[j-nsp] ospf virtual link and rsvp lsp

Wed Aug 11 19:48:17 EDT 2004

I think the text is messed up.  There's really no reason to use
an LSP for the virtual link.  Yes, the LSP means you can control
the path of the virtual link, but that doesn't make any difference
since when an area is a VL transit area, packets heading to the
backbone can use _any_ available path through the transit area;
packets do NOT have to follow the virtual link.

-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net
[mailto:juniper-nsp-bounces at puck.nether.net]On Behalf Of R Che
Sent: Wednesday, August 11, 2004 3:23 PM
To: Raymond Cheh; juniper-nsp at puck.nether.net
Subject: RE: [j-nsp] ospf virtual link and rsvp lsp

but the example on that page doesn't use rsvp lsp at all. is it missing on
the page or it's done automatically?

Raymond Cheh <rcheh at juniper.net> wrote:
Ah, I see where you got the page now. The one I quoted is in the OSPF
Overview and the
one here is in the OSPF Configuration Guideline section.

The short answer is no, you don't need rsvp lsp to set up the virtual-link
as long as
the end-points are reachable between the 2 routers.

Having an lsp allows you to control the path the virtual-link is set up
because
with the lsp between the 2 routers of the virtual-link endpoints, it
provides the
most direct path for the virtual-link to go through.

Hope this helps.

Raymond
-----Original Message-----
From: R Che [mailto:jlablab at yahoo.com]
Sent: Wednesday, August 11, 2004 10:40 AM
To: jlablab at yahoo.com; Raymond Cheh; juniper-nsp at puck.nether.net
Subject: RE: [j-nsp] ospf virtual link and rsvp lsp

This is the page copied from the pdf. Is virtual-link really done by using
rsvp lsp? I thought this is something related to setting v-bit (virtual-link
endpoint) on OSPF etc..

Configure an RSVP LSP

If any router on the backbone is not physically connected to the backbone
itself, you must

establish a virtual connection between that router and the backbone. You can
establish a

virtual connection between area border routers by configuring an RSVP LSP.

To configure an RSVP LSP for OSPF, include the virtual-link statement when
configuring the

backbone area (area 0):

[edit protocols ospf area 0.0.0.0]

virtual-link neighbor-id router-id transit-area area-id;

To configure an RSVP LSP for OSPFv3, include the virtual-link statement when
configuring the

backbone area (area 0):

[edit protocols ospf3 area 0.0.0.0]

virtual-link neighbor-id router-id transit-area area-id;

For a list of hierarchy levels at which you can configure this statement,
see the statement

summary section for this statement.

Specify the router ID (as an IPv4 address) of the router at the other end of
the LSP. This router

must be an area border router that is physically connected to the backbone.
Also, specify the

number of the area through which the LSP transits.

For the virtual connection to work, you also must configure a LSP to the
backbone area on

the remote area border router (the router at the other end of the LSP).

Example: Configure an RSVP LSP

Configure an RSVP LSP on the local router. This router must be an area
border router that is

physically connected to the backbone.

[edit protocols ospf]

area 0.0.0.0 {

virtual-link neighbor-id 192.168.0.3 transit-area 1.1.1.1;

interface t3-1/0/0 {

hello-interval 1;

dead-interval 3;

}

}

You must also configure an LSP on the remote area border router:

[edit protocols ospf]

area 0.0.0.0 {

virtual-link neighbor-id 192.168.0.5 transit-area 1.1.1.1;

}

R Che <jlablab at yahoo.com> wrote:
The guide is for JunOS 6.2. So I believe this must be corrected in latest
release?

Raymond Cheh wrote:Which JunOS release is this guide? I checked both 6.0 and
6.4 and I think
the passage to which you refer is this one:

Backbone Areas

An OSPF backbone area consists of all networks in area ID 0.0.0.0, their
attached routers, and all area border routers. The backbone itself does not
have any area border routers. The backbone distributes routing information b
etween areas. The backbone is simply another area, so the terminology and
rules of areas apply: a router that is directly connected to the backbone is
an internal router on the backbone, and the backbone's topology is hidden
from the other areas in the AS.

The routers that make up the backbone must be physically contiguous. If they
are not, you must configure virtual links to! create the appearance of
backbone connectivity. You can create virtual links between any two area
border routers that have an interface to a common nonbackbone area. OSPF
treats two routers joined by a virtual link as if they were connected to an
unnumbered point-to-point network.

** End of excerpt **

In this case, the virtual link is to connect the backbone area so that it
becomes one.

Please let me know if you have further questions. Thanks.

Raymond
rcheh at juniper.net

-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net on behalf of R Che
Sent: Tue 8/10/2004 4:41 PM
To: juniper-nsp at puck.nether.net
Subject: [j-nsp] ospf virtual link and rsvp lsp

On JunOS Routing Protocol Configuration Guid page 284, it says "you can
establish a virtual connection between area border routers by configuring an
RSVP LSP". In the rest of this page, it says about virtual link, and I can't
think of any relation between a RS! VP LSP and virtual link?

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