Two-tier distribution is invisible from inside an engineering team. You buy from a reseller, the reseller buys from a distributor, the distributor buys from the vendor, and nothing about that arrangement appears in a datasheet. What is even less visible is that the distributor employs engineers, and that those engineers have a job most people in this industry have never had described to them.
The fact that explains the whole role
Some of the resellers being supported have no technical staff at all.
That sentence does a lot of work. A reseller may be a two-person business with excellent customer relationships in a particular city or vertical, and no one who can size a firewall. It may be a larger company whose engineers are all busy delivering last quarter's projects. It may be a partner that has sold one vendor's products for a decade and has just added a second.
In all three cases, someone has to do the technical work, and the customer will not accept "our distributor is looking at it" as an answer. So the distributor's systems engineer does it, on the reseller's behalf, usually without the customer ever knowing they were there.
The bill of materials
Every project that goes through the distributor goes through the systems engineer, and the artefact is a bill of materials: the exact list of part numbers, licences, support contracts and accessories that make up a working solution.
That is harder than it sounds and it is where the value concentrates. Vendor part numbers are not self-explanatory. Licensing models change between releases. A chassis needs the right power supplies for the country, the right optics for the fibre already installed, a support contract that matches the customer's expectations rather than the one that was cheapest to quote, and often a piece nobody remembered - the rack rails, the second power feed, the licence that turns on the feature the customer thinks they already bought.
A wrong bill of materials does not fail at quote time. It fails on the loading dock, or six weeks later when a feature turns out to need a licence, and by then the reseller has a margin problem and a credibility problem in the same conversation.
Proofs of concept, and the honest version of them
A proof of concept puts the equipment in front of the customer and demonstrates that it does what was claimed. A proof of value goes further: it establishes that doing so is worth what it costs.
Running these is a distributor engineer's job more often than a vendor's, because the vendor's own engineers are aimed at large accounts and there are only so many of them. It also carries an obligation that is easy to state and harder to honour. A proof of concept designed so it cannot fail is a demonstration, not a proof, and everyone in the room knows the difference even when nobody says so. The engineer who lets a bad fit fail in a lab has saved the reseller a customer, but that is not how it feels at the time.
Presentations, and who is actually listening
The same person presents to three audiences with different needs. Customers want to know whether this solves their problem. Resellers want to know how to sell it and what it competes with. Vendors want to know that their product is being represented accurately.
A presentation that treats them as one audience satisfies none of them. Getting this right is a rhetorical skill rather than a technical one, and it is a large fraction of the working week.
Enablement, which is where teaching enters
Bootcamps, workshops, sales enablement, technical enablement. A distributor carrying dozens of vendors has resellers who need certifying on products they began selling last quarter, and the vendors' own courses are neither frequent enough nor local enough to cover it.
This is the point where distribution and instruction turn out to be the same trade approached from different ends - a pattern that shows up repeatedly in the industry timeline, where more than one large distributor was founded by teachers. The distributor's enablement is aimed at whatever its resellers are currently failing to sell, which makes it a more honest signal of what the market is struggling with than any vendor curriculum.
And the rest of it
Marketing collateral, because someone has to check that the claims in a leaflet survive contact with the product. Lead generation events. Trade shows, which are three days of the same conversation with different people and are more useful than they look, because you learn what everyone is actually being asked for. Competitive positioning. Occasionally, quietly, telling a reseller that the product they want to sell is the wrong one for that customer.
Why it is worth understanding even if you never do it
If you buy technology, some of the technical work behind your quote was probably done by someone who does not work for the company selling it to you, and whose name you will never learn. If you sell it, that person is the reason a small reseller can credibly quote a large project. And if you are an engineer wondering where the pre-sales skills of the industry are trained, a distributor's systems engineering team is one of the few places that does it at volume, across many vendors at once, under commercial pressure and with real customers on the other side of the table.