[c-nsp] Rationale for ISIS default origination behavior

Mark Tinka mark.tinka at seacom.mu
Wed Jun 19 04:18:41 EDT 2013


On Monday, January 21, 2013 09:31:02 PM David Barak wrote:

> There are most certainly those of us who do make use of
> the L1/L2 injection of the default route via ATT bit in
> ISIS networks today.  It's an extremely useful way to
> keep a L2 database down in size when you don't need to
> have many areas.

The problem comes in when you have other protocols on the 
router that require the specific /32 (IPv4) or /128 (IPv6).

Otherwise, yes, the Attached Bit does have use-cases, as it 
was designed for. The theory is that L1/L2 routers know how 
to get to the L2 domain, where all knowledge about the 
network presumably lies. In our case, that is quite a thumb-
suck :-).

Mark.
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