Vikas

I'm not familiar with the BSD code either but this is the way it should work
in order to build the routing table a router should first calculcate the path (
outgoing interface, nexthop ) to all the node ( router and Transit netwrok ).
IP address is just part of the node information and is tied to the directed
graph now when a router ( root ) built the SPT it will find a node in the
shortest path list for every iteration and when this node is router node ABR ( B
bit set ) or ASBR ( E bit set ) it will save it as a "router route " and will
use it later in order to calculate the path ( outgoing interface and next hop )
for type 3 or type 5 LSA. when the node is a transit netwrok it will install the
IP address of the netwrok in the routing table by masking the LS ID of type 2 (
DR ip address ) with the mask in the body of the LSA
note that for router type node the IP address ( stub link information ) is
installed once the SPT is built up and in a second step of the process

Sina

"Xie, Feng" wrote:

> Vikas:
>
> I am not familiar with ospf code in BSD. I guess they want to keep track
> of the reachability of ABRs and ASBRs for calculating inter-area and
> inter-AS routes. They may keep some "fake" routing tables for ASBRs and ABRs
> for this purpose. These routing tables may not be used for forwarding
> packets. If my assumption is correct, they use ABR, ASBR or Transit Networks
> to decide to which table they will insert the entry. If so, Transit Network
> there simply means all other prefixes than ASBR or ABR. Again, the above
> explanation is just my guess. Hopefully, someone who knows ospf in BSD will
> give a better explanation.
>
> Feng Xie
>
> -----Original Message-----
> From: Vikas B. Wadhwani [mailto:wvikasyahoo.com]
> Sent: Tuesday, July 17, 2001 2:48 PM
> To: feng.xiemarconi.com
> Subject: Re: Topology Info
>
> Feng,
> Thanks for the response. I am aware that the packets
> are delivered to an interface rather than to the
> router id. I am looking at the free bsd code. In there
> after having found the route to a destination, when
> they have to make an entry into the routing
> table,there are functions to make entries into the
> routing table based on whether the node is an ABR,ASBR
> or a transit network. This set me wondering as to what
> my node type really is since they are connected by PPP
> links and are also hosts(source and sinks for
> packets). Im still trying to figure out.What do you
> think.
> Thanks,
> -Vikas
>
> --- "Xie, Feng" <Feng.XieMARCONI.COM> wrote:
> > Hi, Vikas:
> >
> > Usually, only prefixes instead of nodes show in
> > the routing table. In the
> > case you described, the prefixes could be the ip
> > addresses of router
> > interfaces or the subnts the router interfaces
> > belong to. Packets are
> > delivered to interfaces instead of router ids.
> > The route type in the routing table could be
> > unicast or multicast instead
> > of ABR, ASBR and Transit Network.
> >
> > Feng Xie
> >
> > -----Original Message-----
> > From: Vikas B. Wadhwani [mailto:wvikasYAHOO.COM]
> > Sent: Monday, July 16, 2001 8:39 PM
> > To: OSPFDISCUSS.MICROSOFT.COM
> > Subject: Topology Info
> >
> >
> > Hi all,
> > I had a question about a particular topology.
> > I want to create a network with a bunch of routers,
> > say 50.I want to configure the whole network as ONE
> > and only ONE area.In addition to forwarding packets,
> > the routers are also a source and sink for
> > packets.They are connected in the form of a
> > semi-mesh
> > network by point to point links.
> > Since there is only one area, there are no ABRs and
> > ASBRs.
> > When the routing table is being created, what is the
> > TYPE of the nodes? In the routing table we need to
> > mention the Destination Type.The options available
> > are
> > ABR,ASBR and Transit Network.Now the routers are
> > neither ABR nor ASBR. They are also not transit
> > networks becasue they are not connected to any
> > network. How should each node be configured and what
> > will the routing table entries look like?
> > Thanks,
> > -Vikas
> >
> > =====
> >
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