From: William Chen (kwchen@netvigator.com)
Date: Mon Jan 19 2004 - 08:32:59 GMT-3
Hi,
Great idea on making the ISDN an stub no summary area, so that ISDN will
not flap when there is a topology changes of other networks. However, if the
ISDN is used to backup the frame-relay (which is an area 0 of OSPF), a down
of the frame relay may cause a partition of backbone area of OSPF. To fix
it, we can create a virtual link across the ISDN to connect the backbone
area when frame realy is down. If we configure the ISDN as stub no-summary
area, virtual-link cannot to create. Do yours guys have any comment on this
scenario.
Best Regards,
William Chen
----- Original Message -----
From: "Arvind Yadav" <arvindyadav@comcast.net>
To: "Nancy Khln" <nancy_merill@yahoo.com>; <ccielab@groupstudy.com>
Sent: Monday, January 19, 2004 3:04 PM
Subject: Re: OSPF demand!
> I think demand ckt doesn't trigger the ISDN at all it only suppress the
ospf
> hello packet so that ISDN will not trigger because on hello packet. To
> trigger the ISDN you need to specify the interesting traffic by using the
> dialer list. That it my understanding
>
> In this case ISDN gets triggered because whenever any FR link goes down,
it
> means there is change in topology OSPF flood LSA accors ISDN link which
> makes the ISDN link up.
>
> You requirement would have meet very easily by using the dialer-watch. Try
> to put RA BRI and RB BRI and RC serial0 in OSPF stub no summary area. I
> think in that case ISDN will only triggred when FR link b/w RA and RC
fails.
>
> Arvind
>
>
>
> ----- Original Message -----
> From: "Nancy Khln" <nancy_merill@yahoo.com>
> To: <ccielab@groupstudy.com>
> Sent: Sunday, January 18, 2004 8:09 PM
> Subject: OSPF demand!
>
>
> > Hi,
> >
> > I have three Cisco 2500 routers using the network setup in the diagram
> below:
> >
> > RoA-------ISDN-----RoB
> > | /
> > | S1
> > | /
> > | /
> > | /
> > Frame relay /
> > | /
> > | /
> > | /
> > Se1 /
> > | S0
> > RouterC/
> >
> > Requirement: I need to configure ISDN as a back up for the Frame Relay.
> > Cannot use static, backup and dialer watch in the ISDN section. All ip
> addreses involved in this scenario must be reachable.
> > OSPF is running over the frame relay connection between Ra/Rc, Rc/Rb
the
> Frame connection and across the ISDN link Ra/Rb.
> > , 2 parallel path exists between Ra and Rb, by configuring OSPF demand
> circuit
> > on the ISDN link and making sure that the ISDN link has a higher cost
OSPF
> path between the 2 routers, I am using the ISDN link only when
> > a prefix cannot be reached over the Frame Relay link. When the Frame
relay
> link between Ra/Rc, or Rc/Rb goes down, OSPF demand circuit kicks in and
> > the ISDN link comes up.
> > So far so good, everything is working. What if I want to bring up the
ISDN
> link only when the frame relay link between
> > Ra and Rc is down, same requirements but I want to monitor only one
frame
> relay link. Now the OSPF demand feature doesn help.
> > What do I need to do to implement this?
> > Thank you
> > Nancy
> >
> >
> >
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