{"id":5245,"date":"2026-02-06T23:33:10","date_gmt":"2026-02-06T23:33:10","guid":{"rendered":"https:\/\/securitybriefing.net\/?p=5245"},"modified":"2026-02-06T23:52:27","modified_gmt":"2026-02-06T23:52:27","slug":"cach-khac-phuc-tra-cuu-dns-cham","status":"publish","type":"post","link":"https:\/\/securitybriefing.net\/vi\/cong-nghe\/cach-khac-phuc-tra-cuu-dns-cham\/","title":{"rendered":"C\u00e1ch Kh\u1eafc Ph\u1ee5c Tra C\u1ee9u DNS Ch\u1eadm"},"content":{"rendered":"<p>Tra c\u1ee9u DNS ch\u1eadm l\u00e0m t\u0103ng \u0111\u1ed9 tr\u1ec5 kh\u00f4ng c\u1ea7n thi\u1ebft tr\u01b0\u1edbc khi tr\u00ecnh duy\u1ec7t c\u1ee7a b\u1ea1n b\u1eaft \u0111\u1ea7u t\u1ea3i trang web. M\u1ed9t qu\u00e1 tr\u00ecnh ph\u00e2n gi\u1ea3i DNS th\u00f4ng th\u01b0\u1eddng m\u1ea5t 20\u2013120 ms, nh\u01b0ng DNS \u0111\u01b0\u1ee3c c\u1ea5u h\u00ecnh sai ho\u1eb7c ho\u1ea1t \u0111\u1ed9ng k\u00e9m c\u00f3 th\u1ec3 \u0111\u1ea9y th\u1eddi gian n\u00e0y v\u01b0\u1ee3t qu\u00e1 100 ms \u2014 \u0111\u00f4i khi l\u00ean \u0111\u1ebfn v\u00e0i gi\u00e2y. Th\u1eddi gian tra c\u1ee9u DNS \u1ea3nh h\u01b0\u1edfng tr\u1ef1c ti\u1ebfp \u0111\u1ebfn Th\u1eddi gian \u0111\u1ebfn Byte \u0111\u1ea7u ti\u00ean (TTFB), m\u1ed9t ch\u1ec9 s\u1ed1 Core Web Vitals. Nghi\u00ean c\u1ee9u c\u1ee7a Google cho th\u1ea5y x\u00e1c su\u1ea5t tho\u00e1t trang t\u0103ng t\u1eeb 32% \u1edf 3 gi\u00e2y l\u00ean 90% \u1edf 5 gi\u00e2y th\u1eddi gian t\u1ea3i trang. Tin t\u1ed1t: h\u1ea7u h\u1ebft c\u00e1c nguy\u00ean nh\u00e2n \u0111\u1ec1u d\u1ec5 ch\u1ea9n \u0111o\u00e1n v\u00e0 kh\u1eafc ph\u1ee5c.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n<h2 class=\"wp-block-heading\" id=\"contents\">M\u1ee5c L\u1ee5c<\/h2>\n\n\n<ol class=\"wp-block-list\">\n<li><a href=\"#causes\">Nguy\u00ean nh\u00e2n g\u00e2y ra DNS ch\u1eadm<\/a><\/li>\n\n\n\n<li><a href=\"#diagnose\">B\u01b0\u1edbc 1: Ch\u1ea9n \u0111o\u00e1n v\u1ea5n \u0111\u1ec1<\/a><\/li>\n\n\n\n<li><a href=\"#restart\">B\u01b0\u1edbc 2: Kh\u1edfi \u0111\u1ed9ng l\u1ea1i ph\u1ea7n c\u1ee9ng c\u1ee7a b\u1ea1n<\/a><\/li>\n\n\n\n<li><a href=\"#switch-dns\">B\u01b0\u1edbc 3: Chuy\u1ec3n sang nh\u00e0 cung c\u1ea5p DNS nhanh h\u01a1n<\/a><\/li>\n\n\n\n<li><a href=\"#flush\">B\u01b0\u1edbc 4: X\u00f3a b\u1ed9 nh\u1edb \u0111\u1ec7m DNS c\u1ee7a b\u1ea1n<\/a><\/li>\n\n\n\n<li><a href=\"#ipv6\">B\u01b0\u1edbc 5: Kh\u1eafc ph\u1ee5c \u0111\u1ed9 tr\u1ec5 d\u1ef1 ph\u00f2ng IPv6<\/a><\/li>\n\n\n\n<li><a href=\"#vpn\">B\u01b0\u1edbc 6: Ki\u1ec3m tra VPN, ph\u1ea7n m\u1ec1m di\u1ec7t virus &amp; b\u1ed9 \u0111i\u1ec1u h\u1ee3p Ghost<\/a><\/li>\n\n\n\n<li><a href=\"#doh\">B\u01b0\u1edbc 7: C\u1ea5u h\u00ecnh DNS qua HTTPS (DoH)<\/a><\/li>\n\n\n\n<li><a href=\"#local-cache\">B\u01b0\u1edbc 8: Ch\u1ea1y m\u00e1y ch\u1ee7 b\u1ed9 nh\u1edb \u0111\u1ec7m DNS c\u1ee5c b\u1ed9<\/a><\/li>\n\n\n\n<li><a href=\"#browser\">B\u01b0\u1edbc 9: Kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 DNS c\u1ee5 th\u1ec3 c\u1ee7a tr\u00ecnh duy\u1ec7t<\/a><\/li>\n\n\n\n<li><a href=\"#optimize-records\">B\u01b0\u1edbc 10: T\u1ed1i \u01b0u h\u00f3a b\u1ea3n ghi DNS (Ch\u1ee7 s\u1edf h\u1eefu trang web)<\/a><\/li>\n\n\n\n<li><a href=\"#reduce-domains\">B\u01b0\u1edbc 11: Gi\u1ea3m c\u00e1c mi\u1ec1n c\u1ee7a b\u00ean th\u1ee9 ba (Ch\u1ee7 s\u1edf h\u1eefu trang web)<\/a><\/li>\n\n\n\n<li><a href=\"#prefetch\">B\u01b0\u1edbc 12: Th\u1ef1c hi\u1ec7n DNS Prefetching (Nh\u00e0 ph\u00e1t tri\u1ec3n web)<\/a><\/li>\n\n\n\n<li><a href=\"#troubleshooting\">B\u1ea3ng tham kh\u1ea3o nhanh v\u1ec1 kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1<\/a><\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n<h2 class=\"wp-block-heading\" id=\"causes\">Nguy\u00ean nh\u00e2n g\u00e2y ra DNS ch\u1eadm<\/h2>\n\n\n<p>Nhi\u1ec1u y\u1ebfu t\u1ed1 g\u00f3p ph\u1ea7n v\u00e0o \u0111\u1ed9 tr\u1ec5 DNS:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>M\u00e1y ch\u1ee7 DNS do ISP cung c\u1ea5p ch\u1eadm<\/strong> \u2014 Tr\u00ecnh ph\u00e2n gi\u1ea3i m\u1eb7c \u0111\u1ecbnh t\u1eeb ISP c\u1ee7a b\u1ea1n th\u01b0\u1eddng ch\u1eadm h\u01a1n \u0111\u00e1ng k\u1ec3 so v\u1edbi c\u00e1c l\u1ef1a ch\u1ecdn thay th\u1ebf c\u00f4ng c\u1ed9ng. DNS mi\u1ec5n ph\u00ed t\u1eeb c\u00e1c nh\u00e0 \u0111\u0103ng k\u00fd nh\u01b0 GoDaddy v\u00e0 Namecheap c\u0169ng th\u01b0\u1eddng ch\u1eadm.<\/li>\n\n\n\n<li><strong>Kho\u1ea3ng c\u00e1ch \u0111\u1ecba l\u00fd<\/strong> \u2014 M\u00e1y ch\u1ee7 DNS c\u00e0ng xa b\u1ea1n, th\u1eddi gian \u0111i v\u00f2ng c\u00e0ng l\u00e2u.<\/li>\n\n\n\n<li><strong>\u0110\u1ed9 tr\u1ec5 d\u1ef1 ph\u00f2ng IPv6<\/strong> \u2014 H\u1ec7 \u0111i\u1ec1u h\u00e0nh hi\u1ec7n \u0111\u1ea1i \u01b0u ti\u00ean tra c\u1ee9u IPv6 (AAAA). N\u1ebfu ISP c\u1ee7a b\u1ea1n h\u1ed7 tr\u1ee3 IPv6 k\u00e9m, thi\u1ebft b\u1ecb c\u1ee7a b\u1ea1n s\u1ebd treo \u0111\u1ebfn 5 gi\u00e2y tr\u01b0\u1edbc khi quay l\u1ea1i IPv4.<\/li>\n\n\n\n<li><strong>B\u1ea3n ghi DNS qu\u00e1 m\u1ee9c<\/strong> \u2014 C\u00e1c b\u1ea3n ghi A, CNAME v\u00e0 TXT kh\u00f4ng s\u1eed d\u1ee5ng ho\u1eb7c l\u1ed7i th\u1eddi l\u00e0m t\u0103ng t\u1ea3i cho tra c\u1ee9u.<\/li>\n\n\n\n<li><strong>Chu\u1ed7i CNAME<\/strong> \u2014 Nhi\u1ec1u chuy\u1ec3n h\u01b0\u1edbng (CNAME \u2192 CNAME \u2192 b\u1ea3n ghi A) bu\u1ed9c tra c\u1ee9u tu\u1ea7n t\u1ef1 l\u00e0m t\u0103ng \u0111\u1ed9 tr\u1ec5.<\/li>\n\n\n\n<li><strong>Kh\u00f4ng c\u00f3 b\u1ed9 nh\u1edb \u0111\u1ec7m DNS<\/strong> \u2014 Kh\u00f4ng c\u00f3 b\u1ed9 nh\u1edb \u0111\u1ec7m, c\u00e1c truy v\u1ea5n DNS gi\u1ed1ng nhau l\u1eb7p l\u1ea1i tr\u00ean m\u1ed7i l\u1ea7n t\u1ea3i trang.<\/li>\n\n\n\n<li><strong>M\u00e1y ch\u1ee7 t\u00ean qu\u00e1 t\u1ea3i<\/strong> \u2014 C\u00e1c nh\u00e0 cung c\u1ea5p d\u1ecbch v\u1ee5 l\u01b0u tr\u1eef v\u1edbi m\u00e1y ch\u1ee7 t\u00ean kh\u00f4ng \u0111\u1ee7 cung c\u1ea5p g\u00e2y ra \u0111\u1ed9 tr\u1ec5.<\/li>\n\n\n\n<li><strong>T\u1eafc ngh\u1ebdn m\u1ea1ng v\u00e0 \u0111\u1ecbnh tuy\u1ebfn kh\u00f4ng t\u1ed1i \u01b0u<\/strong> \u2014 Ngay c\u1ea3 m\u1ed9t m\u00e1y ch\u1ee7 g\u1ea7n \u0111\u00f3 c\u0169ng c\u00f3 th\u1ec3 ch\u1eadm n\u1ebfu \u0111\u01b0\u1eddng d\u1eabn \u0111\u1ebfn n\u00f3 b\u1ecb t\u1eafc ngh\u1ebdn.<\/li>\n\n\n\n<li><strong>Can thi\u1ec7p VPN v\u00e0 proxy<\/strong> \u2014 VPN \u0111\u1ecbnh tuy\u1ebfn DNS qua m\u00e1y ch\u1ee7 c\u1ee7a ri\u00eang h\u1ecd, c\u00f3 th\u1ec3 ch\u1eadm h\u01a1n. M\u1ed9t s\u1ed1 r\u00f2 r\u1ec9 truy v\u1ea5n DNS ra ngo\u00e0i \u0111\u01b0\u1eddng h\u1ea7m.<\/li>\n\n\n\n<li><strong>B\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng Ghost<\/strong> \u2014 B\u1ed9 \u0111i\u1ec1u h\u1ee3p \u1ea3o t\u1eeb ph\u1ea7n m\u1ec1m VPN, m\u00e1y \u1ea3o ho\u1eb7c Docker gi\u1eef c\u1ea5u h\u00ecnh DNS l\u1ed7i th\u1eddi g\u00e2y c\u1ea3n tr\u1edf vi\u1ec7c ph\u00e2n gi\u1ea3i.