From: Divin Mathew John (divinjohn@gmail.com)
Date: Sun Mar 29 2009 - 19:12:11 ART
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
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