RFC 3021 (rfc3021) - Page 5 of 10

Using 31-Bit Prefixes on IPv4 Point-to-Point Links

Alternative Format: Original Text Document


RFC 3021             31-Bit Prefixes on IPv4 Links         December 2000


3. Recommendations

   The considerations presented in Section 2 affect other published
   work.  This section details the updates made to other documents.

3.1. "Requirements for Internet Hosts -- Communication Layers" [RFC 1122]

   Section 3.2.1.3 (e) is replaced with:

      (e)  { , , -1 }

         Directed broadcast to the specified subnet.  It MUST NOT be
         used as a source address, except when the originator is one of
         the endpoints of a point-to-point link with a 31-bit mask.

   A new section (numbered 3.2.1.3 (h)) is added:

      (h)  { , , 0 }

         Subnetwork number.  SHOULD NOT be used as a source address,
         except when the originator is one of the endpoints of a point-
         to-point link with a 31-bit mask.  For other types of links, a
         packet with such a destination SHOULD be silently discarded.
         If these packets are not silently discarded, they MUST be
   treated
         as IP broadcasts [RFC 1812].

3.2. "Assigned Numbers" [RFC 1700]

   Sub-section (e) of the "Special Addresses" section in the
   "Introduction" is replaced with:

      (e)   {, , -1}

         Directed broadcast to specified subnet.  Can only be used as a
         destination address.  However, in the case where the originator
         is one of the endpoints of a point-to-point link with a 31-bit
         mask, it can also be used as a source address.

3.3. "Requirements for IP Version 4 Routers" [RFC 1812]

   Section 4.2.2.11 (d) is replaced with:

      (d) { , -1 }

         Directed Broadcast - a broadcast directed to the specified
         network prefix.  It MUST NOT be used as a source address,
         except when the originator is one of the endpoints of a point-



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