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.

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

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.

Issue thread (abstract) evaluation

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

TSG's DNS parser enforces a hard limit of exactly 17 compression-pointer jumps per query; a query with 18 jumps causes domain name extraction to fail and suppresses the injection response. Only China's GFW Injector 2 shares the full combination of DNS flags 0x8180, compression-pointer encoding in injected answers, and the 17-pointer capability boundary, confirming it runs TSG's DNS injection code.

2026-ablove-technical-analysis-geedge §6.1, Table 5 dns-poisoningdpi

Encrypted DNS protocols (DNS-over-HTTPS and DNS-over-TLS via Cloudflare 1.1.1.1, Google 8.8.8.8, AdGuard, or NextDNS) prevent DNS injection by encrypting the resolver query, making it opaque to in-path GFW middleboxes. The blog recommends these as a lightweight defense that avoids the maintenance overhead of static hosts entries.

2026-anon-6-github-dns §2 使用加密 DNS 服务 dns-poisoning

The GFW blocks GitHub by hijacking DNS resolution to incorrect IP addresses, causing browser timeouts ('github.com 响应时间太长'). The poisoning can be confirmed by comparing nslookup results against a clean resolver (8.8.8.8) versus the local ISP resolver — divergent results confirm injection.

2026-anon-6-github-dns §5 验证 DNS 污染 dns-poisoning

Static /etc/hosts bindings that hardcode correct IPs (e.g. 140.82.113.3 for github.com, 185.199.108.153 for assets-cdn.github.com) bypass DNS-injection blocking entirely, but the blog warns that GitHub IP addresses change and the file must be updated periodically to remain effective.

2026-anon-6-github-dns §1 手动修改 Hosts 文件 dns-poisoning

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