From: Rick Burts (burts@xxxxxxxxxxxxxx)
Date: Fri Aug 17 2001 - 12:33:49 GMT-3
Demand Circuit is not a different network type, it is an option to treat
a particular network type: point to point (and virutal link).
I think part of the difficulty in this discussion is that the question
is perceived as either/or (it is either point to point or it is virtual
link). The reality is that it is both. A virtual link is treated as a
point to point (see the state in the show virtual link display below)
and is treated as a demand circuit (see the second and third lines of
the show virtual link display below).
Rick
Rick Burts, CCSI CCIE 4615 burts@mentortech.com
Mentor Technologies 240-568-6500 ext 6652
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On Fri, 17 Aug 2001 jonatale@earthlink.net wrote:
> i think demand circuit is a diff net type than p2p and than virtLink, demand
> ckts came out in a later rfc
> need to check the ospf database router LSA - should show the net type, or fin
d
> the rfc
> (kind of a guess)
>
> John.K.Feuerherd@WellsFargo.COM wrote:
>
> > Sanjay,
> > An OSPF Virtual link is considered a point-to-point circuit but it
> > is run as a demand circuit. This means that once the adjacency is
> > established the OSPF hellos and LSA refresh functions are suppressed. I
> > guess OSPF treats Virtual links as a bandwidth sensitive link.....
> >
> > You can see this happen if you set it up in a lab and before you do the
> > "area X virtual-link x.x.x.x" command do a "debug OSPF adj" and you will se
e
> > the hellos suppressed after the link reaches a FULL state.
> >
> > Thanks,
> > JF
> >
> > -----Original Message-----
> > From: Chuck Larrieu [mailto:chuck@cl.cncdsl.com]
> > Sent: Thursday, August 16, 2001 6:57 PM
> > To: sanjay; ccielab@groupstudy.com
> > Subject: RE: OSPF Virtual Link question
> >
> > I'll let you look up RFC 1793 and report back to us what you discover. ;->
> >
> > Good Reading!
> >
> > Chuck
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > sanjay
> > Sent: Thursday, August 16, 2001 5:31 PM
> > To: Chuck Larrieu; ccielab@groupstudy.com
> > Subject: Re: OSPF Virtual Link question
> >
> > Look at the info on the bottom. I have 2 routers connected back to back via
> > serial inter. R1 has an interface in Area 0 and the serial interface in Are
a
> > 2. On R2 a loopback interface is in Area 4 and the serial link is in Area 2
.
> > I have configured the Loopback interface with "ip ospf network
> > point-to-point" .
> >
> > r3#sh ip ospf virtual-links
> >
> > Virtual Link OSPF_VL0 to router 170.100.4.1 is up
> > Run as demand circuit
> > DoNotAge LSA allowed.
> > Transit area 2, via interface Serial2/0:1, Cost of using 74
> > Transmit Delay is 1 sec, State POINT_TO_POINT,
> > Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
> > Hello due in 00:00:07
> > Adjacency State FULL (Hello suppressed)
> >
> > r3#
> >
> > ----- Original Message -----
> > From: "Chuck Larrieu" <chuck@cl.cncdsl.com>
> > To: "sanjay" <ccienxtyear@hotmail.com>; <ccielab@groupstudy.com>
> > Sent: Thursday, August 16, 2001 4:56 PM
> > Subject: RE: OSPF Virtual Link question
> >
> > > it operates as a point to point link. why? because the RFC says so. :->
> > >
> > > from RFC 2328:
> > >
> > > The virtual link is treated as if it were an unnumbered point-to-
> > > point network belonging to the backbone and joining the two area
> > > border routers. An attempt is made to establish an adjacency over
> > > the virtual link. When this adjacency is established, the virtual
> > > link will be included in backbone router-LSAs, and OSPF packets
> > > pertaining to the backbone area will flow over the adjacency. Such
> > > an adjacency has been referred to in this document as a "virtual
> > > adjacency".
> > >
> > > the cost of the link is the sum of the costs of the links across the
> > transit
> > > area.
> > > for the real low down check out ftp://ftp.isi.edu/in-notes/rfc2328.txt
> > >
> > > HTH
> > >
> > > Chuck
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > > sanjay
> > > Sent: Thursday, August 16, 2001 4:41 PM
> > > To: ccielab@groupstudy.com
> > > Subject: OSPF Virtual Link question
> > >
> > >
> > > Does the virtual link run as a demand circuit and why ?
> > >
> > > -sanjay
> > > **Please read:http://www.groupstudy.com/list/posting.html
> > > **Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
> **Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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