From: André Bersvendsen (an-bersv@xxxxxxxxx)
Date: Wed Apr 24 2002 - 16:32:51 GMT-3
Either alternative 1 or 2 is completely correct.
But alternative 2 is the most correct alternative.
My answer is:
The BRI or dialer interface is configured as normal regarding dialer
maps or dialer strings. Routing is handled by "ip ospf demand-circuit"
alone.
Do NOT deny OSPF in the access-list assigned to the dialer-group.
And some extra information:
Use "ip ospf demand-circuit" on only one end of the ISDN connection. In
an environment with a SOHO and a HQ use it only on the SOHO (It might
not work if you configure DC on both ends!).
The line will go up when the SOHO router (or HQ if a dialer exists in
this direction) is powered on. Then the DC bit is set in the OSPF
packages sent to the HQ router and then both sides will use OSPF DC
until one of them is reloaded. Then link must go up again to inform HQ
about DC.
Changes in the OSPF database will bring the line up to inform the other
end.
So DC will work best in stub, totally stub or nssa areas.
Do not run any other IP routing protocols on the BRI or dialer interface
at the same time. It make no sense and it might damage the effect of a
"silent link" when no user traffic is sent.
Flapping:
I have heard that it can be a problem with OSPF DC and PPP. And I have
not tested it in my LAB. So I hope anyone in the group might know
something about this.
The "problem" is that PPP send over the local IP address in the PPP
setup. The result is that the other ends IP address is treated as
connected when the link is up. When the link goes down this connected
route disappear from the interface and forces OSPF to take up the ISDN
link to inform the other end about this change. Then the connected route
is back again... And you have it going up and down.
Solution: (config-if)#no peer neighbor-route
Best Regards,
Andri Bersvendsen
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Babacar Diop
Sent: 24. april 2002 19:54
To: cciegroup
Subject: Ospf demand-circuit
Group,
Can anyone clarify this for me. Which is true, 1 or 2?
1)When doing ISDN backup wiht OSPF demand-circuit, do
you use it in conjunction with dialer-watch,
floating-static, backup interface or snapshot routing?
2)Do you use "ip ospf demand-circuit" only by itself
under the BRI. If so then you need then how do you
bring up the line since you have to deny ospf with an
access-list to keep it form bringing the line up.
Thanks for your input
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