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Re: [OSPF] ospf backbone area
>
> Hi Sinbad,
> See inline.
>
> On Oct 6, 2009, at 6:20 AM, Sinbad wrote:
>
> > ...........................
> > . + .
> > . | 3+---+ . N12 N14
> > . N1|--|RT1|\ 1 . \ N13 /
> > . | +---+ \ . 8\ |8/8
> > . + \ ____ . \|/
> > . / \ 1+---+8 8+---+6
> > . * N3 *---|RT4|------|RT5|--------+
> > . \____/ +---+ +---+ |
> > . + / \ . |7 |
> > . | 3+---+ / \ . | |
> > . N2|--|RT2|/1 1\ . |6 |
> > . | +---+ +---+8 6+---+ |
> > . + |RT3|------|RT6| |
> > . +---+ +---+ |
> > . 2/ . Ia|7 |
> > . / . | |
> > . +---------+ . | |
> > .Area 1 N4 . | |
> > ........................... | |
> > .......................... | |
> > . N11 . | |
> > . +---------+ . | |
> > . | . | | N12
> > . |3 . Ib|5 |6 2/
> > . +---+ . +----+ +---+/
> > . |RT9| . .........|RT10|.....|RT7|---
> > N15.
> > . +---+ . . +----+ +---+
> > 9 .
> > . |1 . . + /3 1\ |
> > 1 .
> > . _|__ . . | / \ __|
> > _ .
> > . / \ 1+----+2 |/ \ /
> > \ .
> > . * N9 *------|RT11|----| * N6
> > * .
> > . \____/ +----+ |
> > \____/ .
> > . | . . |
> > | .
> > . |1 . . + |
> > 1 .
> > . +--+ 10+----+ . . N8 +---
> > + .
> > . |H1|-----|RT12| . . |
> > RT8| .
> > . +--+SLIP +----+ . . +---
> > + .
> > . |2 . . |
> > 4 .
> > . | . .
> > | .
> > . +---------+ . . +--------
> > + .
> > . N10 . .
> > N7 .
> > . . .Area
> > 2 .
> > .Area
> > 3 . ................................
> > ..........................
> >
> >
> >
> > 1) In the above ospf topology according to ospf rfc 2328 in section
> > 3.4, it states that
> >
> > "Note that a failure of the line between Routers RT6 and RT10
> > will cause the backbone to become disconnected."
> >
> > Though there is router RT7 in area 2 still connected to the
> > backbone.It confused my understanding of
> > disconnected backbone area. Can someone shed some light on this.
>
> I believe this issue has been raised before although I couldn't find
> an errata. The figure is incorrect. Network N8 should be in the
> backbone area rather than Area 2.
>
>
> >
> >
> > 2) why should routers connected by a point to point link having
> > interface addresses assigned,
> > should advertise a stub link a stub connection to the other
> > router's interface address.
>
> This dates back to the fact that P2P links were represented as a host
> route to the destination network on BSD based systems. Those of you
> who are familiar with GateD will remember this. Note that there is
> also an option to represent/advertise P2P links as a subnets. Most if
> not all routers vendors advertise the subnet.
Do you have a choice here? I read the RFC that if the P2P link has
a host route (mask = 255.255.255.255) you have to advertise a stub
link to the other router's interface address.
>
> Hope this helps,
> Acee