RFC 2336 (rfc2336) - Page 2 of 5

Classical IP to NHRP Transition

RFC 2336         Classical IP and ARP over ATM to NHRP         July 1998


   It is reasonable to expect that ATMARP Clients and NHRP Clients will
   initially coexist within a LIS.  Thus, it is necessary to define a
   graceful transition, including a period of coexistance, from the use
   of ATMARP to the use of NHRP for address resolution in the LIS
   [1][2]. In short, NHSs will be required to respond to ATMARP Client
   queries in a fashion which will permit continued use of the ATMARP
   Client within the LIS during the ATMARP to NHRP transition period.
   Note that this document places no protocol requirements upon
   ATMARP[1] servers.

   For the following, it will be assumed that the reader is familiar
   with the terminology as described in [1][2][3].

2. Service Requirements

   If NHRP is to be used in a LIS then only NHSs will be used in the
   LIS; that is, there will not be a mixture of NHSs and ATMARP servers
   within the same LIS.  Since ATMARP servers will not be able to
   understand NHCs and since, as described below, NHSs will respond to
   ATMARP Clients, this is a reasonable simplifying restriction.

   This document will only address SVC based environments and will not
   address PVC environments.  This document will refer only to ATM AAL5
   as the NBMA and IP as the protocol layer since ATMARP only addresses
   these protocols.

2.1 NHRP Server Requirements

   If NHRP Servers (NHS) are to be deployed in a LIS which contains both
   ATMARP Clients and NHRP Clients then NHSs MUST respond to
   ATMARP_Requests sent by ATMARP Clients in the same fashion that an
   ATMARP Server would respond as described in [1].  To do this, the NHS
   MUST first recognize the LLC/SNAP ATMARP code point with LLC=0xAA-
   AA-03, OUI=0x00-00-00, and ethertype=0x08-06.  Further, the NHS MUST
   recognize the packet formats described in Section 8.7 of [1].
   However, since this document does not extend to PVC environments,

   NHSs MUST only receive/respond to values of ar$op of 1,2,10
   (Decimal).  If an NHS receives an ATMARP message with ar$op values
   other than those previously noted then the NHS MUST discard the
   packet and MUST NOT take any further action.

   When an NHS receives a valid (as defined in the previous paragraph)
   ATMARP_Request packet, the NHS MUST follow the rules described in
   Section 8.4 of [1] with the following additional processing:






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