From: Shamin (ccie.xpert@gmail.com)
Date: Wed Aug 22 2007 - 12:48:15 ART
Thanks Scott & Narbik,
I knew what the commands did individually. But the problem was, where to
apply . I guess I got it
clarified from you guys. Thank you very much for your time and inputs
Regards
Shamin
On 8/22/07, Narbik Kocharians <narbikk@gmail.com> wrote:
>
> The "OSPF Flooding Reduction" and the "demand circuit" works by reducing
> unnecessary refreshing and flooding of already known and unchanged
> information with a difference:
>
> In OSPF demand circuit, hellos and the flooding of the LSAs are
> suppressed, whereas, in flood reduction, the flooding of the LSAs are
> suppressed only and NOT the hellos.
>
>
>
> If you forget CCIE lab exam for a minute you will see that in real world
> implementation, when it comes to dialup networks, you would want to suppress
> the unnecessary refreshing AND the hellos, because you don't want either one
> of them to bring up the link. But in dedicated connections you don't really
> care about the hellos as much but you do not want the refreshing to occur
> every 30 minutes. Therefore, for dialup connection you use demand circuit
> and dedicated connections you would use flood reduction.
>
> But in CCIE everything goes, because they are testing you based on your
> experience and understanding, since we don't have a dialup connection in the
> CCIE exam, how would they test to see if you know what you are talking
> about? This is why you may see these used on dedicated circuits as well.
>
>
> On 8/22/07, Scott Morris <smorris@ipexpert.com> wrote:
>
> > Flood reduction on a demand circuit would be redundant. That's one of
> > the
> > features of demand circuit. (RFC 1793 if you're bored)
> >
> > Demand circuit is also used for hello suppression between two neighbors,
> > to
> > make things quieter.
> >
> > So both methods reduce the overall traffic flow on a link, just approach
> > it
> > differently based on the link-type. Knowing the details of both should
> > help
> > you make the correct decision if faced with it in the lab!
> >
> > HTH,
> >
> >
> > Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> > JNCIE
> > #153, CISSP, et al.
> > CCSI/JNCI-M/JNCI-J
> > VP - Technical Training - IPexpert, Inc.
> > IPexpert Sr. Technical Instructor
> >
> > A Cisco Learning Partner - We Accept Learning Credits!
> >
> > smorris@ipexpert.com
> >
> > Telephone: +1.810.326.1444
> > Fax: +1.810.454.0130
> > http://www.ipexpert.com
> >
> >
> > _____
> >
> > From: Shamin [mailto:ccie.xpert@gmail.com]
> > Sent: Wednesday, August 22, 2007 10:14 AM
> > To: smorris@ipexpert.com
> > Cc: subodh.rawat@wipro.com; reto_ccie@yahoo.com; ccielab@groupstudy.com
> > Subject: Re: IP ospf demand-circuit V/S IP ospf flood reduction ???
> >
> >
> > Scott,
> >
> > Thank you for your clarification.
> >
> > If you can clarify my original concern ,i will be grateful i.e when to
> > use
> > " ip ospf demand-circuit " v/s " ip ospf flood reduction".
> > I know that, demand-circuit is used over p-t-p networks. But is the
> > functionality of the two commands the same when it comes
> > to reducing the LSA refresh. Furthermore, can " ip ospf flood reduction
> > command " be used on a demand circuit,
> >
> > Thanks in advance
> >
> > Regards
> > Shamin
> >
> >
> > On 8/22/07, Scott Morris < smorris@ipexpert.com> wrote:
> >
> > Per Appendix B of RFC 2328:
> >
> > "LSRefreshTime
> > The maximum time between distinct originations of any particular
> > LSA. If the LS age field of one of the router's self-originated
> > LSAs reaches the value LSRefreshTime, a new instance of the LSA
> > is originated, even though the contents of the LSA (apart from
> > the LSA header) will be the same. The value of LSRefreshTime is
> > set to 30 minutes."
> >
> > "MaxAge
> > The maximum age that an LSA can attain. When an LSA's LS age
> > field reaches MaxAge, it is reflooded in an attempt to flush the
> > LSA from the routing domain (See Section 14). LSAs of age MaxAge
> > are not used in the routing table calculation. The value of
> > MaxAge is set to 1 hour."
> >
> > The re-flooding occurs at half of maxage (30 minutes).
> >
> > HTH,
> >
> >
> > Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> > JNCIE
> > #153, CISSP, et al.
> > CCSI/JNCI-M/JNCI-J
> > VP - Technical Training - IPexpert, Inc.
> > IPexpert Sr. Technical Instructor
> >
> > A Cisco Learning Partner - We Accept Learning Credits!
> >
> > smorris@ipexpert.com <mailto:smorris@ipexpert.com>
> >
> > Telephone: +1.810.326.1444
> > Fax: +1.810.454.0130
> > http://www.ipexpert.com
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com <mailto:nobody@groupstudy.com>
> > [mailto: nobody@groupstudy.com] On Behalf Of
> > subodh.rawat@wipro.com
> > Sent: Wednesday, August 22, 2007 4:39 AM
> > To: reto_ccie@yahoo.com ; ccie.xpert@gmail.com; ccielab@groupstudy.com
> > Subject: RE: IP ospf demand-circuit V/S IP ospf flood reduction ???
> >
> > Just to correct you: This refreshment of LSA takes place after 1 hour
> > not 30
> > minutes.
> >
> > Subodh
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto: nobody@groupstudy.com] On Behalf Of
> >
> > eicc
> > tester
> > Sent: Wednesday, August 22, 2007 4:38 AM
> > To: Shamin; Cisco certification
> > Subject: Re: IP ospf demand-circuit V/S IP ospf flood reduction ???
> >
> > Hi
> >
> > "ip ospf flood reduction" just avoid the refreshement of LSA every 30
> > minutes.
> >
> > "ip ospf demand circuit" mean that a link which is under an OSPF area ,
> > don,t send OSPF hello packet all the time. This avoid the fact of bring
> > the
> > circuit (probaly and dial or isdn) just for sent hello packet
> > periodically,
> > the neigbhor relations is still maintaned.
> >
> >
> > Shamin <ccie.xpert@gmail.com> wrote:
> > Hi All,
> >
> > Can any one tell me , when the commands "ip ospf flood reduction" is
> > used
> > over " ip ospf demand circuit" .
> > I know that, "Ip ospf demand circuit is used in point to point
> > connections.
> > Does that mean, ip ospf flood reduction"
> > is used in Broadcast and NBMA OSPF networks. I am bit confused as to
> > which
> > command to apply in a particular scenario, mainly if the question asks
> > to
> > reduce the "paranoid updates" in ospf that occurs every 30mins.
> >
> > Thanks in advance.
> >
> > Regards
> > Shamin
> >
> > _______________________________________________________________________
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>
> --
> Narbik Kocharians
> CCIE# 12410 (R&S, SP, Security)
> CCSI# 30832
> www.Net-WorkBooks.com
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