Re: Simple node SID TE with either SRv6 or SR-MPLS

[David Zimmerman via NANOG <nanog () lists nanog org>]

Finally found the missing glue:


[edit routing-options static route 10.10.2.0/24]

-    next-hop 10.255.0.6;

-    color 200;

+    spring-te-lsp-next-hop {

+        BLUE-TE;

+        lsp-source {

+            static;

+        }

+    }

[edit protocols source-packet-routing]

+   tunnel-tracking;

-dp

From: David Zimmerman <dzimmerman () linkedin com>
Date: Saturday, December 13, 2025 at 2:49 PM
To: nanog () lists nanog org <nanog () lists nanog org>
Subject: Simple node SID TE with either SRv6 or SR-MPLS

Hi, folks.  I’m activating the NANOG brain trust here because I’ve exhausted (and am exhausted from) efforts so far to 
seal the deal on what is probably simple stuff to y’all.

TL;DR:  I think I’m missing some specific glue to make my backbone data plane forward CE IPv4 traffic into a simple 
PE-to-PE node SID path.  I’ve tried both SRv6 steering IPv4 encap in IPv6 GRE (due to lack of End.DX4 or End.DT4) and 
SR-MPLS.  Anonymized and scrubbed topologies and configurations attached — Plan E for SRv6, Plan F* for SR-MPLS.  Using 
Junos 23.4R2-S5.6, looking for the magic “you forgot this part” for either way (though SRv6 + IPv6 GRE preferred).

Details:

I have a video partner with CEs at two sites on my internal WAN using SMPTE 2022-7 to generate two identical video 
streams.  I receive those on physically diverse links from his CEs to my PEs, then ideally carry them over diverse 
paths, which I need TE to do.  A path of node SIDs satisfies (for now) proof that I can do this (adjacency SIDs later). 
 Everything I’m doing passes Junos CLI syntax checking and “commit check” semantics, but when the change is complete, 
neither I nor my partner sees this work doing ... anything.  I should see his video test patterns having a significant 
bump in the “blue” path transcontinental end-to-end latency because I’m heading towards Canada then heading towards 
Mexico on my way between coasts.  The “red” path is almost a straight shot.

My PEs do not run BGP, so I need to do all of this entirely within IS-IS.  I believe my use of “color” in these 
configurations is a distraction that sounds like it should work but is misguided being a BGP knob.  I believe I’ve 
identified that IPv6 GRE on Junos will only use inet6.0 and will not get steered by the SID path in other tables 
despite my trying mechanisms like resolution-ribs.

I prefer to have this work with SRv6 because I’m greenfield and it’s kind of a moonshot.  But at this point I’ll defer 
to something more tried-and-true like SR-MPLS just to get things working.

Direct responses are great, public responses are cool if there are helpful learnings for others where my self-esteem in 
this space is fragile but sacrificial :-)

-dp

* Yes, “F” now stands for what you think it does

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