Re: Route summarisation and discard route.

Thanks Adam, great answers.

On Mon, May 30, 2011 at 11:05 PM, Adam Booth <adam.booth_at_gmail.com> wrote:

> Hi Jacek,
>
> 1) With EIGRP, when you create the summary route, at the end of the
> definition, you can set the admin distance of the discard route - if you
> wish for the router not to have the discard route, just set the admin
> distance to 255.
>
> 2) I'm not sure about this one, I'm guessing in part because of the
> classful heritage of RIP, when you specify which networks to advertise into
> RIP, you the configuration uses classful networks even if you have "no
> auto-summary" and the prefixes being exchanged between neighbors are
> classless.
>
> 3) There is a potential risk of introducing routing loops if you provide
> aggregation facilities and for instance have a default route pointing back
> towards the source of the traffic, rather than waiting to the IP packet's
> TTL to expire, a discard route is a good "trap"
>
> Cheers,
> Adam
>
>
> On Tue, May 31, 2011 at 12:45 PM, Jacek <q.192.168.1.0_at_gmail.com> wrote:
>
>> Hello experts,
>> I have questions about route summarisation and I am wondering why it
>> behaves
>> differently in different routing protocols.
>>
>> In OSPF discard route is installed automatically and there is a command to
>> remove it: "no discard-route internal" and "no discard-route external"
>> In EIGRP discard route is installed automatically but there is no command
>> to
>> remove it.
>> Question 1: Why OSPF provides way to remove discard route but not EIGRP.
>> Is
>> there a deep reason for that ?
>>
>> In RIPV2 discard route is not installed automatically.
>> Question 2: Why there is no discard route in RIP ?
>> Question 3: Should a discard route be installed manually in RIP ? I mean
>> as
>> a best practice, not in the Lab.
>>
>> Thanks,
>>
>>
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Received on Tue May 31 2011 - 08:41:03 ART