Re: [Isis-wg] Comments on draft-xu-isis-flooding-reduction-in-msdc-00

Erik Auerswald <> Tue, 25 April 2017 10:26 UTC

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Date: Tue, 25 Apr 2017 12:26:17 +0200
From: Erik Auerswald <>
To: Xuxiaohu <>
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Subject: Re: [Isis-wg] Comments on draft-xu-isis-flooding-reduction-in-msdc-00
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Hi Xiaohu,

please see my response inline (content not relevant to this
response removed).

On Tue, Apr 25, 2017 at 08:46:06AM +0000, Xuxiaohu wrote:
> > -----邮件原件-----
> > 发件人: Erik Auerswald []
> > This idea can be realized using existing implementations, with additional
> > possible optimizations via IS-IS extensions. In fact I built a lab today to play with
> > the idea, using a couple of switches, one of which was used as controller, and
> > the others as fabric switches.
> It would be great if you could share more information about your experiment:)

Nothing big, I just took four Extreme Networks X460[-G2] switches from
the company lab, connected three switches in a row to build the "fabric"
(you could think of the middle one as "spine" and the two at the ends
as "leafs"), and then connected the fourth switch to all three "fabric"
switches to act as "controller". I then configured IS-IS on the switches,
configured a high metric on the links to/from the "controller" switch,
and used the "meshBlocked" attribute from RFC 2973 to restrict flooding
inside the "fabric." To do this I configured "meshBlocked" on all links
between "fabric" switches.

Show outputs for transmitted LSPs showed flooding reduction (e.g. when
adding a new loopback interface on a "leaf" switch), with full IP
connectivity over the fabric. The "management" links to the "controller"
were not used for "leaf" to "leaf" traffic due to the higher metric.

> > RFC 2973, IS-IS Mesh Groups, can be used to prevent flooding on the data path
> > links.
> Could you explain more about how to apply the ISIS mesh group in the CLOS topology?

Please see above. RFC 2973 describes a method to configure individual links
to inhibit flooding of LSPs using the "meshBlocked" attribute.

Dipl.-Inform. Erik Auerswald T:+49-631-4149988-0 M:+49-176-64228513

Gesellschaft für Fundamental Generic Networking mbH
Geschäftsführung: Volker Bauer, Jörg Mayer
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