RFC 1879 (rfc1879) - Page 2 of 6

Class A Subnet Experiment Results and Recommendations

RFC 1879               Class A Subnet Experiment            January 1996


   Initial predictions [3] seemed to indicate that the safest path for
   an ISP that participates in such a routing system is to have -all- of
   the ISP clients be either:

                a) singly connected to one upstream ISP
        OR
                b) running a classless interior routing protocol

   It is also noted that a network with default route may not notice it
   has potential routing problems until it starts using subnets of
   traditional A's internally.

Problems & Solutions

Operations

   There were initial problems in at least one RIPE181 [4]
   implementation.  It is clear that operators need to register in the
   Internet Routing Registry (IRR) all active aggregates and delegations
   for any given prefix.  Additionally, there need to be methods for
   determining who is authoritative for announcing any given prefix.

   It is expected that problems identified within the confines of this
   experiment are applicable to some RFC 1597 prefixes or any "natural"
   class "A" space.

   Use of traceroute (LSRR) was critical for network troubleshooting
   during this experiment. In current cisco IOS, coding the following
   statement will disable LSRR and therefore inhibit cross-provider
   troubleshooting:

                no ip source-route

   We recommend that this statement -NOT- be placed in active ISP cisco
   configurations.

   In general, there are serious weaknesses in the Inter-Provider
   cooperation model and resolution of these problems is outside the
   scope of this document. Perhaps the IEPG or any/all of the national
   or continental operations bodies [5] will take this as an action item
   for the continued health and viability of the Internet.










Manning                      Informational