Re: LAG/ECMP and 'exact-route'

[Nitzan Tzelniker via NANOG <nanog () lists nanog org>]

For JUNOS I think that you are looking for
user@lab> show forwarding-options load-balance ?
Possible completions:
  destination-address  Destination IP address
  destination-port     Destination port
  family               Layer 3 family
  ingress-interface    Ingress Logical Interface
  packet-dump          Raw packet dump in hex without '0x'
  source-address       Source IP address
  source-port          Source port
  tos                  Type of Service field
  transport-protocol   Transport layer protocol

Nitzan

On Tue, Aug 12, 2025 at 5:58 PM Saku Ytti via NANOG <nanog () lists nanog org>
wrote:

> 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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