<\/li>\n\n\n\n<li><strong>L\u1ecdc DNS c\u1ee7a ph\u1ea7n m\u1ec1m di\u1ec7t virus\/t\u01b0\u1eddng l\u1eeda<\/strong> \u2014 M\u1ed9t s\u1ed1 ph\u1ea7n m\u1ec1m b\u1ea3o m\u1eadt (Norton, Kaspersky, Bitdefender) ch\u1eb7n truy v\u1ea5n DNS, l\u00e0m t\u0103ng \u0111\u1ed9 tr\u1ec5.<\/li>\n\n\n\n<li><strong>Ghi \u0111\u00e8 DNS \u1edf c\u1ea5p tr\u00ecnh duy\u1ec7t<\/strong> \u2014 Chrome, Firefox v\u00e0 Edge c\u00f3 th\u1ec3 \u00e2m th\u1ea7m ghi \u0111\u00e8 c\u00e0i \u0111\u1eb7t DNS c\u1ee7a h\u1ec7 \u0111i\u1ec1u h\u00e0nh v\u1edbi c\u1ea5u h\u00ecnh DNS qua HTTPS (DoH) t\u00edch h\u1ee3p c\u1ee7a ri\u00eang h\u1ecd.<\/li>\n\n\n\n<li><strong>Qu\u00e1 nhi\u1ec1u mi\u1ec1n c\u1ee7a b\u00ean th\u1ee9 ba<\/strong> \u2014 M\u1ed7i mi\u1ec1n duy nh\u1ea5t m\u00e0 trang web c\u1ee7a b\u1ea1n t\u1ea3i y\u00eau c\u1ea7u m\u1ed9t tra c\u1ee9u DNS ri\u00eang bi\u1ec7t, l\u00e0m t\u0103ng t\u1ed5ng th\u1eddi gian t\u1ea3i trang.<\/li>\n\n\n\n<li><strong>Kh\u00f4ng c\u1ea5u h\u00ecnh DNS th\u1ee9 c\u1ea5p<\/strong> \u2014 Kh\u00f4ng c\u00f3 m\u00e1y ch\u1ee7 DNS d\u1ef1 ph\u00f2ng, h\u1ec7 th\u1ed1ng s\u1ebd treo ch\u1edd th\u1eddi gian ch\u1edd n\u1ebfu m\u00e1y ch\u1ee7 ch\u00ednh b\u1ecb h\u1ecfng ho\u1eb7c ch\u1eadm.<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\" id=\"diagnose\">B\u01b0\u1edbc 1: Ch\u1ea9n \u0111o\u00e1n v\u1ea5n \u0111\u1ec1<\/h2>\n\n\n<p>Tr\u01b0\u1edbc khi s\u1eeda b\u1ea5t c\u1ee9 \u0111i\u1ec1u g\u00ec, h\u00e3y x\u00e1c nh\u1eadn DNS th\u1ef1c s\u1ef1 l\u00e0 n\u00fat th\u1eaft c\u1ed5 chai.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"using-dig-linuxmacos\">S\u1eed d\u1ee5ng dig (Linux\/macOS)<\/h3>\n\n\n<p>C\u00e1c <code>\u0111\u00e0o<\/code> l\u1ec7nh l\u00e0 c\u00f4ng c\u1ee5 ch\u00ednh \u0111\u1ec3 \u0111o th\u1eddi gian ph\u1ea3n h\u1ed3i DNS:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>1. Truy v\u1ea5n m\u1ed9t m\u00e1y ch\u1ee7 DNS c\u1ee5 th\u1ec3 v\u00e0 ki\u1ec3m tra th\u1eddi gian ph\u1ea3n h\u1ed3i<br>\u0111\u00e0o example.com @8.8.8.8<br><br>1. D\u1ea5u v\u1ebft l\u1eb7p \u0111\u1ea7y \u0111\u1ee7 hi\u1ec3n th\u1ecb \u0111\u1ed9 tr\u1ec5 c\u1ee7a t\u1eebng b\u01b0\u1edbc nh\u1ea3y<br>\u0111\u00e0o example.com +trace<\/samp><\/p>\n<\/blockquote>\n\n\n\n<p>\u0110\u1ea7u ra bao g\u1ed3m m\u1ed9t <code>Th\u1eddi gian truy v\u1ea5n<\/code> tr\u01b0\u1eddng (v\u00ed d\u1ee5: 34 ms). N\u1ebfu \u0111i\u1ec1u n\u00e0y v\u01b0\u1ee3t qu\u00e1 100 ms, l\u1edbp DNS l\u00e0 m\u1ed9t v\u1ea5n \u0111\u1ec1 hi\u1ec7u su\u1ea5t. L\u00fd t\u01b0\u1edfng nh\u1ea5t l\u00e0 nh\u1eafm \u0111\u1ebfn d\u01b0\u1edbi 50 ms.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"using-nslookup-windows\">S\u1eed d\u1ee5ng nslookup (Windows)<\/h3>\n\n\n<p>\u0110\u1ed1i v\u1edbi ng\u01b0\u1eddi d\u00f9ng Windows, <code>nslookup<\/code> l\u00e0 c\u00f4ng c\u1ee5 ch\u1ea9n \u0111o\u00e1n DNS m\u1eb7c \u0111\u1ecbnh:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>1. Tra c\u1ee9u DNS c\u01a1 b\u1ea3n<br>nslookup example.com<br><br>1. Truy v\u1ea5n m\u1ed9t m\u00e1y ch\u1ee7 DNS c\u1ee5 th\u1ec3<br>nslookup example.com 8.8.8.8<br><br>1. Ki\u1ec3m tra m\u00e1y ch\u1ee7 t\u00ean cho m\u1ed9t mi\u1ec1n<br>nslookup -type=ns example.com<\/samp><\/p>\n<\/blockquote>\n\n\n\n<p>N\u1ebfu <code>nslookup<\/code> tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 nhanh ch\u00f3ng nh\u01b0ng duy\u1ec7t web c\u1ea3m th\u1ea5y ch\u1eadm, v\u1ea5n \u0111\u1ec1 c\u00f3 th\u1ec3 l\u00e0 DNS \u1edf c\u1ea5p tr\u00ecnh duy\u1ec7t, d\u1ef1 ph\u00f2ng IPv6 ho\u1eb7c can thi\u1ec7p VPN \u2014 kh\u00f4ng ph\u1ea3i m\u00e1y ch\u1ee7 DNS t\u1ef1 n\u00f3.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"using-ping-and-traceroute\">S\u1eed d\u1ee5ng ping v\u00e0 traceroute<\/h3>\n\n\n<p>Ki\u1ec3m tra \u0111\u1ed9 tr\u1ec5 m\u1ea1ng th\u00f4 \u0111\u1ebfn m\u00e1y ch\u1ee7 DNS c\u1ee7a b\u1ea1n \u0111\u1ec3 t\u00e1ch bi\u1ec7t c\u00e1c v\u1ea5n \u0111\u1ec1 m\u1ea1ng kh\u1ecfi c\u00e1c v\u1ea5n \u0111\u1ec1 \u1ee9ng d\u1ee5ng DNS:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>1. Linux\/macOS<br>ping -c 3 8.8.8.8<br>traceroute 8.8.8.8<br><br>1. Windows<br>ping 8.8.8.8<br>tracert 8.8.8.8<\/samp><\/p>\n<\/blockquote>\n\n\n\n<p>N\u1ebfu ping cho th\u1ea5y \u0111\u1ed9 tr\u1ec5 cao nh\u01b0ng <code>\u0111\u00e0o<\/code> \u0111\u1ebfn c\u00f9ng m\u1ed9t m\u00e1y ch\u1ee7 ch\u1eadm theo t\u1ef7 l\u1ec7, v\u1ea5n \u0111\u1ec1 l\u00e0 kho\u1ea3ng c\u00e1ch m\u1ea1ng, kh\u00f4ng ph\u1ea3i m\u00e1y ch\u1ee7 DNS t\u1ef1 n\u00f3.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"600\" height=\"350\" src=\"https:\/\/securitybriefing.net\/wp-content\/uploads\/2026\/02\/Slow-DNS-Lookup.jpg\" alt=\"Tra c\u1ee9u DNS ch\u1eadm\" class=\"wp-image-5246\" srcset=\"https:\/\/securitybriefing.net\/wp-content\/uploads\/2026\/02\/Slow-DNS-Lookup.jpg 600w, https:\/\/securitybriefing.net\/wp-content\/uploads\/2026\/02\/Slow-DNS-Lookup-300x175.jpg 300w, https:\/\/securitybriefing.net\/wp-content\/uploads\/2026\/02\/Slow-DNS-Lookup-18x12.jpg 18w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/figure>\n\n\n<h3 class=\"wp-block-heading\" id=\"dns-benchmark-tools\">C\u00f4ng c\u1ee5 \u0111o \u0111i\u1ec3m chu\u1ea9n DNS<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li><strong>GRC DNS Benchmark<\/strong> \u2014 M\u1ed9t ti\u1ec7n \u00edch Windows ki\u1ec3m tra h\u00e0ng ch\u1ee5c m\u00e1y ch\u1ee7 DNS v\u00e0 x\u1ebfp h\u1ea1ng ch\u00fang theo t\u1ed1c \u0111\u1ed9 t\u1eeb v\u1ecb tr\u00ed c\u1ee7a b\u1ea1n. R\u1ea5t \u0111\u01b0\u1ee3c khuy\u1ebfn kh\u00edch \u0111\u1ec3 t\u00ecm tr\u00ecnh ph\u00e2n gi\u1ea3i nhanh nh\u1ea5t cho m\u1ea1ng c\u1ee5 th\u1ec3 c\u1ee7a b\u1ea1n.<\/li>\n\n\n\n<li><strong>Namebench<\/strong> \u2014 C\u00f4ng c\u1ee5 thu\u1ed9c s\u1edf h\u1eefu c\u1ee7a Google t\u00ecm ki\u1ebfm c\u00e1c m\u00e1y ch\u1ee7 DNS nhanh nh\u1ea5t c\u00f3 s\u1eb5n cho m\u00e1y t\u00ednh c\u1ee7a b\u1ea1n.<\/li>\n\n\n\n<li><strong>DNSPerf<\/strong> \u2014 M\u1ed9t c\u00f4ng c\u1ee5 m\u00e3 ngu\u1ed3n m\u1edf \u0111\u1ec3 \u0111o \u0111i\u1ec3m chu\u1ea9n c\u00e1c m\u00e1y ch\u1ee7 DNS quy\u1ec1n l\u1ef1c d\u01b0\u1edbi t\u1ea3i.<\/li>\n\n\n\n<li><strong>dnsdiag (dnsping, dnstraceroute, dnseval)<\/strong> \u2014 M\u1ed9t b\u1ed9 c\u00f4ng c\u1ee5 Python \u0111\u1ec3 \u0111o DNS. C\u00e0i \u0111\u1eb7t qua <code>pip3 c\u00e0i \u0111\u1eb7t dnsdiag<\/code>.<\/li>\n\n\n\n<li><strong>dnsspeedtest.site<\/strong> \u2014 M\u1ed9t c\u00f4ng c\u1ee5 d\u1ef1a tr\u00ean tr\u00ecnh duy\u1ec7t \u0111o \u0111i\u1ec3m chu\u1ea9n h\u01a1n 20 nh\u00e0 cung c\u1ea5p DNS s\u1eed d\u1ee5ng DNS qua HTTPS m\u00e0 kh\u00f4ng c\u1ea7n c\u00e0i \u0111\u1eb7t ph\u1ea7n m\u1ec1m.