I have used it successfully in a test environment that I was using ECMP in. Most of the public networks that I've worked with don't use ECMP as often as other methods for steering traffic (LAGs, BGP MEDs, etc).

What I have seen it fantastically useful for was troubleshooting a transit provider, or for when they were congested or had a flapping core link. Granted I think it's still subject to ICMP deprioritization (most SP's use it prodigiously), and most MPLS cores don't decrement TTL, but it was still useful to be able to show them "no, at this IP, I always drop traffic, when..."

- Thomas Scott | mr.thomas.scott@gmail.com

On Wed, Nov 24, 2021 at 12:23 PM Adam Thompson <athompson@merlin.mb.ca> wrote:

The tool fbtracert (http://github.com/facebookarchive/fbtracert) was mentioned here recently as a way to get visibility into multi-pathing.

Has anyone here ever used this tool successfully?

Supposedly Facebook uses this tool internally, but… that doesn’t help much.

I’ve tried it on 4 different platforms/OSes (WSL Ubuntu; RedHat; Debian; OpenBSD), and versions of Go (v1.10 through v1.16), in three very different environments (on-prem public IP; on-prem NAT’d; cloud public IP), and I’ve yet to see it produce any meaningful output – each run/iteration/thread only detects one, single, hop out of the entire chain of routers, making it less than useful. Granted, that’s not a full regression test by any means, but if anyone here has ever used it successfully, could you please let me know what sort of environment you ran it in/on?

Thanks,

-Adam

Adam Thompson
Consultant, Infrastructure Services

100 - 135 Innovation Drive
Winnipeg, MB, R3T 6A8
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