From: Ronnie Angello (ronnie.angello@gmail.com)
Date: Fri Jan 23 2009 - 17:00:32 ARST
As long as a feasible successor exists, EIGRP will not go active on
the route and will start using the feasible successor immediately.
That behavior is independent of how links are addressed. I don't
recall seeing a requirement that the link has to be within the same
address space. That's news to me so I was trying to figure out
exactly why.
The only thing that I can think of is that the whole point of the
summary is to contain the query scope. If the distribution link is
within the range of the summary, then it's advertised to the core as
part of the summary and you don't have to worry about the rest of the
network being queried if that link fails.
On Fri, Jan 23, 2009 at 1:53 PM, ISolveSystems
<support@isolvesystems.com> wrote:
> But even if the p2p link between the dist switches is NOT within the range
> that's being summarized, why is there a need for convergence for the p2p
> link IP address when the access layer link is failing (not the P2P link)?
> The query will not go out for the p2p link, but just for the access-layer
> subnet, right?
>
> Thanks.
>
> On Fri, Jan 23, 2009 at 11:21 AM, Pavel Bykov <slidersv@gmail.com> wrote:
>
>> Because otherwise you wouldn't be able to reroute traffic from the right
>> distribution switch to the access immediately - you would have to wait for
>> IGP convergence.
>> If ptp link between distribution switches is WITHIN the range that is being
>> summarized, you don't wait for a convergence, and use feasible successor
>> route INSTANTENEOUSLY
>>
>> On Wed, Jan 21, 2009 at 10:30 PM, ISolveSystems <support@isolvesystems.com
>> > wrote:
>>
>>> I am reading the campus network design guide.
>>>
>>>
>>> http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/HA_campus_DG/hacampusdg.html
>>>
>>>
>>>
>>> See the paragraph below. Why does the address space selected for the
>>> distribution-to-distribution link must be within the address space being
>>> summarized to be effective?
>>>
>>>
>>>
>>> "Because the distribution nodes send summarized information towards the
>>> core, an individual distribution node does not advertise loss of
>>> connectivity to a single VLAN or subnet. This means that the core does not
>>> know that it cannot send traffic to the distribution member where the link
>>> has failed. Adding an L3 link between the distribution switches allows the
>>> distribution node that loses connectivity to a given VLAN or subnet to
>>> reroute traffic across the distribution-to-distribution link. The address
>>> space selected for the distribution-to-distribution link must be within
>>> the
>>> address space being summarized to be effective."
>>>
>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>> _______________________________________________________________________
>>> Subscription information may be found at:
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>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>> --
>> Pavel Bykov
>> ----------------
>> Don't forget to help stopping the braindumps, use of which reduces value of
>> your certifications. Sign the petition at http://www.stopbraindumps.com/
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
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>
>
>
>
>
>
>
>
-- Ronald Angello CCIE #17846Blogs and organic groups at http://www.ccie.net
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