[c-nsp] forced path MPLS tunnel question

[Chris Mason]

Apologies if I misinterpreted your question, but ....

For MPLS/TE you need an IGP of ISIS or OSPF in conjunction with RSVP
within the network.

The requirement on ISIS or OSPF is because it requires a link state
protocol with visibility of the entire network (EIGRP doesn't cut it).
When you enable RSVP and TE on an interface, certain characteristics
of the interface are included within ISIS LSP (e.g. bandwidth being
the simplest).

When you create a tunnel on a head end router it will use something
called CSPF (Constrained Shortest Path First) to find a path through
your network which matches the constraints you have defined on the
logical tunnel interface (i.e. minimum bandwidth of 100k) - it uses
the extra information in the LSP to work this out. When it has
computed a viable path, it uses RSVP to signal the tunnel using Path
messages.

After all that has happened the tunnel will hopefully come up and then
you need to use static routing or a feature called AutoRoute Announce
or Forwarding Adjacency to actually get traffic to enter the tunnel.

Basically, you need OSPF or ISIS with RSVP and MPLS TE enabled on
every interface you want the tunnel to traverse.

/Chris

On 17 January 2012 15:27, Gert Doering <gert at greenie.muc.de> wrote:
> Hi,
>
> On Tue, Jan 17, 2012 at 09:06:02AM -0600, Cory Ayers wrote:
>> > the explicit-path configured lists the loopback interfaces of all the
>> > routers I want the tunnel to touch, in sequence, with no gaps.  Labels
>> > for
>> > the loopbacks are there, as for the endpoint:
>>
>> Have you tried using the point-to-point next-hop (as it would appear in a traceroute) rather than loopbacks for each hop?
>>
>> ip explicit-path name FOO
>>   next-address (P2P hop 1)
>
> Haven't tried that, as we don't distribute labels for non-Loopback20
> addresses (all our normal traffic runs untagged, only EoMPLS between
> specific Loopbacks and L3 VPNs with iBGP between Loopback20 has labels).
>
> But indeed.  That definitely *changes* the error messages I get :-) and
> I think now I'm missing "more interfaces with RSVP on".
>
> Thanks for the hint.  I had never considered using non-labeled next-hop
> addresses...
>
>
> [..]
>> You'll still need mpls and traffic-eng tunnels configured on each
>> interface of the label path.  You can verify with show mpls interfaces.
>
> Yeah, figured that one out, that "mpls traffic-eng tun" is needed on
> all MPLS-enabled interfaces (... that would carry this tunnel).  Need
> to test that next, with a shorter path, don't want to touch all the
> production network right now.
>
>> And then there's the IGP.
>
> Uh, what exactly?
>
> gert
>
> --
> USENET is *not* the non-clickable part of WWW!
>                                                           //www.muc.de/~gert/
> Gert Doering - Munich, Germany                             gert at greenie.muc.de
> fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
>
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