This primary-source community report documents that Iran's censorship is multi-layered: VLESS+TLS successfully evades transport-protocol detection but is defeated simultaneously by DNS poisoning and CDN IP-list blocking. A circumvention tool that addresses only one layer (transport obfuscation) is insufficient for consistent access in Iran.

Iran's censorship infrastructure employs IP-list blocking of major media CDNs (Instagram, YouTube, Facebook) that remains effective against VLESS+TLS users on domestic VPS endpoints. Telegram's accessibility—because it is reachable directly by IP without domain resolution—confirms that the IP blocklist targets CDN address ranges specifically rather than applying blanket traffic inspection.

Issue thread (abstract) detection

Community analysis of the Iran VLESS+TLS failure identified DNS poisoning as a primary root cause: domain-based resolution for services like Instagram, YouTube, and Facebook was disrupted even when traffic transited a VLESS+TLS tunnel from a domestic VPS, bypassing the transport-layer obfuscation entirely.

Issue thread (abstract) detection

Iran's censorship against VLESS+TLS users on domestic VPS infrastructure is selective by destination type: Telegram, which is accessed by IP, remained reachable, while Instagram, YouTube, and Facebook were blocked or partially inaccessible. This indicates blocking operates at the destination-IP/domain layer independently of the transport protocol.

Issue thread (abstract) detection

Configuring client-side DNS settings within V2rayNG resolves the DNS poisoning component of Iran's multi-layer censorship when using VLESS+TLS from a domestic VPS. This workaround routes DNS queries through the tunnel rather than the local, poisoned resolver, restoring domain resolution for blocked services.

Issue thread (abstract) defense

The June 2025 Iran shutdown—carried out during the Iran-Israel war beginning ~June 19—did not use BGP route withdrawals as in 2019. Instead, authorities applied service-level restrictions at the national border: DNS poisoning of foreign destinations, protocol whitelisting permitting only pre-approved domestic services, and DPI to block circumvention-tool traffic. Iran's international traffic fell roughly 90% while the country's BGP routes remained advertised, making the shutdown invisible to BGP-based monitoring systems. OONI measurement volume, which totalled 121,333 in June 2025, collapsed to under 200 submissions on June 19-20.

2025-iran-shutdown-measurement Executive Summary / §2 dpidns-poisoningport-blockingip-blocking

Chinese users treat full proxy/VPN (Shadowsocks, V2Ray/Clash, commercial VPNs) as the '终极大杀器' (ultimate solution) for bypassing GitHub DNS poisoning, implying that lighter-weight DNS-only fixes fail in some network environments where the censor adds firewall-layer blocking beyond DNS.

2026-anon-6-github-dns §3 使用代理或 VPN dns-poisoningip-blocking

Rule-based proxy tools (Clash, Shadowsocks, V2Ray) are documented as the most reliable solution for accessing GitHub from China, with split-tunneling rules routing only GitHub traffic through the proxy while keeping domestic traffic on the direct path. Git command-line tools require explicit proxy configuration (git config --global http.proxy http://127.0.0.1:7890) to route clone/push operations, as they do not inherit system proxy settings automatically.

2026-anon-github-2026-6-dns §方法二 dns-poisoningip-blocking

The GFW blocks GitHub via DNS poisoning across at least four domains — github.com, assets-cdn.github.com, github.global.ssl.fastly.net, and raw.githubusercontent.com — causing connection timeouts and page-load failures for mainland China users. The block is persistent as of February 2026, affecting both browser access and command-line git operations.

2026-anon-github-2026-6-dns Introduction / §方法一 dns-poisoningip-blocking

Article 19 documents that Iran's National Information Network (NIN / SHOMA) was designed with explicit reference to China's Great Firewall as a model, with institutional mirroring: Iran's Supreme Council of Cyberspace parallels China's Cyberspace Administration of China, and both governments share a "cyber sovereignty" doctrine used to justify domestic content controls and cross-border technology transfer. The report frames Iran's filtering infrastructure as deliberately architected to replicate GFW capabilities, not as an independently developed system.

2026-article19-tightening-the-net §2, §3 dpisni-blockingdns-poisoningip-blockingbgp-hijackthrottling

Article 19 documents that Iran combines technical filtering with formal coercion of major foreign platforms (including Telegram, Instagram, and WhatsApp) to comply with content removal orders under threat of full blocking. The report notes that Iran's 2022 Women Life Freedom protests accelerated platform blocking when foreign operators refused compliance, demonstrating that the censorship system operates in two modes: coerce-and-allow for compliant platforms, block for non-compliant ones. Domain fronting via these platforms is therefore subject to sudden revocation if political conditions change.

2026-article19-tightening-the-net §6 ip-blockingdns-poisoningthrottling