>>>>>> >> discard-route
>>>>>>>> >> internal/external. Why do we do that if Null 0 helps in
>>>>>>>> preventing the
>>>>>>>> >> loops.
>>>>>>>> >>
>>>>>>>> >> Last but not the least is there a command to do the same in other
>>>>>>>> >> protocols
>>>>>>>> >> like RIP, EIGRP, BGP.
>>>>>>>> >>
>>>>>>>> >> just curiosu to know ....
>>>>>>>> >>
>>>>>>>> >>
>>>>>>>> >> --
>>>>>>>> >> Warm Regards
>>>>>>>> >> Raghav
>>>>>>>> >>
>>>>>>>> >>
>>>>>>>> >> Blogs and organic groups at http://www.ccie.net
>>>>>>>> >>
>>>>>>>> >>
>>>>>>>> _______________________________________________________________________
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>>>>>>>>
>>>>>>>>
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>>>>>>>>
>>>>>>>>
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>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Warm Regards
>>>>>> Raghav
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>
>
> --
> Warm Regards
> Raghav
Blogs and organic groups at http://www.ccie.net
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