From: John.K.Feuerherd@xxxxxxxxxxxxxx
Date: Fri Aug 17 2001 - 00:19:48 GMT-3
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 see
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 Area
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
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