<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\" id=\"restart\">B\u01b0\u1edbc 2: Kh\u1edfi \u0111\u1ed9ng l\u1ea1i ph\u1ea7n c\u1ee9ng c\u1ee7a b\u1ea1n<\/h2>\n\n\n<p>C\u00e1ch s\u1eeda \u0111\u01a1n gi\u1ea3n nh\u1ea5t th\u01b0\u1eddng b\u1ecb b\u1ecf qua. Kh\u1edfi \u0111\u1ed9ng l\u1ea1i b\u1ed9 \u0111\u1ecbnh tuy\u1ebfn c\u1ee7a b\u1ea1n s\u1ebd x\u00f3a b\u1ed9 nh\u1edb \u0111\u1ec7m DNS n\u1ed9i b\u1ed9 c\u1ee7a n\u00f3 v\u00e0 c\u00f3 th\u1ec3 gi\u1ea3i quy\u1ebft c\u00e1c v\u1ea5n \u0111\u1ec1 \u0111\u1ecbnh tuy\u1ebfn. Nhi\u1ec1u b\u1ed9 \u0111\u1ecbnh tuy\u1ebfn ISP c\u00f3 b\u1ed9 chuy\u1ec3n ti\u1ebfp DNS t\u00edch h\u1ee3p c\u00f3 th\u1ec3 b\u1ecb qu\u00e1 t\u1ea3i ho\u1eb7c l\u1ed7i th\u1eddi theo th\u1eddi gian.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>R\u00fat ph\u00edch c\u1eafm b\u1ed9 \u0111\u1ecbnh tuy\u1ebfn c\u1ee7a b\u1ea1n trong 30 gi\u00e2y, sau \u0111\u00f3 c\u1eafm l\u1ea1i.<\/li>\n\n\n\n<li>Kh\u1edfi \u0111\u1ed9ng l\u1ea1i PC, \u0111i\u1ec7n tho\u1ea1i ho\u1eb7c m\u00e1y t\u00ednh b\u1ea3ng c\u1ee7a b\u1ea1n.<\/li>\n\n\n\n<li>N\u1ebfu s\u1eed d\u1ee5ng modem ri\u00eang, h\u00e3y kh\u1edfi \u0111\u1ed9ng l\u1ea1i n\u00f3.<\/li>\n<\/ul>\n\n\n\n<p>\u0110i\u1ec1u n\u00e0y x\u00f3a c\u00e1c s\u1ef1 c\u1ed1 t\u1ea1m th\u1eddi v\u00e0 bu\u1ed9c c\u00e1c k\u1ebft n\u1ed1i DNS m\u1edbi. H\u00e3y th\u1eed \u0111i\u1ec1u n\u00e0y tr\u01b0\u1edbc b\u1ea5t k\u1ef3 s\u1eeda ch\u1eefa n\u00e0o kh\u00e1c.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"switch-dns\">B\u01b0\u1edbc 3: Chuy\u1ec3n sang nh\u00e0 cung c\u1ea5p DNS nhanh h\u01a1n<\/h2>\n\n\n<p>\u0110\u00e2y l\u00e0 c\u00e1ch s\u1eeda ch\u1eefa c\u00f3 t\u00e1c \u0111\u1ed9ng l\u1edbn nh\u1ea5t \u0111\u1ed1i v\u1edbi h\u1ea7u h\u1ebft ng\u01b0\u1eddi d\u00f9ng. Thay th\u1ebf DNS m\u1eb7c \u0111\u1ecbnh c\u1ee7a ISP c\u1ee7a b\u1ea1n b\u1eb1ng m\u1ed9t tr\u00ecnh ph\u00e2n gi\u1ea3i c\u00f4ng c\u1ed9ng nhanh h\u01a1n. Lu\u00f4n c\u1ea5u h\u00ecnh c\u1ea3 DNS ch\u00ednh v\u00e0 ph\u1ee5 \u2014 kh\u00f4ng c\u00f3 d\u1ef1 ph\u00f2ng, h\u1ec7 th\u1ed1ng s\u1ebd treo ch\u1edd th\u1eddi gian ch\u1edd n\u1ebfu m\u00e1y ch\u1ee7 ch\u00ednh b\u1ecb h\u1ecfng ho\u1eb7c ch\u1eadm.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th>Nh\u00e0 cung c\u1ea5p<\/th><th>Ch\u00ednh<\/th><th>Ph\u1ee5<\/th><th>\u0110i\u1ec3m m\u1ea1nh<\/th><\/tr><tr><td>\u0110\u00e1m m\u00e2y<\/td><td>1.1.1.1<\/td><td>1.0.0.1<\/td><td>Th\u01b0\u1eddng l\u00e0 nhanh nh\u1ea5t tr\u00ean to\u00e0n c\u1ea7u; ch\u00ednh s\u00e1ch b\u1ea3o m\u1eadt m\u1ea1nh m\u1ebd; kh\u00f4ng h\u1ed7 tr\u1ee3 EDNS Client Subnet (b\u1ed9 nh\u1edb \u0111\u1ec7m t\u00edch c\u1ef1c h\u01a1n).<\/td><\/tr><tr><td>DNS c\u00f4ng c\u1ed9ng c\u1ee7a Google<\/td><td>8.8.8.8<\/td><td>8.8.4.4<\/td><td>C\u1ef1c k\u1ef3 \u0111\u00e1ng tin c\u1eady; th\u1eddi gian ho\u1ea1t \u0111\u1ed9ng cao; h\u1ed7 tr\u1ee3 EDNS Client Subnet \u0111\u1ec3 \u0111\u1ecbnh tuy\u1ebfn CDN t\u1ed1t h\u01a1n.<\/td><\/tr><tr><td>Quad9<\/td><td>9.9.9.9<\/td><td>149.112.112.112<\/td><td>Ch\u1eb7n c\u00e1c mi\u1ec1n \u0111\u1ed9c h\u1ea1i \u0111\u00e3 bi\u1ebft; t\u1eadp trung m\u1ea1nh v\u00e0o b\u1ea3o m\u1eadt.<\/td><\/tr><tr><td>OpenDNS<\/td><td>208.67.222.222<\/td><td>208.67.220.220<\/td><td>X\u1eed l\u00fd truy v\u1ea5n nhanh; c\u00e1c t\u00f9y ch\u1ecdn l\u1ecdc n\u1ed9i dung; ki\u1ec3m so\u00e1t c\u1ee7a ph\u1ee5 huynh.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><strong>L\u01b0u \u00fd v\u1ec1 Cloudflare so v\u1edbi Google:<\/strong> Nghi\u00ean c\u1ee9u c\u1ee7a ThousandEyes cho th\u1ea5y Cloudflare cung c\u1ea5p ph\u00e2n gi\u1ea3i DNS ngang b\u1eb1ng v\u1edbi c\u00e1c m\u00e1y ch\u1ee7 ISP (trung b\u00ecnh 23,4 ms) trong khi Google trung b\u00ecnh l\u00e0 48,8 ms. Tuy nhi\u00ean, h\u1ed7 tr\u1ee3 EDNS Client Subnet c\u1ee7a Google c\u00f3 th\u1ec3 c\u1ea3i thi\u1ec7n t\u1ef7 l\u1ec7 truy c\u1eadp b\u1ed9 nh\u1edb \u0111\u1ec7m CDN. Ch\u1ecdn d\u1ef1a tr\u00ean \u01b0u ti\u00ean c\u1ee7a b\u1ea1n: t\u1ed1c \u0111\u1ed9 th\u00f4 (Cloudflare) ho\u1eb7c t\u1ed1i \u01b0u h\u00f3a CDN (Google).<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"how-to-change-dns-on-windows\">C\u00e1ch thay \u0111\u1ed5i DNS tr\u00ean Windows<\/h3>\n\n\n<p>M\u1edf C\u00e0i \u0111\u1eb7t \u2192 M\u1ea1ng &amp; Internet \u2192 Ethernet (ho\u1eb7c Wi-Fi). Nh\u1ea5p v\u00e0o Ch\u1ec9nh s\u1eeda b\u00ean c\u1ea1nh g\u00e1n m\u00e1y ch\u1ee7 DNS. Chuy\u1ec3n sang Th\u1ee7 c\u00f4ng, b\u1eadt IPv4 v\u00e0 nh\u1eadp \u0111\u1ecba ch\u1ec9 DNS \u01b0a th\u00edch c\u1ee7a b\u1ea1n.<\/p>\n\n\n\n<p>Ngo\u00e0i ra, qua Command Prompt:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>netsh interface ip add dns name=&#8221;Ethernet&#8221; addr=1.1.1.1 index=1<br>netsh interface ip add dns name=&#8221;Ethernet&#8221; addr=1.0.0.1 index=2<\/samp><\/p>\n<\/blockquote>\n\n\n<h3 class=\"wp-block-heading\" id=\"how-to-change-dns-on-macoslinux\">C\u00e1ch thay \u0111\u1ed5i DNS tr\u00ean macOS\/Linux<\/h3>\n\n\n<p>Tr\u00ean macOS, \u0111i t\u1edbi C\u00e0i \u0111\u1eb7t H\u1ec7 th\u1ed1ng \u2192 M\u1ea1ng \u2192 k\u1ebft n\u1ed1i c\u1ee7a b\u1ea1n \u2192 DNS v\u00e0 th\u00eam IP c\u1ee7a tr\u00ecnh ph\u00e2n gi\u1ea3i. Tr\u00ean Linux, ch\u1ec9nh s\u1eeda <code>\/etc\/resolv.conf<\/code> ho\u1eb7c c\u1ea5u h\u00ecnh qua tr\u00ecnh qu\u1ea3n l\u00fd m\u1ea1ng c\u1ee7a b\u1ea1n:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>1. Linux: Ch\u1ec9nh s\u1eeda \/etc\/resolv.conf<br>sudo nano \/etc\/resolv.conf<br><br>1. Th\u00eam c\u00e1c d\u00f2ng n\u00e0y:<br>nameserver 1.1.1.1<br>nameserver 1.0.0.1<\/samp><\/p>\n<\/blockquote>\n\n\n<h3 class=\"wp-block-heading\" id=\"change-dns-on-your-router\">Thay \u0111\u1ed5i DNS tr\u00ean b\u1ed9 \u0111\u1ecbnh tuy\u1ebfn c\u1ee7a b\u1ea1n<\/h3>\n\n\n<p>\u0110\u1ec3 thay \u0111\u1ed5i tr\u00ean to\u00e0n m\u1ea1ng, c\u1eadp nh\u1eadt c\u00e0i \u0111\u1eb7t DNS trong b\u1ea3ng qu\u1ea3n tr\u1ecb c\u1ee7a b\u1ed9 \u0111\u1ecbnh tuy\u1ebfn c\u1ee7a b\u1ea1n (th\u01b0\u1eddng l\u00e0 t\u1ea1i 192.168.1.1 ho\u1eb7c 192.168.0.1). \u0110i\u1ec1u n\u00e0y \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u1ea5t c\u1ea3 c\u00e1c thi\u1ebft b\u1ecb tr\u00ean m\u1ea1ng \u2014 b\u1ea1n ch\u1ec9 c\u1ea7n c\u1ea5u h\u00ecnh m\u1ed9t l\u1ea7n thay v\u00ec tr\u00ean t\u1eebng thi\u1ebft b\u1ecb.