What you’re seeing
- Branch staff cannot reach the main office's file server, ERP system or printers.
- The firewall shows the tunnel as down, or as up but with no traffic passing.
- Logs report phase 1 or phase 2 negotiation failures or mismatched proposals.
- The tunnel comes back after a firewall reboot but drops again later.
- The outage began after an internet provider change, firmware update or IP address change.
Common causes
Every environment is different, but these are the causes our engineers find most often:
- One office's public IP address changed, so the other end is still trying to reach the old address.
- Encryption, hashing or lifetime settings no longer match on the two ends after an update or edit.
- The pre-shared key or certificate used to authenticate the tunnel was changed or expired on one side.
- The subnets defined for the tunnel do not match on both sides, so traffic is not routed through it.
- An ISP modem or upstream device is blocking or mishandling the traffic VPN tunnels depend on.
Why it matters
A down site-to-site tunnel effectively cuts a branch off from the business. Staff can't reach shared files, accounting systems, phone servers or line-of-business applications hosted at the other site or in the cloud. Customer service slows, orders queue up and remote staff sit idle. Some offices react by sending data over email or consumer cloud services, creating security gaps. The longer the outage, the more work piles up to be re-entered or reconciled afterward.
How AskTechGurus fixes it
Skip the trial and error. A certified engineer works on your actual system, finds the root cause, and fixes it properly.
Tell us what’s happening
Submit a ticket in about two minutes. Paste the error, describe what changed, and pick your tier. No charge to submit.
A certified engineer diagnoses it
A vetted, US-based systems engineer claims your ticket, usually within minutes during business hours, and investigates over a secure remote session you can watch and end at any time.
Fixed and verified with you
The engineer resolves the root cause and confirms with you that it’s working. You don’t just get a workaround, and you get a plain-English summary of what was wrong.
Pay only when it’s resolved
Fixed price from $99, invoiced only after you approve the fix. If it isn’t resolved, you don’t pay.
Frequently asked questions
Is this our ISP's fault?
Sometimes, especially after an IP address change or new modem. Often it's a configuration mismatch between the two firewalls. We confirm the cause before contacting anyone or changing anything.
Can it be fixed without someone visiting either office?
In most cases, yes. As long as at least one firewall can be reached remotely, an engineer can usually diagnose and restore the tunnel in a secure session.
Will data entered at the branch during the outage be lost?
Usually not. It is typically saved locally or queued, though some systems may need to resync once the tunnel is restored.