Router-to-router operation !!

[Atsushi Iwata <[e-mail]>]

ROLC working group members,

Though I thought that there have been the same kind of discussions,
unfortunately I cannot understand clearly why and when
router-to-router problems occur, in the "draft-ietf-rolc-nhrp-03.txt". 
Could anyone please show me an abstract example with figures ?

>>8.1 Router-to-Router Operation
>>
>>   In practice, the initiating and responding stations may be either
>>   hosts or routers.  However, there is a possibility under certain
>>   conditions that a stable routing loop may occur if NHRP is used
>>   between two routers.  This situation can be avoided if there are no
>>   "back door" paths between the entry and egress router outside of the
>>   NBMA network, and can be ameliorated by periodically reissuing the
>>   NHRP request.  If these conditions cannot be satisfied, the use of
>>   NHRP between routers is not recommended.
>>
>>   One approach to the router-to-router case that is being considered is
>>   to run a limited instance of a routing protocol between the two
>>   routers.  Any routing protocol that provides loop detection may be
>>   used.  This routing protocol instance will likely only carry a subset
>>   of the total routing information, and is unlikely to be closely
>>   integrated into the routing in which each of the routers is otherwise
>>   participating (due to the abitrary connectivity possible in such
>>   situations and its impact on the stability and quality of overall
>>   routing).  This approach is for further study.

Thank you.

  ***------------------------------------------------------------***
     Atsushi Iwata  Network Research Lab., C&C Research Labs.,NEC
	4-1-1 Miyazaki Miyamae-ku Kawasaki Kanagawa, JAPAN 216
Tel:[phone], Fax:[phone],E-Mail:[e-mail]