From: OhioHondo (ohiohondo@columbus.rr.com)
Date: Thu Feb 06 2003 - 20:49:20 GMT-3
And adding on to David's comment -- since the OSPF neighbor relationship is
sitting dormant awaiting the failure of alternate paths with better OSPF
costs -- when it is time for the BRI circuit to be used I believe there is
little convergence time (for bringing up the backup OSPF link).
This somewhat immediate switch from the primary to the backup is the
advantage of the demand circuit. (a is preferred over b)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Voss, David
Sent: Thursday, February 06, 2003 6:25 PM
To: 'sam'; ccielab@groupstudy.com
Subject: RE: ISDN again - Preventing OSPF traffic from bringing up a
secon dary line
If you are running OSPF over a BRI in the same area that the serial
interface is in, I suggest you also do the following:
int bri 0
ip ospf cost 9999
When you enable ip ospf demand circuit, the bri will actually come up to
create the neighbor relationship over the bri. You will then see 2 entries
in your ospf neighbor table (sh ip ospf nei) for the adjacent router. The
bri nei relationship should stay up even when the bri is down.
-----Original Message-----
From: sam [mailto:sam@avtechusa.com]
Sent: Thursday, February 06, 2003 4:47 PM
To: ccielab@groupstudy.com
Subject: ISDN again - Preventing OSPF traffic from bringing up a
secondary line
Sorry for the lengthy post. got some doubts and wanted to clear 'em up.
QN: I got another one here...
BRI is configured as a backup for the serial link.
Let us say that I do not want to bring up my BRI interface which is
defined in the same OSPF area as my primary link.
____ ____
| |s0 -------------- s0| |
| r1 | | r2 |
| |bri0 ---------- bri0| |
~~~~ ~~~~
I can go into say R2's BRI0 and configure
(a) ip ospf demand-circuit
(b) deny ospf traffic to bri0 (seen below in excerpt from Doc. CD on
Dialer Watch)
access-list 101 remark Define Interesting Traffic
access-list 101 deny ospf any any
!Mark OSPF as uninteresting.
!This will prevent OSPF hellos from keeping the link up.
Access-list 101 permit ip any any
dialer-list 1 protocol ip list 101
!Interesting traffic is defined by access-list 101.
!This is applied to BRI0 using dialer-group 1.
Question: Do both actions provide the same results? The most obvious
scenario would be to use
Ip ospf demand-circuit, in my opinion. or even better, use
dialer watch or floating static.
But what are the implications then ? (a) or (b) ?
Am I correct to say that the dialer group command is used to define
interesting traffic. Denying OSPF traffic means that the ISDN connection
will not be brought up by OSPF hellos. Once the DDR has been activated
on the BRI interfaces, the dialer group's restrictions on OSPF traffic
WILL NOT apply to traffic flowing through the BRI link.
TIA
Sam Sena
.
.
.
This archive was generated by hypermail 2.1.4 : Sat Mar 01 2003 - 11:06:14 GMT-3