Guide: Connecting Banyan to an on-prem AD in under 30 minutes (spoiler: it took 2 hours)

You missed the worst one. That service account needs "Replicate Directory Changes" permission on the domain itself, not just the OU. Good luck getting your AD team to sign off on that for a third-party connector without a week of paperwork.

>the only way to get that explicit list from vendors who treat their backend architecture like a state secret.

That's exactly why we just blocked the connector at the firewall and watched the logs. It'll try every endpoint it knows. You get the definitive, operational list in five minutes.

They found the local replica fine, but we had to lock it down with host entries. The site affinity settings were ignored; it kept picking the "closest" DC, which sometimes meant a WAN link. Overriding DNS with a static hosts file fixed it.

Oh, the service account permissions. That's the step that always trips up the timeline. The LDAP bind succeeds, so you think you're golden, but then the sync fails silently because it can't read the objects it needs. Been there.

We built a quick PowerShell one-liner to pre-validate the service account's actual effective permissions against a test OU before even touching the Banyan console. Saved us a round of back-and-forth with the identity team.

And you're spot on about the line-of-sight requirement. It's not just a firewall rule, it's guaranteeing the subnet route to the DCs is clean, no weird hairpinning. That discovery alone can eat an hour if your network team isn't looped in from the start.

That silent failure after a successful LDAP bind is exactly the kind of time sink that blows up project estimates. Your PowerShell pre-validation script is an excellent proactive measure; we've done something similar but used a dedicated test user object as the canary, rather than just checking the OU.

The network piece is critical, and often the last thing considered. It's not enough to just have a firewall rule. You need to confirm the routing path from the connector's subnet to the targeted DC subnet doesn't involve any intermediary devices, like firewalls or load balancers, that might silently drop LDAP traffic they consider "internal." We once lost half a day because traffic was hairpinning through a security zone that only allowed specific high ports, not 389/636. The initial ping and even a port test succeeded, but the protocol-specific packets were filtered.

Have you found that your pre-validation script also catches issues with the "Replicate Directory Changes" right, or is that a separate battle entirely?

You're absolutely right about the cross-referencing being a hidden step. I've had similar issues where the connector logs just said "authentication failure" but the DC event logs showed it was a Kerberos pre-authentication problem. That's a completely different troubleshooting path.

Is there any consistent pattern to what shows up in the Windows Security logs versus what Banyan reports? Like, does a time skew error look different than a password issue at that level?

Great observation on the Kerberos pre-auth. That's a classic one. In my experience, a pure password failure at the DC level often logs a simple 4771 (Kerberos pre-authentication failed) with a more generic status. A time skew issue can trigger a 4625 with a specific substatus like 0x12 (Account restricted), which points you right to the clock.

The real pattern I've seen is that Banyan's logs will just say "auth failed" and stop, but the DC logs show the sequence. If you see multiple 4768 (Kerberos TGT requested) events immediately followed by that 4771, it's usually password or account status. If they're spaced out or missing, think network or time sync.

That pattern check you described is crucial. I've found that a complete absence of 4768 events in the DC logs, while the connector shows generic "auth failed," almost always points to a DNS resolution failure for the KDC. The service account can't even ask for a ticket.

Your point about the sequence is key. I built a small decision matrix for my team based on exactly that correlation:

- 4768 -> 4771: Check account password/status.
- 4768 only, no 4771: Potential time skew or policy mismatch (like encryption types).
- No 4768 at all: Network/firewall blocking port 88, or DNS failure for the domain.

It turns a multi-hour log dive into a five minute check.

Ah, the classic vendor "30 minute setup." That's marketing-speak for "30 minutes if your network is a pristine lab environment and your security team has been replaced with rubber stamps." Your point about prerequisites being the real blocker is spot on.

Their entire estimate assumes you have a service account pre-baked with esoteric permissions and a network path with zero policy enforcement. In the real world, just getting the ticket opened for the "Replicate Directory Changes" permission on the domain takes longer than their entire promised setup window.

And let's not forget the real time sink: the connector's own error messages are often useless. You'll spend that extra hour and a half correlating vague "sync failed" logs with actual Windows Security events, because Banyan won't tell you it's a Kerberos pre-auth failure.

You nailed it. That "30 minutes" disclaimer should really read "30 minutes of configuration after you've done 2 hours of corporate archaeology to understand your own AD setup."

And yes, the vendor logs are next to useless. The real unlock for me was learning to have the Windows Security log from the DC open *before* hitting "Test Connection." The sequence of events there tells you the whole story, while the connector just shrugs.

So true about the corporate archaeology. I spent a day just figuring out who owned the service account we were supposed to use - it had been created for some legacy tool three years ago.

That tip about having the Windows Security log open first is gold, I'm stealing that. Do you have a quick filter you set up for those 4768/4771 events, or do you just watch the general log stream?