RFC 1923 (rfc1923) - Page 2 of 3

RIPv1 Applicability Statement for Historic Status

RFC 1923   RIPv1 Applicability Statement for Historic Status  March 1996


   that the mask used locally is the correct mask to apply for all
   subnets of that network.

   This has a number of effects.

   1) RIPv1 can not be used with variable length subnetting.  In the
      presence of variable length subnetting it will consistently
      misinterpret prefix lengths.

   2) RIPv1 is difficult to use with supernetting.  All CIDR supernets
      must be exploded and advertised to RIPv1 as individual "natural"
      classful advertisements.

   3) Even when the networks running RIPv1 are themselves only subnetted
      in fixed ways, if the remainder of the network has variable
      subnetting then one must carefully make sure that RIPv1 does not
      destroy the mask information when it passes through those subnets
      running RIPv1.  Put another way, co-existence with mutual
      information exchange between RIPv1 and more advanced routing
      protocols is problematic at best.  Note that this applies even when
      the other routing protocol is RIPv2.

   4) The Internet will soon be making use of addresses which appear to
      RIPv1 to be parts of Class A networks. Networks using RIPv1 may not
      be able to reach all sites assigned the subsections of a single A.

2.2 Simple Distance Vector

   RIPv1 is a simple distance vector protocol.  It has been enhanced
   with various techniques, including Split Horizon and Poison Reverse
   in order to enable it to perform better in somewhat complicated
   networks.

   However, being a simple distance vector protocol, it will run into
   difficulty. First and foremost, it will occasionally have to count to
   infinity in order to purge bad routes.  This delays the convergence
   of routing.  In order to keep this short, RIPv1 defines infinity as
   16 hops.  That means that networks with diameters larger than that
   can not use RIP.  Even getting close to that limit can cause
   confusion for some implementations.

3.0 Conclusion

   The recommendation of this Applicability statement is that if there
   is reason to run RIP in a network environment, one should use RIPv2
   (RFC 1723).





Halpern & Bradner            Informational