Re: AS SET

this will come into action, if you have more than single exit point.

See this excellent example.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094826.shtml

On Sun, Mar 14, 2010 at 10:40 PM, Muzammil Malick <malickmuz_at_gmail.com>wrote:

> Thanks
>
> but how could this cause a loop?
> If the local router has a more specific route to a destination that is
> covered by the summary then it will use that.
>
> R1 ----------- R2
>
> If R1 advertises 10.0.0.1/24 to R2 and then R2 advertises back a summary
> for 10.0.0.0/16 without AS info. R2 has now covered many other prefixes
> which may have come
> from other AS' and even the prefix from R1, however if R1 has more specific
> routes it will use these. If it doesn't have more specific info then this
> will be its only route anyway so
> how can a loop be formed?
>
>
>
> On 14 March 2010 19:21, Nadeem Rafi <nrafia_at_gmail.com> wrote:
>
>> If i am wrong please correct me.
>>
>> when bgp is summarized then information for the routes being summarized is
>> lost. And summarizing AS is considered to be originator of this new route.
>> All the AS afterwards dont have knowledge of routes being summarized that
>> from which AS they belong. And this can led from non-optimal routing to
>> routing loops, because of this as-set is used to feed with
>> more information about routes being summarized.
>>
>>
>>
>> HTH
>>
>> On Sun, Mar 14, 2010 at 10:12 PM, Muzammil Malick <malickmuz_at_gmail.com>wrote:
>>
>>> Hi
>>>
>>> Could someone please help me out and explain why you would include AS
>>> information in a bgp summary (aggregate-address 10.0.0.0 255.255.0.0
>>> summary-only as-set)
>>>
>>> I know what it does and how to use it but why from a design perspective
>>> would you want to send AS information as apart of a summary.
>>> Can someone provide an example?
>>>
>>>
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Received on Sun Mar 14 2010 - 23:31:20 ART