LAG/ECMP and 'exact-route'

[Saku Ytti via NANOG <nanog () lists nanog org>]

Hey-o,


Which platform/software has a command to show which interface will be
used for forwarding with given keys?

ASR9k has a cef exec-route, and I see references to this in c-nsp,
reddit and cisco.com forums, stressing how useful debugging tool it
has been. Despite it not actually working, since it's just RE
software, it doesn't talk to the EZchip/lightspeed, unless it has been
fixed in the past couple of years, certainly hasn't worked in the
timeline of various forums finding it useful.

MX has 'jsim' https://www.juniper.net/documentation/en_US/day-one-books/TW_MX3D_PacketWalkthrough.pdf
which I think actually works, but it is quite involved. I have some
(false?) memory that I saw in some release note this being a bit more
productised into CLI command, but I'm failing to find anything to
support this memory.

There is also RFC5837, which is actually implemented in QFX5k, but not
for TTL exceeded, we've opened ER to get it supported on MX and PTX
and for TTL exceeded. This RFC will allow programmatic platform
agnostic discovery of the actual interface used, without relying on
platform specific magic. So please do ask your vendors to implement
it.

-- 
  ++ytti
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