From: Chris Fontes (cfontes@atrion.net)
Date: Thu Mar 25 2004 - 14:23:52 GMT-3
Absolutely
-----Original Message-----
From: Packet Man [mailto:ccie2b@hotmail.com]
Sent: Thursday, March 25, 2004 12:05 PM
To: alexander.arsenyev@ericsson.com; ccielab@groupstudy.com
Subject: RE: OSPF Demand circuit and Backup
Thanks everyone for speaking up about this.
Alex, correct me if I'm wrong on this, but if, dialer-list permits all ip
traffic, that would cover OSPF routing traffic as well, would it not?
And, because of OSPF demand-circuit, Hello's and lsa's would still be
suppressed.
And, so getting back to the original question, you agree that if ospf
demand-circuit is configured over an ISDN link, there's no need to configure
another backup method. The ISDN link will be the backup method if it's
configured as an OSPF demand circuit.
Furthermore, because the primary link can and should be configured with a
lower cost than the ISDN link, OSPF will always send user traffic over the
primary link as long as it's up. Would you agree?
Thanks again, pm
>From: "Alexander Arsenyev (GU/ETL)" <alexander.arsenyev@ericsson.com>
>Reply-To: "Alexander Arsenyev (GU/ETL)" <alexander.arsenyev@ericsson.com>
>To: "'ccielab@groupstudy.com'" <ccielab@groupstudy.com>
>Subject: RE: OSPF Demand circuit and Backup
>Date: Thu, 25 Mar 2004 17:35:51 +0100
>
>One small but important correction - "ospf will converge and routing will
>take place over the link" only if OSPF is defined as interesting traffic.
>So reachability with OSPF demand-cuirciut is not automatic, You have to
>make
>sure that IP protocol 89 (OSPF) is covered by dialer-list statement.
>HTH,
>Cheers
>Alex
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
>Chris Fontes
>Sent: 25 March 2004 16:20
>To: 'Joseph D. Phillips'; Group Study (E-mail)
>Subject: RE: OSPF Demand circuit and Backup
>
>
>Hi all
>
>Not sure I agree with your whole explanation Joseph.
>
>OSPF demand circuit does keep the link from flapping, but once there is a
>topology change the link will come up, ospf will converge and routing will
>take place over the link. It will provide reachability.
>
>With dialer watch you only need a dialer map statement for the specific
>network(s) that are being watched with the dialer watch-list not for each
>network that would be lost if the primary connection goes down (ie if your
>learning 6 routes over your primary link, you could just watch one of them
>with dialer watch). If the network drops from the routing table, dialer
>watch will bring the ISDN link up, ospf will converge and routing will take
>place over the link.
>
>Each method would provide the same results.
>
>Packet Man I can't think of any reason why you would cofigure both at the
>same time. Its two different methods that provide the same results.
>
>Chris
>
>-----Original Message-----
>From: Joseph D. Phillips [mailto:jphillips@ufcwdrugtrust.org]
>Sent: Thursday, March 25, 2004 10:44 AM
>To: Group Study (E-mail)
>Subject: OSPF Demand circuit and Backup
>
>
>Dialer watch and OSPF demand-circuit accomplish two different purposes.
>
>OSPF demand only keeps the BRI link from flapping after the BRI's IP
>network
>is defined under the OSPF router process.
>
>By itself, it does not provide any reachability to any networks.
>
>If you want a true backup of a frame-relay network, you'd need
>dialer-watch,
>and you'd have to create a dialer map statement for each network which
>would
>be lost if the primary connection goes down.
>
>
>-----Original Message-----
>From: Packet Man [mailto:ccie2b@hotmail.com]
>Sent: Thursday, March 25, 2004 07:12
>To: ccielab@groupstudy.com
>Subject: OSPF Demand circuit and Backup
>
>
>Hi all,
>
>When an ISDN circuit is configured as an OSPF demand-circuit to backup
>another OSPF link in the same area, should and can any other backup method
>such as Dialer Watch also be configured on the same ISDN link?
>
>My sense is that there's no need to configure any other backup method and
>doing so would only complicate things and lead to unexpected results.
>
>Here's what I believes happens in such a situation (without 2nd method
>configured).
>
>Primary link goes down.
>
>This causes ospf to see a topology change has occurred.
>
>OSPF floods lsa over all links including ISDN circuit which brings up ISDN
>circuit.
>
>OSPF updates the route table to reflect new topology.
>
>Now, user traffic that would have used the primary link now uses the ISDN
>link.
>
>Is this simplified chain of events correct? Are there other significant
>things that occur that we should be aware of?
>
>Thanks in advance, pm
>
>_________________________________________________________________
>Get rid of annoying pop-up ads with the new MSN Toolbar FREE!
>http://toolbar.msn.com/go/onm00200414ave/direct/01/
>
>_______________________________________________________________________
>Please help support GroupStudy by purchasing your study materials from:
>http://shop.groupstudy.com
>
>Subscription information may be found at:
>http://www.groupstudy.com/list/CCIELab.html
>
>_______________________________________________________________________
>Please help support GroupStudy by purchasing your study materials from:
>http://shop.groupstudy.com
>
>Subscription information may be found at:
>http://www.groupstudy.com/list/CCIELab.html
>
>_______________________________________________________________________
>Please help support GroupStudy by purchasing your study materials from:
>http://shop.groupstudy.com
>
>Subscription information may be found at:
>http://www.groupstudy.com/list/CCIELab.html
>
>This communication is confidential and intended solely for the
>addressee(s). Any unauthorized review, use, disclosure or distribution is
>prohibited. If you believe this message has been sent to you in error,
>please notify the sender by replying to this transmission and delete the
>message without disclosing it. Thank you.
>
>E-mail including attachments is susceptible to data corruption,
>interruption, unauthorized amendment, tampering and viruses, and we only
>send and receive e-mails on the basis that we are not liable for any such
>corruption, interception, amendment, tampering or viruses or any
>consequences thereof.
>
>_______________________________________________________________________
>Please help support GroupStudy by purchasing your study materials from:
>http://shop.groupstudy.com
>
>Subscription information may be found at:
>http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Thu Apr 01 2004 - 08:15:47 GMT-3