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"flush\">B\u01b0\u1edbc 4: X\u00f3a b\u1ed9 nh\u1edb \u0111\u1ec7m DNS c\u1ee7a b\u1ea1n<\/h2>\n\n\n<p>C\u00e1c m\u1ee5c b\u1ed9 nh\u1edb \u0111\u1ec7m l\u1ed7i th\u1eddi ho\u1eb7c b\u1ecb h\u1ecfng c\u00f3 th\u1ec3 g\u00e2y ra l\u1ed7i ph\u00e2n gi\u1ea3i ho\u1eb7c chuy\u1ec3n h\u01b0\u1edbng \u0111\u1ebfn c\u00e1c IP sai. X\u00f3a b\u1ed9 nh\u1edb \u0111\u1ec7m bu\u1ed9c c\u00e1c tra c\u1ee9u m\u1edbi:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th>H\u1ec7 \u0111i\u1ec1u h\u00e0nh<\/th><th>L\u1ec7nh<\/th><\/tr><tr><td>Windows 10\/11<\/td><td><code>ipconfig \/flushdns<\/code><\/td><\/tr><tr><td>macOS (Ventura+)<\/td><td><code>sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder<\/code><\/td><\/tr><tr><td>Linux (systemd)<\/td><td><code>sudo systemd-resolve --flush-caches<\/code> ho\u1eb7c <code>sudo resolvectl flush-caches<\/code><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\u0110\u1eebng qu\u00ean b\u1ed9 nh\u1edb \u0111\u1ec7m \u1edf c\u1ea5p tr\u00ecnh duy\u1ec7t. Trong Chrome, \u0111i\u1ec1u h\u01b0\u1edbng \u0111\u1ebfn <code>chrome:\/\/net-internals\/#dns<\/code> v\u00e0 nh\u1ea5p v\u00e0o \u201cX\u00f3a b\u1ed9 nh\u1edb \u0111\u1ec7m m\u00e1y ch\u1ee7\u201d. Trong Firefox, b\u1ed9 nh\u1edb \u0111\u1ec7m DNS s\u1ebd \u0111\u01b0\u1ee3c x\u00f3a khi b\u1ea1n kh\u1edfi \u0111\u1ed9ng l\u1ea1i tr\u00ecnh duy\u1ec7t ho\u1eb7c c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c x\u00f3a qua <code>about:networking#dns<\/code>.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"ipv6\">B\u01b0\u1edbc 5: Kh\u1eafc ph\u1ee5c \u0111\u1ed9 tr\u1ec5 d\u1ef1 ph\u00f2ng IPv6<\/h2>\n\n\n<p>\u0110\u00e2y l\u00e0 m\u1ed9t trong nh\u1eefng nguy\u00ean nh\u00e2n \u1ea9n ph\u1ed5 bi\u1ebfn nh\u1ea5t g\u00e2y ra DNS ch\u1eadm m\u00e0 c\u00e1c h\u01b0\u1edbng d\u1eabn ti\u00eau chu\u1ea9n b\u1ecf qua. H\u1ec7 \u0111i\u1ec1u h\u00e0nh hi\u1ec7n \u0111\u1ea1i \u01b0u ti\u00ean tra c\u1ee9u IPv6 (AAAA) h\u01a1n IPv4. N\u1ebfu ISP c\u1ee7a b\u1ea1n c\u00f3 h\u1ed7 tr\u1ee3 IPv6 k\u00e9m ho\u1eb7c kh\u00f4ng c\u00f3, thi\u1ebft b\u1ecb c\u1ee7a b\u1ea1n s\u1ebd ch\u1edd \u0111\u1ebfn 5 gi\u00e2y \u0111\u1ec3 nh\u1eadn ph\u1ea3n h\u1ed3i IPv6 tr\u01b0\u1edbc khi quay l\u1ea1i IPv4. \u0110i\u1ec1u n\u00e0y x\u1ea3y ra tr\u00ean m\u1ed7i k\u1ebft n\u1ed1i m\u1edbi.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"how-to-diagnose\">C\u00e1ch ch\u1ea9n \u0111o\u00e1n<\/h3>\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>1. Ki\u1ec3m tra k\u1ebft n\u1ed1i IPv6<br>ping -6 google.com<br><br>1. N\u1ebfu \u0111i\u1ec1u n\u00e0y h\u1ebft th\u1eddi gian ho\u1eb7c m\u1ea5t v\u00e0i gi\u00e2y, IPv6 l\u00e0 v\u1ea5n \u0111\u1ec1<br>1. So s\u00e1nh v\u1edbi IPv4:<br>ping -4 google.com<\/samp><\/p>\n<\/blockquote>\n\n\n<h3 class=\"wp-block-heading\" id=\"how-to-fix\">C\u00e1ch kh\u1eafc ph\u1ee5c<\/h3>\n\n\n<p><strong>T\u00f9y ch\u1ecdn 1: V\u00f4 hi\u1ec7u h\u00f3a IPv6 tr\u00ean b\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng<\/strong> (n\u1ebfu ISP c\u1ee7a b\u1ea1n kh\u00f4ng h\u1ed7 tr\u1ee3 n\u00f3)<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Windows: Thu\u1ed9c t\u00ednh b\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng \u2192 b\u1ecf ch\u1ecdn \u201cInternet Protocol Version 6 (TCP\/IPv6)\u201d<\/li>\n\n\n\n<li>Linux: Th\u00eam <code>net.ipv6.conf.all.disable_ipv6 = 1<\/code> \u0110\u1ebeN <code>\/etc\/sysctl.conf<\/code><\/li>\n\n\n\n<li>macOS: C\u00e0i \u0111\u1eb7t H\u1ec7 th\u1ed1ng \u2192 M\u1ea1ng \u2192 k\u1ebft n\u1ed1i c\u1ee7a b\u1ea1n \u2192 TCP\/IP \u2192 C\u1ea5u h\u00ecnh IPv6 \u2192 Ch\u1ec9 li\u00ean k\u1ebft c\u1ee5c b\u1ed9<\/li>\n<\/ul>\n\n\n\n<p><strong>T\u00f9y ch\u1ecdn 2: \u01afu ti\u00ean IPv4<\/strong> m\u00e0 kh\u00f4ng v\u00f4 hi\u1ec7u h\u00f3a ho\u00e0n to\u00e0n IPv6 \u2014 tr\u00ean Linux, ch\u1ec9nh s\u1eeda <code>\/etc\/gai.conf<\/code> v\u00e0 b\u1ecf ch\u00fa th\u00edch <code>precedence ::ffff:0:0\/96 100<\/code>.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"vpn\">B\u01b0\u1edbc 6: Ki\u1ec3m tra VPN, ph\u1ea7n m\u1ec1m di\u1ec7t virus &amp; b\u1ed9 \u0111i\u1ec1u h\u1ee3p Ghost<\/h2>\n\n<h3 class=\"wp-block-heading\" id=\"vpn-and-proxy-dns-interference\">Can thi\u1ec7p DNS c\u1ee7a VPN v\u00e0 Proxy<\/h3>\n\n\n<p>VPN th\u01b0\u1eddng \u0111\u1ecbnh tuy\u1ebfn DNS qua m\u00e1y ch\u1ee7 c\u1ee7a ri\u00eang h\u1ecd, c\u00f3 th\u1ec3 ch\u1eadm h\u01a1n tr\u00ecnh ph\u00e2n gi\u1ea3i c\u1ee5c b\u1ed9 c\u1ee7a b\u1ea1n. M\u1ed9t s\u1ed1 VPN c\u0169ng r\u00f2 r\u1ec9 truy v\u1ea5n DNS ra ngo\u00e0i \u0111\u01b0\u1eddng h\u1ea7m, g\u00e2y ra h\u00e0nh vi kh\u00f4ng nh\u1ea5t qu\u00e1n. \u0110\u1ec3 ch\u1ea9n \u0111o\u00e1n:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Truy c\u1eadp <strong>dnsleaktest.com<\/strong> khi k\u1ebft n\u1ed1i v\u1edbi VPN c\u1ee7a b\u1ea1n \u0111\u1ec3 ki\u1ec3m tra r\u00f2 r\u1ec9 DNS.<\/li>\n\n\n\n<li>T\u1ea1m th\u1eddi ng\u1eaft k\u1ebft n\u1ed1i VPN v\u00e0 ki\u1ec3m tra t\u1ed1c \u0111\u1ed9 DNS. N\u1ebfu nhanh h\u01a1n m\u00e0 kh\u00f4ng c\u00f3 VPN, DNS c\u1ee7a VPN c\u1ee7a b\u1ea1n l\u00e0 n\u00fat th\u1eaft c\u1ed5 chai.<\/li>\n\n\n\n<li>Nhi\u1ec1u VPN cho ph\u00e9p b\u1ea1n c\u1ea5u h\u00ecnh m\u00e1y ch\u1ee7 DNS t\u00f9y ch\u1ec9nh \u2014 s\u1eed d\u1ee5ng Cloudflare ho\u1eb7c Google thay v\u00ec DNS c\u1ee7a nh\u00e0 cung c\u1ea5p VPN.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"antivirus-firewall-dns-filtering\">L\u1ecdc DNS c\u1ee7a ph\u1ea7n m\u1ec1m di\u1ec7t virus \/ T\u01b0\u1eddng l\u1eeda<\/h3>\n\n\n<p>M\u1ed9t s\u1ed1 ph\u1ea7n m\u1ec1m di\u1ec7t virus (Norton, Kaspersky, Bitdefender) ch\u1eb7n v\u00e0 l\u1ecdc truy v\u1ea5n DNS, l\u00e0m t\u0103ng \u0111\u1ed9 tr\u1ec5. T\u01b0\u1eddng l\u1eeda b\u1ea3o m\u1eadt c\u0169ng c\u00f3 th\u1ec3 ch\u1eb7n ho\u1eb7c gi\u1edbi h\u1ea1n l\u01b0u l\u01b0\u1ee3ng DNS \u0111\u1ebfn c\u00e1c m\u00e1y ch\u1ee7 kh\u00f4ng x\u00e1c \u0111\u1ecbnh. \u0110\u1ec3 ki\u1ec3m tra:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>T\u1ea1m th\u1eddi v\u00f4 hi\u1ec7u h\u00f3a b\u1ea3o v\u1ec7 web c\u1ee7a ph\u1ea7n m\u1ec1m di\u1ec7t virus v\u00e0 ki\u1ec3m tra t\u1ed1c \u0111\u1ed9 DNS.<\/li>\n\n\n\n<li>Ki\u1ec3m tra c\u00e1c quy t\u1eafc t\u01b0\u1eddng l\u1eeda c\u1ee7a b\u1ea1n \u0111\u1ec3 xem c\u00f3 b\u1ea5t k\u1ef3 ch\u1eb7n li\u00ean quan \u0111\u1ebfn DNS n\u00e0o (c\u1ed5ng ra 53 ho\u1eb7c 853).<\/li>\n\n\n\n<li>N\u1ebfu DNS nhanh h\u01a1n khi ph\u1ea7n m\u1ec1m di\u1ec7t virus b\u1ecb v\u00f4 hi\u1ec7u h\u00f3a, h\u00e3y th\u00eam ngo\u1ea1i l\u1ec7 cho c\u00e1c m\u00e1y ch\u1ee7 DNS \u01b0a th\u00edch c\u1ee7a b\u1ea1n.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"ghost-network-adapters\">B\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng Ghost<\/h3>\n\n\n<p>C\u00e1c b\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng c\u0169 ho\u1eb7c \u1ea3o t\u1eeb ph\u1ea7n m\u1ec1m VPN, m\u00e1y \u1ea3o (VMware, VirtualBox) ho\u1eb7c Docker c\u00f3 th\u1ec3 gi\u1eef c\u1ea5u h\u00ecnh DNS l\u1ed7i th\u1eddi g\u00e2y c\u1ea3n tr\u1edf vi\u1ec7c ph\u00e2n gi\u1ea3i. Windows \u0111\u1eb7c bi\u1ec7t d\u1ec5 b\u1ecb \u0111i\u1ec1u n\u00e0y.