MBGP translate-update Feature
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			       04/12/99

The MBGP translate-update feature is used to transition older BGP-only clouds 
to an MBGP infrastructure. The scenario this feature is used is typically in 
an MBGP capable router which peers with a customer site which has a BGP-only 
capable router. That is, the customer site has not or cannot upgrade the 
router to a MBGP capable image.

If the customer site desires to have its own sources send multicast traffic,
route prefixes which represent those sources must be advertised into the MBGP
infrastructure. However, since the customer site cannot originate MBGP
advertisements, the router that it peers with will translate the BGP prefixes
into MBGP prefixes.

Nothing explicit has to be configured on the customer BGP router. On the router
the customer site router BGP peers with, the following configuration commands
are used:

    router bgp <isp-as>
    neighbor <customer-router> remote-as <customer-as>
    neighbor <customer-router> translate-update [nlri multicast unicast]

A router with the above configuration will do the following when it receives
a BGP Update from <customer-router>:

o If "nlri multicast" is configured on the translate-update command, the
  router will take each prefix from the BGP Update message and translate it
  to MBGP format. That is, each reachable prefix in the BGP Update will be
  moved to the MP_REACH_NLRI attribute and each prefix in the withdrawal 
  section of the BGP Update will be moved to the MP_UNREACH_NLRI attribute.
  This newly formatted Update message will be passed to the Update processor
  allowing the local router to think that multicast NLRI were sent by the
  peer.
o If "nlri multicast unicast" is configured, the above step is performed as
  well as passing the original BGP Update to the Update processor. Thereby,
  allowing the local router to think that the peer sent it both unicast and
  multicast annoucements for the same prefixes. This is the default setting
  when the "nlri" keyword is not used.

When translating an unicast encoded Update, if the Next-Hop attribute is
supplied, the translation process will copy such a value to the MP_REACH_NLRI
attribute.

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