The IP Over NBMA (ION) Archive

["James V. Luciani" <luciani@BayNetworks.com>]

Luca,

> My first guess was that, as "normal" configuration all the router on the
> NBMA net are NHS. In chapter 4 a more general scenario is depicted: the
> NHS is a distinct network element and the NHCs are configured with the
> "local NHS" to which send queries. (This may lead to have an network of
> NHSs overlaied to the network of router).
> If this is correct isn't there an error  in the "Protocol overview"
> (section 2.2 page 5-6)? It seems to suggest that the NHRP-query shall be
> sent to the first router along the catenet path toward the destination:
IMHO, a router/route-server is an NHS but an NHS need not be a 
router/route-server although an NHS must be aware in some sense of a
"routed path".  Further, keep in mind that not everyone has only one router
per LIS/LAG so that it is perfectly reasonable to expect to see a 
NHC configured with the NBMA address of multiple routers/NHS; the default
case is of course the default router/NHS.
There is no intended implication of there being an overlay beyond tthat
of the routed infrastructure since this disappeared with Server Mode in v4/v5.

> In addition: what if the next hop is NOT reachable?
The following is from page 30:

       6 - Protocol Address Unreachable

         This error occurs when a packet it moving along the routed path
         and it reaches a point such that the protocol address of
         interest is not reachable.


Hope this is useful to you.
Regards,
--Jim Luciani
__________________________________________________________________________
James V. Luciani                                   luciani@baynetworks.com
Bay Networks, Inc.                                  voice: +1 508 439-4734
3 Federal St., BL3-04                               fax:   +1 508 670-8153
Billerica, MA 01821