<\/p>\n\n\n\n<p>\u0110\u1ec3 kh\u1eafc ph\u1ee5c tr\u00ean Windows:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>1. Hi\u1ec3n th\u1ecb c\u00e1c thi\u1ebft b\u1ecb \u1ea9n trong Tr\u00ecnh qu\u1ea3n l\u00fd Thi\u1ebft b\u1ecb<br>1. M\u1edf CMD v\u1edbi quy\u1ec1n admin:<br>set devmgr_show_nonpresent_devices=1<br>devmgmt.msc<br><br>1. Trong Tr\u00ecnh qu\u1ea3n l\u00fd Thi\u1ebft b\u1ecb: Xem \u2192 Hi\u1ec3n th\u1ecb c\u00e1c thi\u1ebft b\u1ecb \u1ea9n<br>1. D\u01b0\u1edbi B\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng, x\u00f3a b\u1ea5t k\u1ef3 b\u1ed9 \u0111i\u1ec1u h\u1ee3p \u1ea3o\/\u1ea9n n\u00e0o<\/samp><\/p>\n<\/blockquote>\n\n\n<h2 class=\"wp-block-heading\" id=\"doh\">B\u01b0\u1edbc 7: C\u1ea5u h\u00ecnh DNS qua HTTPS (DoH)<\/h2>\n\n\n<p>DNS qua HTTPS (DoH) m\u00e3 h\u00f3a c\u00e1c truy v\u1ea5n DNS b\u00ean trong HTTPS, ng\u0103n ch\u1eb7n theo d\u00f5i c\u1ee7a ISP, gi\u1ea3 m\u1ea1o DNS v\u00e0 c\u00e1c cu\u1ed9c t\u1ea5n c\u00f4ng man-in-the-middle. Tuy nhi\u00ean, n\u00f3 c\u0169ng c\u00f3 th\u1ec3 g\u00e2y ra v\u1ea5n \u0111\u1ec1 n\u1ebfu c\u1ea5u h\u00ecnh sai.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"benefits\">L\u1ee3i \u00edch<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li>M\u00e3 h\u00f3a l\u01b0u l\u01b0\u1ee3ng DNS \u2014 ISP v\u00e0 qu\u1ea3n tr\u1ecb vi\u00ean m\u1ea1ng kh\u00f4ng th\u1ec3 xem c\u00e1c truy v\u1ea5n DNS c\u1ee7a b\u1ea1n.<\/li>\n\n\n\n<li>Ng\u0103n ch\u1eb7n c\u00e1c cu\u1ed9c t\u1ea5n c\u00f4ng gi\u1ea3 m\u1ea1o DNS v\u00e0 \u0111\u1ea7u \u0111\u1ed9c b\u1ed9 nh\u1edb \u0111\u1ec7m.<\/li>\n\n\n\n<li>S\u1eed d\u1ee5ng c\u1ed5ng 443 (HTTPS ti\u00eau chu\u1ea9n), v\u00ec v\u1eady n\u00f3 hi\u1ebfm khi b\u1ecb t\u01b0\u1eddng l\u1eeda ch\u1eb7n.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"potential-issues\">V\u1ea5n \u0111\u1ec1 ti\u1ec1m \u1ea9n<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u0110\u1ed9 tr\u1ec5 t\u0103ng th\u00eam:<\/strong> B\u1eaft tay HTTPS\/TLS th\u00eam t\u1ea3i cho k\u1ebft n\u1ed1i \u0111\u1ea7u ti\u00ean. C\u00e1c truy v\u1ea5n ti\u1ebfp theo nhanh h\u01a1n do t\u00e1i s\u1eed d\u1ee5ng k\u1ebft n\u1ed1i.<\/li>\n\n\n\n<li><strong>Xung \u0111\u1ed9t v\u1edbi b\u1ed9 l\u1ecdc DNS c\u1ee5c b\u1ed9:<\/strong> DoH b\u1ecf qua Pi-hole, m\u00e1y ch\u1ee7 DNS c\u1ee5c b\u1ed9 v\u00e0 ki\u1ec3m so\u00e1t c\u1ee7a ph\u1ee5 huynh.<\/li>\n\n\n\n<li><strong>Xung \u0111\u1ed9t VPN:<\/strong> DoH c\u00f3 th\u1ec3 \u0111\u1ecbnh tuy\u1ebfn DNS ra ngo\u00e0i \u0111\u01b0\u1eddng h\u1ea7m VPN n\u1ebfu kh\u00f4ng \u0111\u01b0\u1ee3c c\u1ea5u h\u00ecnh \u0111\u00fang.<\/li>\n\n\n\n<li><strong>V\u1ea5n \u0111\u1ec1 DNS chia t\u00e1ch:<\/strong> M\u00f4i tr\u01b0\u1eddng doanh nghi\u1ec7p s\u1eed d\u1ee5ng DNS n\u1ed9i b\u1ed9 cho t\u00e0i nguy\u00ean c\u1ee5c b\u1ed9 c\u00f3 th\u1ec3 b\u1ecb h\u1ecfng khi DoH \u0111\u01b0\u1ee3c b\u1eadt.<\/li>\n\n\n\n<li><strong>Ghi \u0111\u00e8 tr\u00ecnh duy\u1ec7t:<\/strong> Chrome, Firefox v\u00e0 Edge c\u00f3 DoH t\u00edch h\u1ee3p c\u00f3 th\u1ec3 \u00e2m th\u1ea7m ghi \u0111\u00e8 c\u00e0i \u0111\u1eb7t DNS c\u1ee7a h\u1ec7 \u0111i\u1ec1u h\u00e0nh.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"how-to-enable-doh\">C\u00e1ch b\u1eadt DoH<\/h3>\n\n\n<p><strong>Windows 11:<\/strong> C\u00e0i \u0111\u1eb7t \u2192 M\u1ea1ng \u2192 Ethernet\/Wi-Fi \u2192 DNS \u2192 \u0111\u1eb7t \u201cM\u00e3 h\u00f3a DNS \u01b0a th\u00edch\u201d th\u00e0nh \u201cCh\u1ec9 m\u00e3 h\u00f3a (DNS qua HTTPS)\u201d ho\u1eb7c \u201c\u01afu ti\u00ean m\u00e3 h\u00f3a, cho ph\u00e9p kh\u00f4ng m\u00e3 h\u00f3a.\u201d<\/p>\n\n\n\n<p><strong>Chrome\/Edge:<\/strong> C\u00e0i \u0111\u1eb7t \u2192 Quy\u1ec1n ri\u00eang t\u01b0 \u2192 \u201cS\u1eed d\u1ee5ng DNS an to\u00e0n\u201d \u2192 ch\u1ecdn nh\u00e0 cung c\u1ea5p (Cloudflare, Google, v.v.).<\/p>\n\n\n\n<p><strong>Firefox:<\/strong> C\u00e0i \u0111\u1eb7t \u2192 Quy\u1ec1n ri\u00eang t\u01b0 &amp; B\u1ea3o m\u1eadt \u2192 \u201cB\u1eadt DNS qua HTTPS\u201d \u2192 ch\u1ecdn nh\u00e0 cung c\u1ea5p. Firefox m\u1eb7c \u0111\u1ecbnh s\u1eed d\u1ee5ng Cloudflare cho ng\u01b0\u1eddi d\u00f9ng \u1edf M\u1ef9.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"how-to-disable-doh-when-troubleshooting\">C\u00e1ch T\u1eaft DoH (Khi Kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1)<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li>Windows 11: Chuy\u1ec3n m\u00e3 h\u00f3a DNS tr\u1edf l\u1ea1i \u201cCh\u1ec9 kh\u00f4ng m\u00e3 h\u00f3a.\u201d<\/li>\n\n\n\n<li>Chrome\/Edge: Chuy\u1ec3n \u201cS\u1eed d\u1ee5ng DNS an to\u00e0n\u201d sang T\u1eaft.<\/li>\n\n\n\n<li>Firefox: \u0110\u1eb7t th\u00e0nh \u201cT\u1eaft\u201d ho\u1eb7c g\u00f5 <code>about:config<\/code> v\u00e0 \u0111\u1eb7t <code>network.trr.mode = 5<\/code>.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"dns-over-tls-dot-vs-doh\">DNS qua TLS (DoT) vs DoH<\/h3>\n\n\n<p>DoT l\u00e0 m\u1ed9t l\u1ef1a ch\u1ecdn thay th\u1ebf m\u00e3 h\u00f3a DNS tr\u00ean m\u1ed9t c\u1ed5ng chuy\u00ean d\u1ee5ng (853) thay v\u00ec tr\u1ed9n l\u1eabn v\u1edbi l\u01b0u l\u01b0\u1ee3ng HTTPS tr\u00ean c\u1ed5ng 443. DoT d\u1ec5 nh\u1eadn di\u1ec7n v\u00e0 ch\u1eb7n\/qu\u1ea3n l\u00fd tr\u00ean m\u1ea1ng doanh nghi\u1ec7p. DoH h\u00f2a l\u1eabn v\u1edbi l\u01b0u l\u01b0\u1ee3ng web th\u00f4ng th\u01b0\u1eddng, l\u00e0m cho vi\u1ec7c l\u1ecdc kh\u00f3 kh\u0103n h\u01a1n. \u0110\u1ed1i v\u1edbi ng\u01b0\u1eddi d\u00f9ng gia \u0111\u00ecnh, c\u1ea3 hai \u0111\u1ec1u ho\u1ea1t \u0111\u1ed9ng. \u0110\u1ed1i v\u1edbi qu\u1ea3n tr\u1ecb vi\u00ean m\u1ea1ng c\u1ea7n s\u1ef1 r\u00f5 r\u00e0ng, DoT th\u01b0\u1eddng \u0111\u01b0\u1ee3c \u01b0a chu\u1ed9ng.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"local-cache\">B\u01b0\u1edbc 8: Ch\u1ea1y m\u00e1y ch\u1ee7 b\u1ed9 nh\u1edb \u0111\u1ec7m DNS c\u1ee5c b\u1ed9<\/h2>\n\n\n<p>\u0110\u1ed1i v\u1edbi ng\u01b0\u1eddi d\u00f9ng cao c\u1ea5p v\u00e0 qu\u1ea3n tr\u1ecb vi\u00ean m\u1ea1ng, ch\u1ea1y m\u1ed9t b\u1ed9 gi\u1ea3i quy\u1ebft DNS b\u1ed9 nh\u1edb \u0111\u1ec7m c\u1ee5c b\u1ed9 lo\u1ea1i b\u1ecf ho\u00e0n to\u00e0n c\u00e1c chuy\u1ebfn \u0111i v\u00f2ng cho c\u00e1c truy v\u1ea5n l\u1eb7p l\u1ea1i. Thay v\u00ec truy c\u1eadp m\u00e1y ch\u1ee7 DNS t\u1eeb xa m\u1ed7i l\u1ea7n, b\u1ed9 nh\u1edb \u0111\u1ec7m c\u1ee5c b\u1ed9 c\u1ee7a b\u1ea1n ph\u1ea3n h\u1ed3i ngay l\u1eadp t\u1ee9c.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"popular-options\">C\u00e1c L\u1ef1a Ch\u1ecdn Ph\u1ed5 Bi\u1ebfn<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Unbound<\/strong> \u2014 M\u1ed9t b\u1ed9 gi\u1ea3i quy\u1ebft DNS x\u00e1c th\u1ef1c, \u0111\u1ec7 quy, b\u1ed9 nh\u1edb \u0111\u1ec7m. Ng\u0103n ch\u1eb7n b\u1ea5t k\u1ef3 m\u00e1y ch\u1ee7 DNS c\u00f4ng c\u1ed9ng n\u00e0o c\u00f3 t\u1ea5t c\u1ea3 c\u00e1c b\u1ea3n ghi c\u1ee7a b\u1ea1n. H\u1ed7 tr\u1ee3 DoT cho m\u00e3 h\u00f3a ng\u01b0\u1ee3c d\u00f2ng.<\/li>\n\n\n\n<li><strong>dnsmasq<\/strong> \u2014 B\u1ed9 chuy\u1ec3n ti\u1ebfp DNS nh\u1eb9 v\u00e0 m\u00e1y ch\u1ee7 DHCP. D\u1ec5 d\u00e0ng thi\u1ebft l\u1eadp tr\u00ean c\u00e1c b\u1ed9 \u0111\u1ecbnh tuy\u1ebfn Linux.