Quick sanity check before I go back into a meeting with a utility customer’s IT people.
Site is a small substation building: 14 Modbus RTU meters on two RS485 runs, a couple of transformer temperature relays, one LTE uplink plus a fiber drop that the utility’s corporate network owns. The plan is a licensed router running Edge, reading the meters and reporting them as child devices.
Their IT lead’s position is no inbound NAT, no port forwarding, no DMZ, nothing listening on a public address, period. Fine by me, but he also wants written confirmation that we will never ask for it later “when you need to log in remotely”. Previous vendor apparently started with “outbound only” and six months later asked for TCP 443 forwarded to their box for maintenance.
My understanding is the gateway dials out over TLS and that’s it. What I’m less sure about is the remote side: when my techs need to get into the router’s own web panel to fix a serial setting, how does that traffic get in without a forwarded port or a fixed IP? The LTE SIM is behind carrier NAT anyway, so a forwarded port wouldn’t even work there.
Anyone deployed this behind a strict corporate firewall? Anything outbound they need to allow besides the broker host on 8883?
Not an Edge user, but couldn’t you run a VPN from the router back to your office? That’s what we did for a web app once.
A VPN is exactly the conversation I’m trying to avoid. Their security team treats any tunnel into their network as a new project with a 3 month review.
Short version: per the docs, Edge needs no inbound access, including for remote work on the router's own panel.
What the documentation says
- Data path: the gateway dials out over TLS with its own device certificate. "Nothing on site needs to accept connections from the internet."
- Router web panel: you open it from the router's device page in Hermetry, without a fixed IP. There is no mention of port forwarding or a public address. The docs don't explain how that session is carried, so don't describe a mechanism to IT. You can quote the two statements above.
- Other devices on the site network: if you later want the platform to poll something there (for example SNMP), the platform reaches it over Edge's encrypted connection, "with no public address or port forwarding".
- Setup: claiming needs no credentials typed on site. Settings and signed firmware are pushed from Hermetry.
Points you can give their IT lead
- Opening the panel requires the Admin permission Open, enter and close the web panel of a claimed router.
- A Panel sessions list shows who opened panels. Viewing it is also Admin-only.
- There is a separate docs page, Remote access limits and audit. Read it before the meeting if they ask about logging.
- Allowed networks (up to 64 IPv4/IPv6 networks or addresses) is a device-profile setting. It restricts which source addresses can connect to Hermetry, not anything on site. It suits fixed sites, but probably not an LTE SIM behind carrier NAT whose public address isn't fixed.
Outbound rules The docs confirm MQTT over TLS on port 8883 (TLS 1.2 minimum, 1.3 preferred). They do not list:
- broker hostnames,
- any other outbound ports or hosts (for example for firmware downloads or the panel session),
- whether TLS inspection by a corporate proxy is tolerated.
Ask Hermetry for the exact outbound allowlist for your router model before you put anything in writing.
Sources
- Licensed gateways and Hermetry Edge
- Device transport security
- Gateways, polled devices and remote access
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