[Xorp-users] [GEN] query-> OSPF (waiting for your Answers)

[karnik]

      Query : While Calculating cost only calculate cost For Router to
      Network not for Network to router why?


*Example: *Consider the following *scenario and Figure A*
For RTA router if it wants to send  packet to  RTB  Cost = 10
why not , cost = 18 ?
If u have answer please tell me............


      Shortest Path Tree

Assume we have the following network diagram with the indicated 
interface costs. In order to build the shortest path tree for RTA, we 
would have to make RTA the root of the tree and calculate the smallest 
cost for each destination.

spf1.gif

*                                     figure A*

The above is the view of the network as seen from RTA. Note the 
direction of the arrows in calculating the cost. For example, the cost 
of RTB's interface to network 128.213.0.0 is not relevant when 
calculating the cost to 192.213.11.0. RTA can reach 192.213.11.0 via RTB 
with a cost of 15 (10+5). RTA can also reach 222.211.10.0 via RTC with a 
cost of 20 (10+10) or via RTB with a cost of 20 (10+5+5). In case equal 
cost paths exist to the same destination, Cisco's implementation of OSPF 
will keep track of up to six next hops to the same destination.

After the router builds the shortest path tree, it will start building 
the routing table accordingly. Directly connected networks will be 
reached via a metric (cost) of 0 and other networks will be reached 
according to the cost calculated in the tree.

-- 
_____________________________________________________________________
Disclaimer: This e-mail message and all attachments transmitted with it
are intended solely for the use of the addressee and may contain legally
privileged and confidential information. If the reader of this message
is not the intended recipient, or an employee or agent responsible for
delivering this message to the intended recipient, you are hereby
notified that any dissemination, distribution, copying, or other use of
this message or its attachments is strictly prohibited. If you have
received this message in error, please notify the sender immediately by
replying to this message and please delete it from your computer. Any
views expressed in this message are those of the individual sender
unless otherwise stated.Company has taken enough precautions to prevent
the spread of viruses. However the company accepts no liability for any
damage caused by any virus transmitted by this email.
__________________________________________________________________________