<\/li>\n\n\n\n<li><strong>Pi-hole<\/strong> \u2014 B\u1ed9 ch\u1eb7n qu\u1ea3ng c\u00e1o to\u00e0n m\u1ea1ng c\u0169ng ho\u1ea1t \u0111\u1ed9ng nh\u01b0 m\u1ed9t b\u1ed9 nh\u1edb \u0111\u1ec7m DNS. Ch\u1eb7n qu\u1ea3ng c\u00e1o v\u00e0 tr\u00ecnh theo d\u00f5i \u1edf c\u1ea5p \u0111\u1ed9 DNS, gi\u1ea3m c\u00e1c tra c\u1ee9u DNS c\u1ee7a b\u00ean th\u1ee9 ba cho t\u1ea5t c\u1ea3 c\u00e1c thi\u1ebft b\u1ecb.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"quick-setup-unbound-on-linux\">Thi\u1ebft L\u1eadp Nhanh: Unbound tr\u00ean Linux<\/h3>\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp># C\u00e0i \u0111\u1eb7t Unbound<br>sudo apt c\u00e0i \u0111\u1eb7t unbound<br><br># C\u1ea5u h\u00ecnh c\u01a1 b\u1ea3n: \/etc\/unbound\/unbound.conf<br>m\u00e1y ch\u1ee7:<br>&nbsp;&nbsp;&nbsp;&nbsp;giao di\u1ec7n: 127.0.0.1<br>&nbsp;&nbsp;&nbsp;&nbsp;c\u1ed5ng: 53<br>&nbsp;&nbsp;&nbsp;&nbsp;ki\u1ec3m so\u00e1t truy c\u1eadp: 127.0.0.0\/8 cho ph\u00e9p<br>&nbsp;&nbsp;&nbsp;&nbsp;cache-min-ttl: 300<br>&nbsp;&nbsp;&nbsp;&nbsp;cache-max-ttl: 86400<br>&nbsp;&nbsp;&nbsp;&nbsp;prefetch: c\u00f3<br><br># Chuy\u1ec3n ti\u1ebfp \u0111\u1ebfn Cloudflare qua TLS<br>v\u00f9ng chuy\u1ec3n ti\u1ebfp:<br>&nbsp;&nbsp;&nbsp;&nbsp;t\u00ean: \u201c.\u201d<br>&nbsp;&nbsp;&nbsp;&nbsp;forward-tls-upstream: c\u00f3<br>&nbsp;&nbsp;&nbsp;&nbsp;forward-addr: 1.1.1.1@853<br>&nbsp;&nbsp;&nbsp;&nbsp;forward-addr: 1.0.0.1@853<br><br># Kh\u1edfi \u0111\u1ed9ng v\u00e0 k\u00edch ho\u1ea1t<br>sudo systemctl enable unbound<br>sudo systemctl start unbound<br><br># \u0110\u1eb7t h\u1ec7 th\u1ed1ng c\u1ee7a b\u1ea1n s\u1eed d\u1ee5ng b\u1ed9 gi\u1ea3i quy\u1ebft c\u1ee5c b\u1ed9<br># Ch\u1ec9nh s\u1eeda \/etc\/resolv.conf:<br>nameserver 127.0.0.1<\/samp><\/p>\n<\/blockquote>\n\n\n\n<p>V\u1edbi <code>prefetch: c\u00f3<\/code>, Unbound l\u00e0m m\u1edbi c\u00e1c b\u1ea3n ghi truy c\u1eadp th\u01b0\u1eddng xuy\u00ean tr\u01b0\u1edbc khi ch\u00fang h\u1ebft h\u1ea1n, v\u00ec v\u1eady b\u1ea1n h\u1ea7u nh\u01b0 kh\u00f4ng bao gi\u1edd g\u1eb7p ph\u1ea3i tr\u01b0\u1eddng h\u1ee3p b\u1ed9 nh\u1edb \u0111\u1ec7m l\u1ea1nh.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"browser\">B\u01b0\u1edbc 9: Kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 DNS c\u1ee5 th\u1ec3 c\u1ee7a tr\u00ecnh duy\u1ec7t<\/h2>\n\n\n<p>Tr\u00ecnh duy\u1ec7t c\u00f3 h\u00e0nh vi DNS ri\u00eang c\u1ee7a ch\u00fang c\u00f3 th\u1ec3 ghi \u0111\u00e8 c\u00e0i \u0111\u1eb7t h\u1ec7 \u0111i\u1ec1u h\u00e0nh c\u1ee7a b\u1ea1n:<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"chrome-edge\">Chrome \/ Edge<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li>\u201cDNS An to\u00e0n\u201d t\u00edch h\u1ee3p (DoH) c\u00f3 th\u1ec3 ghi \u0111\u00e8 DNS c\u1ea5p h\u1ec7 \u0111i\u1ec1u h\u00e0nh. Ki\u1ec3m tra: C\u00e0i \u0111\u1eb7t \u2192 Quy\u1ec1n ri\u00eang t\u01b0 \u2192 \u201cS\u1eed d\u1ee5ng DNS an to\u00e0n.\u201d<\/li>\n\n\n\n<li>Chrome duy tr\u00ec b\u1ed9 nh\u1edb \u0111\u1ec7m DNS ri\u00eang c\u1ee7a n\u00f3. X\u00f3a n\u00f3 t\u1ea1i <code>chrome:\/\/net-internals\/#dns<\/code> \u2192 \u201cX\u00f3a b\u1ed9 nh\u1edb \u0111\u1ec7m m\u00e1y ch\u1ee7.\u201d<\/li>\n\n\n\n<li>C\u0169ng x\u00f3a c\u00e1c nh\u00f3m socket: <code>chrome:\/\/net-internals\/#sockets<\/code> \u2192 \u201cX\u00f3a c\u00e1c nh\u00f3m socket.\u201d<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"firefox\">Firefox<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li>Firefox c\u00f3 B\u1ed9 Gi\u1ea3i Quy\u1ebft \u0110\u1ec7 Quy \u0110\u00e1ng Tin C\u1eady (TRR) m\u1eb7c \u0111\u1ecbnh s\u1eed d\u1ee5ng Cloudflare DoH cho ng\u01b0\u1eddi d\u00f9ng \u1edf M\u1ef9. \u0110i\u1ec1u n\u00e0y ho\u00e0n to\u00e0n b\u1ecf qua c\u00e0i \u0111\u1eb7t DNS c\u1ee7a h\u1ec7 \u0111i\u1ec1u h\u00e0nh c\u1ee7a b\u1ea1n.<\/li>\n\n\n\n<li>Ki\u1ec3m tra tr\u1ea1ng th\u00e1i: <code>about:networking#dns<\/code> \u0111\u1ec3 xem c\u00e1c m\u1ee5c DNS \u0111\u01b0\u1ee3c l\u01b0u trong b\u1ed9 nh\u1edb \u0111\u1ec7m v\u00e0 b\u1ed9 gi\u1ea3i quy\u1ebft n\u00e0o \u0111ang ho\u1ea1t \u0111\u1ed9ng.<\/li>\n\n\n\n<li>\u0110\u1ec3 t\u1eaft TRR: C\u00e0i \u0111\u1eb7t \u2192 Quy\u1ec1n ri\u00eang t\u01b0 &amp; B\u1ea3o m\u1eadt \u2192 DNS qua HTTPS \u2192 T\u1eaft.<\/li>\n\n\n\n<li>\u0110\u1ec3 bu\u1ed9c t\u1eaft qua c\u1ea5u h\u00ecnh: <code>about:config<\/code> \u2192 \u0111\u1eb7t <code>network.trr.mode<\/code> \u0110\u1ebeN <code>5<\/code>.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"all-browsers\">T\u1ea5t C\u1ea3 Tr\u00ecnh Duy\u1ec7t<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li>Ti\u1ec7n \u00edch m\u1edf r\u1ed9ng (tr\u00ecnh ch\u1eb7n qu\u1ea3ng c\u00e1o, c\u00f4ng c\u1ee5 b\u1ea3o m\u1eadt) c\u00f3 th\u1ec3 ch\u1eb7n v\u00e0 chuy\u1ec3n h\u01b0\u1edbng DNS. Ki\u1ec3m tra \u1edf ch\u1ebf \u0111\u1ed9 \u1ea9n danh\/ri\u00eang t\u01b0 v\u1edbi c\u00e1c ti\u1ec7n \u00edch m\u1edf r\u1ed9ng b\u1ecb v\u00f4 hi\u1ec7u h\u00f3a.<\/li>\n\n\n\n<li>N\u1ebfu DNS ho\u1ea1t \u0111\u1ed9ng qua <code>\u0111\u00e0o<\/code> ho\u1eb7c <code>nslookup<\/code> nh\u01b0ng tr\u00ecnh duy\u1ec7t ch\u1eadm, v\u1ea5n \u0111\u1ec1 l\u00e0 c\u1ea5p tr\u00ecnh duy\u1ec7t \u2014 kh\u00f4ng ph\u1ea3i DNS h\u1ec7 th\u1ed1ng.<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\" id=\"optimize-records\">B\u01b0\u1edbc 10: T\u1ed1i \u01b0u h\u00f3a b\u1ea3n ghi DNS (Ch\u1ee7 s\u1edf h\u1eefu trang web)<\/h2>\n\n\n<p>N\u1ebfu b\u1ea1n qu\u1ea3n l\u00fd m\u1ed9t trang web v\u00e0 DNS c\u1ee7a n\u00f3 ch\u1eadm \u0111\u1ed1i v\u1edbi kh\u00e1ch truy c\u1eadp, c\u00e1c t\u1ed1i \u01b0u h\u00f3a n\u00e0y \u00e1p d\u1ee5ng:<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"reduce-and-clean-up-records\">Gi\u1ea3m v\u00e0 D\u1ecdn D\u1eb9p B\u1ea3n Ghi<\/h3>\n\n\n<p>Lo\u1ea1i b\u1ecf c\u00e1c b\u1ea3n ghi A, CNAME, TXT v\u00e0 MX kh\u00f4ng s\u1eed d\u1ee5ng. M\u1ed7i b\u1ea3n ghi th\u00eam v\u00e0o t\u0103ng th\u00eam chi ph\u00ed trong qu\u00e1 tr\u00ecnh gi\u1ea3i quy\u1ebft. Ki\u1ec3m tra t\u1ec7p v\u00f9ng DNS c\u1ee7a b\u1ea1n h\u00e0ng qu\u00fd.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"eliminate-cname-chaining\">Lo\u1ea1i B\u1ecf Chu\u1ed7i CNAME<\/h3>\n\n\n<p>Thay v\u00ec CNAME \u2192 CNAME \u2192 b\u1ea3n ghi A, h\u00e3y tr\u1ecf c\u00e1c mi\u1ec1n tr\u1ef1c ti\u1ebfp \u0111\u1ebfn IP cu\u1ed1i c\u00f9ng qua m\u1ed9t b\u1ea3n ghi A. Nhi\u1ec1u nh\u00e0 cung c\u1ea5p DNS c\u0169ng h\u1ed7 tr\u1ee3 <strong>l\u00e0m ph\u1eb3ng CNAME<\/strong> (c\u00f2n g\u1ecdi l\u00e0 b\u1ea3n ghi ALIAS), gi\u1ea3i quy\u1ebft chu\u1ed7i ph\u00eda m\u00e1y ch\u1ee7 v\u00e0 tr\u1ea3 v\u1ec1 IP trong m\u1ed9t truy v\u1ea5n duy nh\u1ea5t.