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Re: [Lsr] Question about OSPF (transit area routing loop)

"Acee Lindem (acee)" <acee@cisco.com> Thu, 05 March 2020 22:38 UTC

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From: "Acee Lindem (acee)" <acee@cisco.com>
To: Sergey SHpenkov <sergey.v.shpenkov@gmail.com>, "lsr@ietf.org" <lsr@ietf.org>
Thread-Topic: [Lsr] Question about OSPF (transit area routing loop)
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Date: Thu, 05 Mar 2020 22:38:15 +0000
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Subject: Re: [Lsr] Question about OSPF (transit area routing loop)
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Hi Sergey, OSPF adherents,
I think what you are proposing is that ASBR 3 prefers an inter-area path over a transit area over an intra-area backbone path (irrespective of cost). That was solve this problem – trying to think if it would create any. I’ve included the network topology again for reference.

Others, please chime in..
[A screenshot of a video game  Description automatically generated]
Thanks,
Acee

From: Sergey SHpenkov <sergey.v.shpenkov@gmail.com>
Date: Wednesday, March 4, 2020 at 6:05 AM
To: Acee Lindem <acee@cisco.com>, "lsr@ietf.org" <lsr@ietf.org>
Subject: Re: [Lsr] Question about OSPF (transit area routing loop)

Hi Acee,

Fixed errata in a previous my post.

To solve this problem, before starting 16.3, it is possible that all ABR
routers (virtual endpoints) should update the cost of routes for all ASBRs (if
these routes exist in the backbone area) from all virtual neighbors in the
transit area, regardless of whether these costs have been improved or
worsened.

For example, router ABR_3 first checks sumLSA-4 from virtual neighbor ABR_1
in the transit area 0.0.0.200 and updates the cost for ASBR to 300 in the
backbone area. After that, the calculation begins on the router ABR_3 16.3.

It is a bad idea?

Thanks,
Sergey

вт, 3 мар. 2020 г. в 21:58, Sergey SHpenkov <sergey.v.shpenkov@gmail.com<mailto:sergey.v.shpenkov@gmail.com>>:
Hi Acee,

To solve this problem, before starting 16.3, it is possible that all ABR routers (virtual endpoints) should update the cost of routes for ABRS (if these routes exist in the backbone area) from all virtual neighbors in the transit area, regardless of whether these costs have been improved or worsened.

For example, router ABR_3 first checks sumLSA-4 from virtual neighbor ABR_1 in the transit area 0.0.0.200 and updates the cost for ABRS to 300 in the backbone area. After that, the calculation begins on the router ABR_3 16.3.

It is a bad idea? :)

Thansk,
Sergey

пн, 2 мар. 2020 г. в 00:51, Acee Lindem (acee) <acee@cisco.com<mailto:acee@cisco.com>>:
Hi Sergey,
Seems it is a real problem that needs a solution. Let’s continue the discussion.
Thanks,
Acee

From: Sergey SHpenkov <sergey.v.shpenkov@gmail.com<mailto:sergey.v.shpenkov@gmail.com>>
Date: Sunday, March 1, 2020 at 4:41 PM
To: Acee Lindem <acee@cisco.com<mailto:acee@cisco.com>>
Subject: Re: [Lsr] Question about OSPF (transit area routing loop)

Hi Acee,

Please tell me the discussion on the topic of "Question about OSPF (transit area routing loop)" can be considered complete?

Thanks,
Sergey

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