From: Salah ElShekeil (salah.elshekeil@gmail.com)
Date: Sun Mar 29 2009 - 18:57:11 ART
also in eigrp you can remove route to null 0!!!
it a machnism in the router itself to provent the loops in the network,
by descarding the traffic which the router have no longer match for,
if you want to froward the traffic even the router have to longer match for
you can remove the null 0,
but make sure this will not affect your network,
On Sun, Mar 29, 2009 at 11:57 PM, 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
>
>
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