RFC Errata


Errata Search

 
Source of RFC  
Summary Table Full Records

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

Source of RFC: isis (rtg)

Errata ID: 1541
Status: Held for Document Update
Type: Editorial
Publication Format(s) : TEXT

Reported By: Alfred Hoenes
Date Reported: 2008-10-08
Held for Document Update by: Adrian Farrel
Date Held: 2012-08-09

Section 3.1,1st para says:

   The combination IP Internal Reachability Information and external
   metric-type is not allowed.  Also, the up/down bit MUST NOT be set in
|  L2 LSPs.  This leaves us with 8 different types of IP advertisements
|  in IS-IS.  However, there are more than 8 reasons for IP prefixes to
   be advertised in IS-IS.  The following list describes the types of IP
   prefixes and how they are encoded.

It should say:

   The combination IP Internal Reachability Information and external
   metric-type is not allowed.  Also, the up/down bit MUST NOT be set in
|  L2 LSPs.  This leaves us with 9 different types of IP advertisements
|  in IS-IS.  However, there are more than 9 reasons for IP prefixes to
   be advertised in IS-IS.  The following list describes the types of IP
   prefixes and how they are encoded.

Notes:

Rationale:
Each of the two restrictions mentioned in the initial part
of the quoted paragraph indeed excludes 4 possibilities
of the original set of 16 combinations. However, these
restrictions are not exclusive; they overlap in one case,
thus reducing the number of forbidden combinations to 7.

Therefore, we are left with *9* different types of combinations.

This can also be seen from the subsequent list of 12 items
(unfortunately, the numbering of these has been lost on the way
from RFC 2966 to its successor). That list contains 3 pairs of
entries, i.e. 6 entries that contain the wording
"These prefixes cannot be distinguished from ... routes." ,
thus reducing the number of distinguishable cases from 12 to 9.

Virtually restoring the list item numbering as (1) ... (12),
the following table shows a decision matrix:

+----------------------+---------------+-------------------+
| Metric U/D \ Level | L1 | L2 |
| Type Bit \ TLV# | 128 | 130 | 128 | 130 |
+----------------------+-------+-------+---------+---------+
| 0 | (1) | (2) | (3),(5) | (4),(6) |
| Int --------------+-------+-------+---------+---------+
| 1 | (7) | (8) | N/A | N/A |
+----------------------+-------+-------+---------+---------+
| 0 | N/A | (9) | N/A |(10),(11)|
| Ext --------------+-------+-------+---------+---------+
| 1 | N/A | (12) | N/A | N/A |
+----------------------+-------+-------+---------+---------+

Report New Errata