Category:Rahul Chaudhary

Rahul chaudhry ISP KT session. Dated 13 July 2026 - Tetra Support Staff - Takshay[edit]

Video summary: KT session on a dual-ISP failover setup built for the Rahul Chaudhry client's on-premise Zimbra mail server, which has two separate ISP links (two different public IPs) and wanted automatic failover if either link went down. Solution: a new dedicated front-end server running HAProxy, configured to load-balance all mail/web ports (443, 25, 587, 143, 993, 110, 995) roughly 50/50 across both ISP-facing IPs in normal operation, continuously health-checking the backend and shifting all traffic to the surviving link if one becomes unreachable -- verified by deliberately taking each link down in turn during testing. Also covers: Let's Encrypt SSL via certbot for the HAProxy frontend, moving DNS management for the domain over to the company's own account after recurring access problems with the client's original registrar, setting up dual MX records (different priorities, one per ISP-facing IP) so inbound mail also has a fallback path, and a note on the client-side firewall config needed for outbound failover plus keeping the SPF record in sync with whichever public IP outbound mail is actually leaving from.