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"set-appropriate-ttl-values\">\u0110\u1eb7t Gi\u00e1 Tr\u1ecb TTL Ph\u00f9 H\u1ee3p<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li><strong>B\u1ea3n ghi \u1ed5n \u0111\u1ecbnh:<\/strong> S\u1eed d\u1ee5ng TTL cao h\u01a1n (3600\u201386400 gi\u00e2y) \u0111\u1ec3 t\u1ed1i \u0111a h\u00f3a l\u1ee3i \u00edch b\u1ed9 nh\u1edb \u0111\u1ec7m.<\/li>\n\n\n\n<li><strong>B\u1ea3n ghi thay \u0111\u1ed5i th\u01b0\u1eddng xuy\u00ean:<\/strong> S\u1eed d\u1ee5ng TTL t\u1eeb 300\u2013600 gi\u00e2y (5\u201310 ph\u00fat).<\/li>\n\n\n\n<li>Tr\u00e1nh \u0111\u1eb7t TTL th\u00e0nh 86400 (24 gi\u1edd) tr\u1eeb khi b\u1ea3n ghi th\u1ef1c s\u1ef1 kh\u00f4ng bao gi\u1edd thay \u0111\u1ed5i, v\u00ec \u0111i\u1ec1u n\u00e0y l\u00e0m ch\u1eadm s\u1ef1 lan truy\u1ec1n c\u1ee7a c\u00e1c c\u1eadp nh\u1eadt.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"dnssec-considerations\">C\u00e2n Nh\u1eafc DNSSEC<\/h3>\n\n\n<p>DNSSEC th\u00eam x\u00e1c minh ch\u1eef k\u00fd m\u00e3 h\u00f3a v\u00e0o c\u00e1c ph\u1ea3n h\u1ed3i DNS, ng\u0103n ch\u1eb7n nhi\u1ec5m \u0111\u1ed9c b\u1ed9 nh\u1edb \u0111\u1ec7m v\u00e0 gi\u1ea3 m\u1ea1o. Tuy nhi\u00ean, n\u00f3 th\u00eam th\u1eddi gian x\u1eed l\u00fd cho m\u1ed7i tra c\u1ee9u. S\u1ef1 \u0111\u00e1nh \u0111\u1ed5i l\u00e0 t\u0103ng \u0111\u1ed9 tr\u1ec5 nh\u1ecf \u0111\u1ec3 c\u00f3 b\u1ea3o m\u1eadt t\u1ed1t h\u01a1n \u0111\u00e1ng k\u1ec3. B\u1eadt DNSSEC n\u1ebfu b\u1ea3o m\u1eadt l\u00e0 \u01b0u ti\u00ean; h\u00e3y l\u01b0u \u00fd r\u1eb1ng n\u00f3 c\u00f3 th\u1ec3 t\u0103ng th\u1eddi gian gi\u1ea3i quy\u1ebft m\u1ed9t ch\u00fat, \u0111\u1eb7c bi\u1ec7t tr\u00ean c\u00e1c m\u00e1y ch\u1ee7 t\u00ean c\u00f3 th\u1ea9m quy\u1ec1n ch\u1eadm h\u01a1n.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"use-a-premium-dns-provider-cdn\">S\u1eed D\u1ee5ng Nh\u00e0 Cung C\u1ea5p DNS Cao C\u1ea5p \/ CDN<\/h3>\n\n\n<p>DNS mi\u1ec5n ph\u00ed t\u1eeb c\u00e1c nh\u00e0 \u0111\u0103ng k\u00fd t\u00ean mi\u1ec1n th\u01b0\u1eddng ch\u1eadm. C\u00e1c nh\u00e0 cung c\u1ea5p DNS cao c\u1ea5p (Cloudflare, AWS Route 53, Dyn, DNS Made Easy) c\u00f3 c\u01a1 s\u1edf h\u1ea1 t\u1ea7ng anycast ph\u00e2n ph\u1ed1i to\u00e0n c\u1ea7u l\u1edbn \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf cho c\u00e1c ph\u1ea3n h\u1ed3i \u0111\u1ed9 tr\u1ec5 th\u1ea5p. CDN nh\u01b0 Cloudflare ho\u1eb7c Akamai c\u00f3 c\u01a1 s\u1edf h\u1ea1 t\u1ea7ng DNS ri\u00eang v\u1edbi c\u00e1c \u0111i\u1ec3m hi\u1ec7n di\u1ec7n ph\u00e2n ph\u1ed1i to\u00e0n c\u1ea7u, c\u1eaft gi\u1ea3m th\u1eddi gian tra c\u1ee9u cho ng\u01b0\u1eddi d\u00f9ng tr\u00ean to\u00e0n th\u1ebf gi\u1edbi.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"reduce-domains\">B\u01b0\u1edbc 11: Gi\u1ea3m c\u00e1c mi\u1ec1n c\u1ee7a b\u00ean th\u1ee9 ba (Ch\u1ee7 s\u1edf h\u1eefu trang web)<\/h2>\n\n\n<p>M\u1ed7i mi\u1ec1n b\u00ean th\u1ee9 ba duy nh\u1ea5t m\u00e0 trang web c\u1ee7a b\u1ea1n t\u1ea3i y\u00eau c\u1ea7u m\u1ed9t tra c\u1ee9u DNS ri\u00eang bi\u1ec7t. Nh\u1eefng \u0111i\u1ec1u n\u00e0y c\u1ed9ng l\u1ea1i nhanh ch\u00f3ng \u2014 m\u1ed9t trang t\u1ea3i t\u00e0i nguy\u00ean t\u1eeb 7 mi\u1ec1n b\u00ean ngo\u00e0i c\u00f3 th\u1ec3 t\u00edch l\u0169y h\u01a1n 1 gi\u00e2y th\u1eddi gian DNS ch\u1ec9 ri\u00eang.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"how-to-reduce\">C\u00e1ch Gi\u1ea3m<\/h3>\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ki\u1ec3m tra t\u00e0i nguy\u00ean b\u00ean ngo\u00e0i:<\/strong> S\u1eed d\u1ee5ng DevTools c\u1ee7a tr\u00ecnh duy\u1ec7t (tab M\u1ea1ng) ho\u1eb7c WebPageTest \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh m\u1ecdi mi\u1ec1n duy nh\u1ea5t m\u00e0 trang web c\u1ee7a b\u1ea1n g\u1ecdi.<\/li>\n\n\n\n<li><strong>T\u1ef1 l\u01b0u tr\u1eef n\u1ebfu c\u00f3 th\u1ec3:<\/strong> T\u1ea3i xu\u1ed1ng ph\u00f4ng ch\u1eef, t\u1eadp l\u1ec7nh v\u00e0 t\u00e0i s\u1ea3n c\u1ee7a b\u00ean th\u1ee9 ba v\u00e0 l\u01b0u tr\u1eef ch\u00fang tr\u00ean m\u00e1y ch\u1ee7 g\u1ed1c c\u1ee7a b\u1ea1n ho\u1eb7c CDN. \u0110i\u1ec1u n\u00e0y lo\u1ea1i b\u1ecf ho\u00e0n to\u00e0n c\u00e1c tra c\u1ee9u DNS c\u1ee7a ch\u00fang.<\/li>\n\n\n\n<li><strong>H\u1ee3p nh\u1ea5t c\u00e1c mi\u1ec1n CDN:<\/strong> S\u1eed d\u1ee5ng m\u1ed9t mi\u1ec1n ph\u1ee5 CDN duy nh\u1ea5t thay v\u00ec nhi\u1ec1u m\u00e1y ch\u1ee7 b\u00ean ngo\u00e0i.<\/li>\n\n\n\n<li><strong>Lo\u1ea1i b\u1ecf c\u00e1c plugin v\u00e0 tr\u00ecnh theo d\u00f5i kh\u00f4ng s\u1eed d\u1ee5ng:<\/strong> M\u1ed7i plugin t\u1ea3i JavaScript b\u00ean ngo\u00e0i th\u00eam \u00edt nh\u1ea5t m\u1ed9t tra c\u1ee9u DNS c\u1ed9ng v\u1edbi ch\u00ednh t\u1eadp l\u1ec7nh.<\/li>\n<\/ul>\n\n\n<h3 class=\"wp-block-heading\" id=\"defer-noncritical-javascript\">Tr\u00ec Ho\u00e3n JavaScript Kh\u00f4ng Quan Tr\u1ecdng<\/h3>\n\n\n<p>JavaScript c\u1ee7a b\u00ean th\u1ee9 ba th\u01b0\u1eddng t\u1ea3i th\u00eam c\u00e1c mi\u1ec1n b\u00ean ngo\u00e0i. Tr\u00ec ho\u00e3n JS kh\u00f4ng quan tr\u1ecdng tr\u00ec ho\u00e3n c\u00e1c tra c\u1ee9u DNS \u0111\u00f3 cho \u0111\u1ebfn sau khi trang ch\u00ednh \u0111\u01b0\u1ee3c hi\u1ec3n th\u1ecb:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>&lt;!&#8211; Defer non-critical third-party scripts &#8211;&gt;<br>&lt;script src=&#8221;https:\/\/analytics.example.com\/tracker.js&#8221; defer&gt;&lt;\/script&gt;<br><br>&lt;!&#8211; Async for scripts that don&#8217;t depend on page load order &#8211;&gt;<br>&lt;script src=&#8221;https:\/\/ads.example.com\/ad.js&#8221; async&gt;&lt;\/script&gt;<\/samp><\/p>\n<\/blockquote>\n\n\n\n<p>S\u1eed d\u1ee5ng <code>tr\u00ec ho\u00e3n<\/code> ho\u1eb7c <code>b\u1ea5t \u0111\u1ed3ng b\u1ed9<\/code> ng\u0103n c\u00e1c t\u1eadp l\u1ec7nh n\u00e0y ch\u1eb7n vi\u1ec7c hi\u1ec3n th\u1ecb trang ch\u00ednh trong khi v\u1eabn t\u1ea3i ch\u00fang. C\u00e1c tra c\u1ee9u DNS cho c\u00e1c mi\u1ec1n n\u00e0y v\u1eabn x\u1ea3y ra, nh\u01b0ng ch\u00fang kh\u00f4ng c\u00f2n ch\u1eb7n ng\u01b0\u1eddi d\u00f9ng xem n\u1ed9i dung.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"prefetch\">B\u01b0\u1edbc 12: Th\u1ef1c hi\u1ec7n DNS Prefetching (Nh\u00e0 ph\u00e1t tri\u1ec3n web)<\/h2>\n\n\n<p>C\u00e1c tr\u00ecnh duy\u1ec7t hi\u1ec7n \u0111\u1ea1i h\u1ed7 tr\u1ee3 <code>dns-prefetch<\/code> V\u00e0 <code>preconnect<\/code> g\u1ee3i \u00fd t\u00e0i nguy\u00ean gi\u1ea3i quy\u1ebft DNS cho c\u00e1c mi\u1ec1n b\u00ean th\u1ee9 ba tr\u01b0\u1edbc khi ng\u01b0\u1eddi d\u00f9ng c\u1ea7n ch\u00fang:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><samp>&lt;!&#8211; DNS prefetch for non-critical third-party domains &#8211;&gt;<br>&lt;link rel=&#8221;dns-prefetch&#8221; href=&#8221;https:\/\/fonts.googleapis.com&#8221;&gt;<br>&lt;link rel=&#8221;dns-prefetch&#8221; href=&#8221;https:\/\/analytics.example.com&#8221;&gt;<br><br>&lt;!