Mailing List Archive: RSVP-TE (MPLS-TE) and LDP question

RSVP-TE (MPLS-TE) and LDP question

May 11, 2020, 11:02 AM

Post #1 of 3 (628 views)

Seems that when I try to use RSVP in place of LDP for label distribution, I
cannot completely remove mpls ldp configs from IOS XR, but I can from IOS XE

On an RSVP-TE Tunnel headend, I have .

IOS XR (XRv9000)

mpls ldp

router-id 10.0.0.11

.and if I remove that with "no mpls ldp" I loose connectivity to the MPLS
L3VPN that is also on that PE

But.in IOS XE (csr1000v) I have.

mpls ldp router-id lo0 force

.and if I remove that with "no mpls ldp router-id Loopback0" (and also
remove "mpls ip" from the pe---p uplink) I am still good to the MPLS L3VPN
that is also on that PE

I don't understand what is going on with this minimal ldp config in IOS XR
that causes L3VPN to no longer work after I remove that small config shown
above.

As a side note, I can remove that ldp config from XR p core nodes.. Just not
XR pe nodes

.furthermore, I think since I have that ldp config in my PE's, I have LFIB
"Unlabelled" entries in my PE, I guess since I have no LDP config in the
transit P nodes. But in XE since I can remove that ldp config I no longer
have Unlabelled lfib entries and a nice clean lfib with only the L3vpn
aggregate label

-Aaron

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Re: RSVP-TE (MPLS-TE) and LDP question [ In reply to ]

james at towardex

May 11, 2020, 1:25 PM

Post #2 of 3 (627 views)

Permalink

On Mon, May 11, 2020 at 01:02:23PM -0500, Aaron Gould wrote:
> Seems that when I try to use RSVP in place of LDP for label distribution, I
> cannot completely remove mpls ldp configs from IOS XR, but I can from IOS XE

It's an implementation 'bug' on IOS XR.

If you have L3VPN type service (also affects labeled-ucast, including 6PE), you *must*
have 'mpls ldp' and router-id configured at minimum, even if you are not using any LDP
adjacency whatsoever. I believe ldp process needs to run to allocate labels for l3vpn,
even if you do not use LDP transport.

So, just leave 'mpls ldp' and router-id configured below it. As long as you don't
have LDP adjacencies defined, and there are no LDP tunnels configured, you won't have
any LDP in use.

P routers are not affected, as they do not need to allocate labels for VPN services.

James
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Re: RSVP-TE (MPLS-TE) and LDP question [ In reply to ]

aaron1 at gvtc

May 11, 2020, 1:32 PM

Post #3 of 3 (627 views)

Permalink

Thanks James for the confirmation as that's precisely what I'm seeing.
Would be nice to see a link to a cisco document or someone out there online
that speaks to this

-Aaron

-----Original Message-----
From: James Jun [mailto:james@towardex.com]
Sent: Monday, May 11, 2020 3:26 PM
To: Aaron Gould
Cc: cisco-nsp@puck.nether.net
Subject: Re: [c-nsp] RSVP-TE (MPLS-TE) and LDP question

On Mon, May 11, 2020 at 01:02:23PM -0500, Aaron Gould wrote:
> Seems that when I try to use RSVP in place of LDP for label distribution,
I
> cannot completely remove mpls ldp configs from IOS XR, but I can from IOS
XE

It's an implementation 'bug' on IOS XR.

If you have L3VPN type service (also affects labeled-ucast, including 6PE),
you *must*
have 'mpls ldp' and router-id configured at minimum, even if you are not
using any LDP
adjacency whatsoever. I believe ldp process needs to run to allocate labels
for l3vpn,
even if you do not use LDP transport.

So, just leave 'mpls ldp' and router-id configured below it. As long as you
don't
have LDP adjacencies defined, and there are no LDP tunnels configured, you
won't have
any LDP in use.

P routers are not affected, as they do not need to allocate labels for VPN
services.

James

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