Re: [Isis-wg] Reg: draft-ietf-isis-reverse-metric-03

Hi Vijay,

Please see below.

On Jun 13, 2013, at 1:18 AM, Vijay Kumar Vasantha <vvasanth@Brocade.com> wrote:
> Hi,
>  
> While reading draft-ietf-isis-reverse-metric-03 I got the following query, could someone please clarify it.
>  
> -          Could the link to DIS be made link of last resort on a LAN.
>  
>  
> For example consider a topology where three routers A, B & C are connected on a LAN, where A is DIS.
>  
> A----------A’-----------B
>                     |
>                     |
>                     |
>                    C

I take it A' represents the pseudo-node?

> If administrator wishes to remove the bi-directional traffic for node A, then configuring reverse-metric on A will,
>  
> -          Make the cost from A to A’ high.
> -          Not affect the cost from A’ to A in pseudo-node LSP.

The latter bullet is incorrect for the scenario you describe.  The DIS should increase the cost in the pseudo-node LSP (A') back to A, at the same time.  But, before you answer, please see the next response.

> So the traffic from non-DIS nodes could still reach DIS on this LAN.
>  
> Perhaps one of the ways to address it would be,
> Upon administrator enabling reverse-metric on a LAN,
> -          If the node is a DIS on the LAN then DIS could increase the cost to itself in the pseudonode LSP.

Actually, I believe the comment/question you have is actually more applicable to a related draft:
http://tools.ietf.org/html/draft-ietf-isis-oper-enhance-03

In particular, you may wish to review Section 3, "Pseudonodes with Non-zero Metrics", of the aforementioned draft, which describes where the DIS, itself, is altering the metric in the Pseudo-node LSP to achieve the effect you describe.

Anyway, let me know if the above addresses you question or not.

Thanks,

-shane

> Thanks,
> Vijay
>  
>  
>  
>  
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