Hi ,
New to networks, maybe some answers to this question?

In the following scenario
12.13.14.0 network
|
RTR A======ISDN backup dial line RIP==========RTR B
|| ||
RIP OSPF
|| ||
===RTR C==OSPF==RTR C==OSPF=RTR D===OSPF===RTR E


The connection between router's A and B is down unless RTR A to RTR C
is broken, down otherwise.

In this scenario, router A is advertising the 12.13.14.0 network with a
better cost to rotuer B at a higher cost than to router C. All the
routers in the OSPF domain are in one area 0.0.0.2.

In this scenario, if the A to C link is broken and then fixed but the A
to B link remains up, should we expect the routing tables to go back to
taking the better cost path? Updates should come from RTR C via RTR A
I would beleive. I think some of the Cisco web sites indicate it
should but is this correct to assume?

Kim

test...@gmail.com wrote:
> Hi ,
> New to networks, maybe some answers to this question?
>
> In the following scenario
> 12.13.14.0 network
> |
> RTR A======ISDN backup dial line RIP==========RTR B
> || ||
> RIP OSPF
> || ||
> ===RTR C==OSPF==RTR C==OSPF=RTR D===OSPF===RTR E
>
>
> The connection between router's A and B is down unless RTR A to RTR C
> is broken, down otherwise.
>
> In this scenario, router A is advertising the 12.13.14.0 network with a
> better cost to rotuer B at a higher cost than to router C. All the
> routers in the OSPF domain are in one area 0.0.0.2.
>
> In this scenario, if the A to C link is broken and then fixed but the A
> to B link remains up, should we expect the routing tables to go back to
> taking the better cost path? Updates should come from RTR C via RTR A
> I would beleive. I think some of the Cisco web sites indicate it
> should but is this correct to assume?
>
> Kim

The map is off. The OSPF link is between router B and E.

<testcpp@gmail.com> wrote:
>
> test...@gmail.com wrote:
>> Hi ,
>> New to networks, maybe some answers to this question?
>>
>> In the following scenario
>> 12.13.14.0 network
>> |
>> RTR A======ISDN backup dial line RIP==========RTR B
>> || ||
>> RIP OSPF
>> || ||
>> ===RTR C==OSPF==RTR C==OSPF=RTR D===OSPF===RTR E
>>
>>
>> The connection between router's A and B is down unless RTR A to RTR C
>> is broken, down otherwise.
>>
>> In this scenario, router A is advertising the 12.13.14.0 network with
>> a
>> better cost to rotuer B at a higher cost than to router C. All the
>> routers in the OSPF domain are in one area 0.0.0.2.
>>
>> In this scenario, if the A to C link is broken and then fixed but the
>> A
>> to B link remains up, should we expect the routing tables to go back
>> to
>> taking the better cost path? Updates should come from RTR C via RTR
>> A
>> I would beleive. I think some of the Cisco web sites indicate it
>> should but is this correct to assume?
>>
>> Kim
>
> The map is off. The OSPF link is between router B and E.

Sounds like a homework problem, and like someone was in a rush to get it
on the usenet besides.

I didn't quite understand whether the ISDN path costs more or less than
the A to C path. Also, you have two routers named C. "Better cost at a
higher cost" is very confusing to me.

In general, the lower cost paths will always be used, either with RIP or
with OSPF. And the only ambiguity would exist for equal-cost paths,
where OSPF will allow any equal cost paths between two routers to be
used simultaneously.

So I think the answer depends on which two routers you're talking about,
as the two end points of the comm session.

For example, if the ISDN link remains up, depending on how the costs are
assigned, it would be possible for comms from the left-most C to B to
always go through A and the ISDN link, but comms from that second C you
show and B to take both the ISDN path and the path through E.

Bert

<testcpp@gmail.com> wrote in message
news:1161195700.691470.47340@i3g2000cwc.googlegrou ps.com...
>
> test...@gmail.com wrote:
> > Hi ,
> > New to networks, maybe some answers to this question?
> >
> > In the following scenario
> > 12.13.14.0 network
> > |
> > RTR A======ISDN backup dial line RIP==========RTR B
> > || ||
> > RIP OSPF
> > || ||
> > ===RTR C==OSPF==RTR C==OSPF=RTR D===OSPF===RTR E
> >
> >
> > The connection between router's A and B is down unless RTR A to RTR C
> > is broken, down otherwise.
> >
> > In this scenario, router A is advertising the 12.13.14.0 network with a
> > better cost to rotuer B at a higher cost than to router C. All the
> > routers in the OSPF domain are in one area 0.0.0.2.
> >
> > In this scenario, if the A to C link is broken and then fixed but the A
> > to B link remains up, should we expect the routing tables to go back to
> > taking the better cost path? Updates should come from RTR C via RTR A
> > I would beleive. I think some of the Cisco web sites indicate it
> > should but is this correct to assume?

the Q may be about routing protocol behaviour rather than backup.

You dont have OSPF thru out so topology is going to depend on the RIP / OSPF
interactions.

Finally how / whether the ISDN line goes down after being active depends on
setup.

If it is dial on demand rather than actual Cisco "backup" link type then the
RIP advertisement packets can keep the line up. "backup" can mean lots of
things, so you need to check exactly what you have before you can sort out
the answer.
> >
> > Kim
>
> The map is off. The OSPF link is between router B and E.
>
--
Regards

stephen_hope@xyzworld.com - replace xyz with ntl

stephen wrote:
> <testcpp@gmail.com> wrote in message
> news:1161195700.691470.47340@i3g2000cwc.googlegrou ps.com...
> >
> > test...@gmail.com wrote:
> > > Hi ,
> > > New to networks, maybe some answers to this question?
> > >
> > > In the following scenario
> > > 12.13.14.0 network
> > > |
> > > RTR A======ISDN backup dial line RIP==========RTR B
> > > || ||
> > > RIP OSPF
> > > || ||
> > > ===RTR C==OSPF==RTR C==OSPF=RTR D===OSPF===RTR E
> > >
> > >
> > > The connection between router's A and B is down unless RTR A to RTR C
> > > is broken, down otherwise.
> > >
> > > In this scenario, router A is advertising the 12.13.14.0 network with a
> > > better cost to rotuer B at a higher cost than to router C. All the
> > > routers in the OSPF domain are in one area 0.0.0.2.
> > >
> > > In this scenario, if the A to C link is broken and then fixed but the A
> > > to B link remains up, should we expect the routing tables to go back to
> > > taking the better cost path? Updates should come from RTR C via RTR A
> > > I would beleive. I think some of the Cisco web sites indicate it
> > > should but is this correct to assume?
>
> the Q may be about routing protocol behaviour rather than backup.
>
> You dont have OSPF thru out so topology is going to depend on the RIP / OSPF
> interactions.
>
> Finally how / whether the ISDN line goes down after being active depends on
> setup.
>
> If it is dial on demand rather than actual Cisco "backup" link type then the
> RIP advertisement packets can keep the line up. "backup" can mean lots of
> things, so you need to check exactly what you have before you can sort out
> the answer.
> > >
> > > Kim
> >
> > The map is off. The OSPF link is between router B and E.
> >
> --
> Regards
>
> stephen_hope@xyzworld.com - replace xyz with ntl

Thank you for the replies. It is not homework, I work as a database
administrator for our business and our network administrator is out
this week so I've been asked to cover and I'm out of my area of
expertise. There is two router Cs my mistake in not proofing.

It's a matter of RIP and how OSPF engage I think. There's a code
problem with the router A and that is keeping the backup line active
so we can workaround that, it's just that we had all our traffic going
on what we thought would be a worst path.

Thanks again.