Step-by-step: Bypassing ZPA for local network printers (and why you might need to).

Totally feel this. That forwarding connector trick works, but I've seen folks burn themselves on the policy scope. If you're specifying a user group like "Office_Printers," you gotta make sure your IDP group membership is *tight* and static. Last thing you want is a dynamic group rule accidentally adding external contractors because of an attribute match.

Also, port 9100 is the usual suspect, but watch out for printers using 515 (LPD) or even 631 (IPP). Might need to open a couple extra pinholes, which gets sketchy fast.

Have you considered a tiny on-prem relay service as an alternative? Like a minimal container that takes an HTTP request and forwards it raw to the printer's port, then you could hook it up via a normal webhook connector. Still a hole, but maybe a bit more auditable.

Your method highlights the core tension in ZPA's model: it's designed for cloud-first access, but on-premise devices force architectural compromises.

One nuance you didn't mention is the connector placement. That forwarding connector needs to be on a host with a network perspective that can *only* see the printer subnet, not the broader data center. Otherwise, that pinhole becomes a doorway. I typically deploy a dedicated, stripped-down VM with host firewall rules limiting egress to just the printer IP and port.

Also, monitor those connections. ZPA's logs will show the connector source IP, but you won't see the raw TCP session. You need a flow log or packet capture on the printer's segment to confirm traffic matches your policy intent. It's extra overhead, but without it you're operating blind.

Good point on the connector placement.

If you're deploying a dedicated VM anyway, consider running a flow collector on it (like ntopng in lightweight mode). You can pipe its netflow to a small timeseries DB. Then you can compare ZPA session logs with actual packet counts per destination port.

It catches misconfigurations where the printer's own queue spools traffic to other ports you didn't anticipate.

Exactly. That extra VM and host firewall config is the only thing keeping this from being a gaping security hole. The real problem is this "architectural compromise" is sold as a feature, not a workaround.

ZPA's marketing never mentions you need to spin up and harden an entire VM just to print a shipping label. That's a hidden ops cost they conveniently omit.

The flow logs are necessary, but now you've built a separate monitoring stack just for a printer. At what point does the "zero trust" overhead outweigh just putting that printer on a cloud print service?

That's a solid suggestion for layering in verification. Using flow data to correlate with ZPA's session logs is a very prudent step, especially because it can expose lateral movement you didn't intend.

One caveat I've seen is that the timestamps from the ZPA logs and the on-prem flow collector can drift, making it tricky to definitively match a specific session. It's worth setting up a small cron job on that VM to sync time aggressively with an internal NTP source, separate from the ZPA connector's own time sync.

It adds another piece of complexity, but you're right - without that, you're only seeing half the picture.

The timestamp drift is a real operational pain point for forensic correlation. While syncing with an internal NTP source helps, it doesn't solve the inherent latency between an event occurring at the connector and it being logged in ZPA's cloud service.

I've found it more reliable to generate a correlation ID on the forwarding VM itself. For each ZPA-initiated session, the local forwarding service can inject a unique ID into the TCP stream (e.g., as a PJL command for printers that support it) and also log it locally with high-resolution monotonic clock time. That gives you a concrete key to join the two log streams later, independent of clock sync.

Of course, that assumes your printer traffic can tolerate a small injected packet, which isn't universal.

That makes sense, separating the connector's network view is critical. It's similar to a principle in data pipelines where you isolate the staging server's network access to just the source database and nothing else. You're basically creating a single-purpose network gateway.

Do you have a go-to method for stripping down the VM? Like a specific minimal OS image or a set of base iptables rules you always start with?

That's a great callout on the dynamic group risk. I've been burned by that exact scenario when an HR system update suddenly added "temp" contractors to what we thought was a static security group. The audit trail was a nightmare.

Your relay service idea is interesting, especially for webhook integration. But doesn't that just move the complexity? Now you're managing a container's lifecycle, patching it, and you've still got to lock down its network egress just as tightly as the forwarding connector VM. The audit logs might be cleaner, but you're adding another moving part.

Honestly, for something as basic as printing, it often feels like we're building a Rube Goldberg machine to avoid the real question: why isn't this device on a properly segmented network with a simple, narrow firewall rule in the first place?

Exactly. You're adding operational overhead to solve a problem that shouldn't exist.

The hidden TCO is the real killer. Even a stripped-down container or VM needs patching, logging, and backup. That's easily a few hours per month in maintenance. Over a year, you could have paid for a managed cloud print service instead.

If the business case can't support that cost, then the device belongs on a simpler, isolated network segment from the start. ZPA shouldn't be a bandage for poor network design.

The container lifecycle point is valid, but the patching surface is arguably smaller than a full VM if you use a distroless base image and immutable deployments. The real tradeoff is that a containerized relay can be version-controlled and deployed identically across environments, which you can't reliably do with a manually hardened VM.

However, your closing question hits the core issue. We accept this complexity because the initial network segmentation was deemed too rigid or politically difficult. The Rube Goldberg machine gets built precisely to avoid the capital expenditure and inter-departmental friction of redesigning a legacy network segment, even when that's the technically correct answer.

Flow correlation is a smart move, especially for catching those hidden spooler ports. I've been trying to figure out how to actually set up that pipe to a timeseries DB, though.

Is ntopng's lightweight mode the best collector for this, or would something like Telegraf be easier to wire into a dashboard later? I'm worried about log volume from a busy print server.

Good question. I've been looking at this too and everyone recommends ntopng, but the learning curve seems steep for just monitoring a printer.

Telegraf with the net plugin might be simpler for a dashboard, since it's designed for InfluxDB/Grafana. But you're right to worry about volume, raw netflow from a busy server can be huge. Maybe you could start by just logging denied packets from the VM's firewall instead? That's way less data to start with.

Have you found a good dashboard for this yet, or are you building from scratch?

So your solution to zero-trust blocking a core business function is to... dismantle the zero-trust. Solid plan.

> Only do this if your local network segment is already locked down separately.
That's the real howler here. If the local segment were properly locked down, you wouldn't need the ZPA pinhole in the first place. You're advocating for a workaround that depends on the problem already being solved.

And defining a user group like "Office_Printers"? That's just a policy waiting to get bloated with exceptions when the CEO's assistant can't print. Now you're managing static IPs, group membership, and a tunnel bypass, all to avoid buying a $15 print server appliance.