Class A Subnet Experiment Results and Recommendations
RFC 1879

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Network Working Group                                 B. Manning, Editor
Request for Comments: 1879                                           ISI
Category: Informational                                     January 1996

                       Class A Subnet Experiment
                      Results and Recommendations

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Discussion/Purpose

   This memo documents some experiences with the RFC 1797 [1] subnet A
   experiment (performed by the Net39 Test Group (see credits)) and
   provides a number of recommendations on future direction for both the
   Internet Registries and the Operations community.

   Not all proposed experiments in RFC 1797 were done. Only the "case
   one" type delegations were made.  Additional experimentation was done
   within the DNS service, by supporting a root nameserver and the
   primary for the domain from within the subnetted address space.  In
   addition, testing was done on classless delegation [2].

   Internet Services offered over the RFC 1797 experiment were:

         Finger
         HTTP
         Telnet
         FTP server/client
         Gopher
         kerberos
         lpr (and its ilk)
         X
         DNS

   F.Root-Servers.Net, a root name server had an interface defined as
   part of the RFC 1797 experiment.  Attached is a report fragment on
   it's performance: "My root server has processed 400,000,000 queries
   in the last 38 days, and well over half of them were to the temporary
   39.13.229.241 address (note that I retained the old 192.5.5.241
   address since I knew a lot of folks would not update their root.cache
   files and I didn't want to create a black hole.)" - Paul Vixie

Manning                      Informational                      [Page 1]
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                      [Page 2]
RFC 1879               Class A Subnet Experiment            January 1996

Routing

   A classic cisco configuration that has the following statements

                ip route 39.1.28.0 255.255.255.0
                router bgp 64000
                redistribute static

   will, by default, promote any classful subnet route to a full
   classful route (supernet routes will be left alone).  This behaviour
   can be changed in at least the following two ways:

        1:
                ip route 39.1.28.0 255.255.255.0
                router bgp 64000
                no auto-summary
                redistribute static

        2:
                ip route 39.1.28.0 255.255.255.0
                router bgp 64000
                network 39.1.28.0 mask 255.255.255.0
                redistribute static route-map static-bgp
                ....
                access-list 98 deny 39.1.28.0 0.255.255.255
                access-list 98 permit any
                ....
                route-map static-bgp
                match ip address 98

   Users of cisco gear currently need to code the following two
   statements:

                ip classless
                ip subnet-zero