RFC 5302, "Domain-Wide Prefix Distribution with Two-Level IS-IS", October 2008

Errata ID: 3994
Status: Verified
Type: Technical
Publication Format(s) : TEXT
Reported By: Amit Kalita
Date Reported: 2014-05-20
Verifier Name: Alia Atlas
Date Verified: 2014-06-10

Section 3.1 says:

L2->L1 inter-area external routes with external metric:  These are
      advertised in L1 LSPs, in TLV 130.  The up/down bit is set to one,
      metric-type is external metric.  These IP prefixes are learned via
      L2 routing, and were derived during the L1 SPF computation from
      prefixes advertised in L2 LSPs in TLV 130 with external metrics.

It should say:

L2->L1 inter-area external routes with external metric:  These are
      advertised in L1 LSPs, in TLV 130.  The up/down bit is set to one,
      metric-type is external metric.  These IP prefixes are learned via
      L2 routing, and were derived during the L2 SPF computation from
      prefixes advertised in L2 LSPs in TLV 130 with external metrics.

Notes:

The following part has been corrected:

"These IP prefixes are learned via
L2 routing, and were derived during the L1 (should be L2) SPF computation from
prefixes advertised in L2 LSPs in TLV 130 with external metrics."

The IP prefixes which are learned via L2 routing were derived during L2 SPF computation instead of L1 SPF computation from prefixes advertised in L2 LSPs. As these prefixes were originally advertised in L2 area hence the SPF for these prefixes should run on the L2 LSPs and eventually the prefixes derived through L2 LSP should be leaked into L1 area.

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