&#8211; Preconnect for critical third-party domains (DNS + TCP + TLS) &#8211;&gt;<br>&lt;link rel=&#8221;preconnect&#8221; href=&#8221;https:\/\/cdn.example.com&#8221;&gt;<br>&lt;link rel=&#8221;preconnect&#8221; href=&#8221;https:\/\/api.example.com&#8221;&gt;<\/samp><\/p>\n<\/blockquote>\n\n\n\n<p>S\u1eed d\u1ee5ng <code>preconnect<\/code> cho c\u00e1c k\u1ebft n\u1ed1i quan tr\u1ecdng nh\u1ea5t c\u1ee7a b\u1ea1n (n\u00f3 x\u1eed l\u00fd DNS + TCP + TLS) v\u00e0 <code>dns-prefetch<\/code> cho m\u1ecdi th\u1ee9 kh\u00e1c. Preconnect c\u00f3 th\u1ec3 ti\u1ebft ki\u1ec7m 100\u2013500 ms m\u1ed7i k\u1ebft n\u1ed1i, trong khi DNS prefetch ti\u1ebft ki\u1ec7m 20\u2013120 ms. \u0110\u1eebng l\u1ea1m d\u1ee5ng preconnect \u2014 m\u1ed7i c\u00e1i m\u1edf m\u1ed9t k\u1ebft n\u1ed1i ti\u00eau t\u1ed1n t\u00e0i nguy\u00ean.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n<h2 class=\"wp-block-heading\" id=\"troubleshooting\">B\u1ea3ng tham kh\u1ea3o nhanh v\u1ec1 kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1<\/h2>\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th>Tri\u1ec7u Ch\u1ee9ng<\/th><th>Nguy\u00ean Nh\u00e2n C\u00f3 Th\u1ec3<\/th><th>Kh\u1eafc Ph\u1ee5c<\/th><\/tr><tr><td>T\u1ea5t c\u1ea3 c\u00e1c trang t\u1ea3i ch\u1eadm trong l\u1ea7n truy c\u1eadp \u0111\u1ea7u ti\u00ean<\/td><td>B\u1ed9 gi\u1ea3i quy\u1ebft DNS c\u1ee7a ISP ch\u1eadm<\/td><td>Chuy\u1ec3n sang Cloudflare (1.1.1.1) ho\u1eb7c Google (8.8.8.8). Kh\u1edfi \u0111\u1ed9ng l\u1ea1i b\u1ed9 \u0111\u1ecbnh tuy\u1ebfn tr\u01b0\u1edbc.<\/td><\/tr><tr><td>Tr\u1ec5 5 gi\u00e2y tr\u01b0\u1edbc khi trang b\u1eaft \u0111\u1ea7u t\u1ea3i<\/td><td>\u0110\u1ed9 tr\u1ec5 d\u1ef1 ph\u00f2ng IPv6<\/td><td>T\u1eaft IPv6 tr\u00ean b\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng ho\u1eb7c \u0111\u1eb7t h\u1ec7 \u0111i\u1ec1u h\u00e0nh \u01b0u ti\u00ean IPv4.<\/td><\/tr><tr><td>Mi\u1ec1n c\u1ee5 th\u1ec3 kh\u00f4ng gi\u1ea3i quy\u1ebft \u0111\u01b0\u1ee3c<\/td><td>B\u1ed9 nh\u1edb \u0111\u1ec7m DNS c\u0169<\/td><td>X\u00f3a b\u1ed9 nh\u1edb \u0111\u1ec7m DNS tr\u00ean h\u1ec7 \u0111i\u1ec1u h\u00e0nh v\u00e0 tr\u00ecnh duy\u1ec7t.<\/td><\/tr><tr><td>DNS ho\u1ea1t \u0111\u1ed9ng trong terminal nh\u01b0ng tr\u00ecnh duy\u1ec7t ch\u1eadm<\/td><td>Ghi \u0111\u00e8 DoH c\u1ee7a tr\u00ecnh duy\u1ec7t ho\u1eb7c can thi\u1ec7p ti\u1ec7n \u00edch m\u1edf r\u1ed9ng<\/td><td>Ki\u1ec3m tra c\u00e0i \u0111\u1eb7t DNS an to\u00e0n c\u1ee7a Chrome\/Firefox. Ki\u1ec3m tra \u1edf ch\u1ebf \u0111\u1ed9 \u1ea9n danh v\u1edbi c\u00e1c ti\u1ec7n \u00edch m\u1edf r\u1ed9ng b\u1ecb v\u00f4 hi\u1ec7u h\u00f3a.<\/td><\/tr><tr><td>DNS ch\u1eadm ch\u1ec9 khi VPN \u0111\u01b0\u1ee3c k\u1ebft n\u1ed1i<\/td><td>\u0110\u1ecbnh tuy\u1ebfn DNS c\u1ee7a VPN<\/td><td>C\u1ea5u h\u00ecnh DNS t\u00f9y ch\u1ec9nh trong c\u00e0i \u0111\u1eb7t VPN ho\u1eb7c ki\u1ec3m tra r\u00f2 r\u1ec9 DNS t\u1ea1i dnsleaktest.com.<\/td><\/tr><tr><td>DNS ch\u1eadm kh\u00f4ng li\u00ean t\u1ee5c v\u1edbi ph\u1ea7n m\u1ec1m di\u1ec7t virus \u0111ang ch\u1ea1y<\/td><td>L\u1ecdc DNS c\u1ee7a ph\u1ea7n m\u1ec1m di\u1ec7t virus<\/td><td>T\u1ea1m th\u1eddi v\u00f4 hi\u1ec7u h\u00f3a b\u1ea3o v\u1ec7 web. Th\u00eam ngo\u1ea1i l\u1ec7 m\u00e1y ch\u1ee7 DNS n\u1ebfu nhanh h\u01a1n.<\/td><\/tr><tr><td>dig +trace cho th\u1ea5y m\u1ed9t b\u01b0\u1edbc nh\u1ea3y m\u1ea5t &gt;200 ms<\/td><td>M\u00e1y ch\u1ee7 t\u00ean c\u00f3 th\u1ea9m quy\u1ec1n ch\u1eadm<\/td><td>Chuy\u1ec3n sang nh\u00e0 cung c\u1ea5p DNS v\u1edbi ki\u1ebfn tr\u00fac CDN ho\u1eb7c s\u1eed d\u1ee5ng l\u00e0m ph\u1eb3ng CNAME.<\/td><\/tr><tr><td>Th\u1eddi gian DNS cao trong PageSpeed \/ WebPageTest<\/td><td>Qu\u00e1 nhi\u1ec1u mi\u1ec1n c\u1ee7a b\u00ean th\u1ee9 ba<\/td><td>Th\u00eam g\u1ee3i \u00fd dns-prefetch \/ preconnect. Gi\u1ea3m c\u00e1c mi\u1ec1n b\u00ean ngo\u00e0i. Tr\u00ec ho\u00e3n JS kh\u00f4ng quan tr\u1ecdng.<\/td><\/tr><tr><td>DNS ho\u1ea1t \u0111\u1ed9ng nh\u01b0ng ch\u1eadm kh\u00f4ng li\u00ean t\u1ee5c<\/td><td>M\u00e1y ch\u1ee7 t\u00ean qu\u00e1 t\u1ea3i ho\u1eb7c b\u1ed9 \u0111i\u1ec1u h\u1ee3p ma<\/td><td>\u0110\u00e1nh gi\u00e1 v\u1edbi GRC DNS Benchmark. Lo\u1ea1i b\u1ecf b\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng ma. C\u00e2n nh\u1eafc DNS th\u1ee9 c\u1ea5p.<\/td><\/tr><tr><td>DNS ch\u1eadm ch\u1ec9 t\u1eeb m\u1ed9t s\u1ed1 khu v\u1ef1c<\/td><td>Kho\u1ea3ng c\u00e1ch \u0111\u1ecba l\u00fd<\/td><td>S\u1eed d\u1ee5ng nh\u00e0 cung c\u1ea5p DNS v\u1edbi anycast to\u00e0n c\u1ea7u (Cloudflare, Route 53).<\/td><\/tr><tr><td>Mi\u1ec1n m\u1ea1ng c\u1ee5c b\u1ed9 kh\u00f4ng gi\u1ea3i quy\u1ebft \u0111\u01b0\u1ee3c v\u1edbi DoH b\u1eadt<\/td><td>DoH b\u1ecf qua DNS c\u1ee5c b\u1ed9<\/td><td>T\u1eaft DoH trong tr\u00ecnh duy\u1ec7t ho\u1eb7c c\u1ea5u h\u00ecnh DNS chia t\u00e1ch. S\u1eed d\u1ee5ng DoT thay th\u1ebf cho doanh nghi\u1ec7p.<\/td><\/tr><tr><td>Trang ch\u1eadm sau khi c\u00e0i \u0111\u1eb7t ph\u1ea7n m\u1ec1m g\u1ea7n \u0111\u00e2y<\/td><td>VPN\/VM m\u1edbi th\u00eam b\u1ed9 \u0111i\u1ec1u h\u1ee3p m\u1ea1ng ma<\/td><td>Ki\u1ec3m tra Tr\u00ecnh Qu\u1ea3n L\u00fd Thi\u1ebft B\u1ecb \u0111\u1ec3 t\u00ecm b\u1ed9 \u0111i\u1ec1u h\u1ee3p ma. Lo\u1ea1i b\u1ecf c\u1ea5u h\u00ecnh DNS c\u0169.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><\/p>","protected":false},"excerpt":{"rendered":"<p>Tra c\u1ee9u DNS ch\u1eadm l\u00e0m t\u0103ng \u0111\u1ed9 tr\u1ec5 kh\u00f4ng c\u1ea7n thi\u1ebft tr\u01b0\u1edbc khi tr\u00ecnh duy\u1ec7t c\u1ee7a b\u1ea1n th\u1eadm ch\u00ed b\u1eaft \u0111\u1ea7u t\u1ea3i m\u1ed9t trang web. M\u1ed9t qu\u00e1 tr\u00ecnh gi\u1ea3i quy\u1ebft DNS \u0111i\u1ec3n h\u00ecnh m\u1ea5t 20\u2013120 ms, nh\u01b0ng DNS \u0111\u01b0\u1ee3c c\u1ea5u h\u00ecnh sai ho\u1eb7c ho\u1ea1t \u0111\u1ed9ng k\u00e9m c\u00f3 th\u1ec3 \u0111\u1ea9y \u0111i\u1ec1u \u0111\u00f3 l\u00ean\u2026 <a class=\"more-link\" href=\"https:\/\/securitybriefing.net\/vi\/cong-nghe\/cach-khac-phuc-tra-cuu-dns-cham\/\">Ti\u1ebfp t\u1ee5c \u0111\u1ecdc <span class=\"screen-reader-text\">C\u00e1ch Kh\u1eafc Ph\u1ee5c Tra C\u1ee9u DNS Ch\u1eadm<\/span><\/a><\/p>","protected":false},"author":3,"featured_media":5248,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[30],"tags":[],"class_list":["post-5245","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tech","entry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>How to Fix Slow DNS Lookup: 12-Step Diagnostic &amp; Fix<\/title>\n<meta name=\"description\" content=\"How to fix slow DNS lookup in 12 steps. Covers dig, nslookup, IPv6 fallback, DoH, VPN conflicts, local caching, browser overrides, and DNS prefetching with code.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/securitybriefing.net\/vi\/cong-nghe\/cach-khac-phuc-tra-cuu-dns-cham\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How to Fix Slow DNS Lookup: 12-Step Diagnostic &amp; Fix\" \/>\n<meta property=\"og:description\" content=\"How to fix slow DNS lookup in 12 steps. 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