shen,

  If a router has no adjacency on a broadcast/NBMA
  interface, it includes a type-2 link into its router-LSA
  to announce the associated subnet.

--
Alex Zinin
Monday, July 23, 2001, 8:28:05 PM, shen jing wrote:
> Alex,
> Thank you very much.
> But, what do you means  "Routing  to the destinations on the segment
> itself will proceed as usual"?
> If the network does not appear in LSAs of router attached to it,  I think
> the network graph in router
> will not include such a network.  Will each router attached to the
> network  add a direct connectionn
> item for each port's subnet ?  how will other routers , which is not
> directly connected to it
> , know the existence of the network ?  I think even those routers who is
> directly connected to
> such a network can forward packet to those host on the subnet, other
> router will not be able to do
> the same.
> Would  you please give more hints on this question?
> Jing Shen
>> Jing,
>>
>>   First off, note that normally, there will be at
>>   list the DR on the segment and the situations where
>>   a segment does not have any DR is either a configuration
>>   mistake (all routers have priority 0) or transient (the DR/BDR
>>   has not accepted its responsibilities yet).
>>
>>   Nevertheless, if there's no DR/BDR on a segment, no adjacencies
>>   will be established btw the router attached to it, the network
>>   will not be announced in the routers' LSAs, and, as a consequence,
>>   it will not be used as a transit element by the routers. Routing
>>   to the destinations on the segment itself will proceed as usual,
>>   however.
>>
>> -

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