RSVP-based MPLS without IGP

[hanuman]

Hi experts,

it is possible to use RSVP-signaled MPLS core without enabling any IGP-protocol, is it?

Juniper routers - M-series.

BR,

Petr

[darkiesan]

Hello,

An IGP is needed to secure connectivity between loopbacks over multiple hop connections. Loopbacks are used for ingress and egress for RSVP LSPs. Besides if you use RSVP and want traffic engineering, traffic engineering database need to be calculated by an IGP.

So in short I woudl say "No", you need an IGP.

Cheers

Patrik

[hanuman]

Thanks, Patrik, for your answer.

The matter concerns the state of mpls and not TE:

once I enable on the both ends RSVP and MPLS having only routes known from protocol "Direct", - will MPLS state come up?

What will show the output "show mpls lsp"?

BR,

Petr

[darkiesan]

LSP will be down since ingress router dont have a known route to the egress routers loopback.

Patrik

[hanuman]

Sorry, Patrik,

will be LSPs down even though RSVP and MPLS are on loopbacks enabled?

Are you sure, that RSVP does not carry information about the loopbacks?

BR,

Petr

[darkiesan]

Yes. RSVP and MPLS are not IGPs. RSVP calculates a label per hop going backwards from egress router to ingress router. But on each hop the needs to take best hop  towards ingress router loopback. So an IGP route is needed on each hop to point towards the loopback.

And just to be sure I tried this in my lab aswell. I had two routers directly attached to eachother using loopbacks and ISIS, RSVP, MPLS and BGP. To be extra fun, I added a L2VPN circuit and a L3VPN aswell. WHen ISIS was deactivated on one of the routers, RSVP LSPs was torned down after about a minute due to timeouts.

So Yes, the network need an IGP to support RSVP/MPLS based LSPs aswell.

Thanks!

Patrik

[mikep]

Hi,

IMHO you can establish RSVP tunnel without having IGP protocol by using static routes and ERO (ERO constraints + no-cspf; strict hop does not allow for IGP recursive lookup).  However, you would not be able to use any TED-based features (e.g. FFR, link coloring etc).

Kind Regards

Michael Pergament

[darkiesan]

Hi Mike!

I will check this in my lab aswell, since my test with TED features tore down the LSPs...

Patrik

[darkiesan]

Hi,

Tested your theory. Used static routes for connectivity between loopbacks. USed consgtraint path and turned of cspf. Still the LSP was tored down when ISIS was deactivated.

So it seems you are dependent on IGP.

Patrik

[darkiesan]

Sorry, I was to quick.

With a little patient the LSP came up!

So if you make sure there are static routes to accomodate connectivity for loopbacks, go cspf and ERO, you can get RSVP tunnels.

But in a more complex non lab network it doesnt seem like a good solution since you need to maintainm a static route table giving connectivity to all PE:s loopbacks.

Cheers

Patrik