How We Survived Two-Factor Authentication vs Firewall: A Head-to-Head Last quarter, our 500-person remote-first company hit a breaking point: strict corporate firewall rules were clashing with our mandatory two-factor authentication (2FA) rollout, leaving hundreds of employees locked out of critical systems. Support tickets spiked 400% in a week, and we faced a choice no security team wants: weaken firewall protections or disable 2FA. Here’s how we navigated the head-to-head clash, and what we learned from surviving it. The Core Conflict: 2FA and Firewalls 101 For context, our 2FA solution (Duo Security) requires two key network paths to function: outbound HTTPS requests from user devices to Duo’s API endpoints for OTP generation, and inbound push notification callbacks from Duo to our on-premises identity provider (IdP) for mobile approvals. Our perimeter firewall, configured with a default-deny policy for all inbound and outbound traffic, had no allowlist entries for Duo’s IP ranges or callback ports.…