{"id":573,"date":"2018-07-02T12:05:47","date_gmt":"2018-07-02T05:05:47","guid":{"rendered":"https:\/\/lagonet.vn\/?p=573"},"modified":"2018-07-02T12:05:47","modified_gmt":"2018-07-02T05:05:47","slug":"spanning-tree-va-cach-no-chong-loop","status":"publish","type":"post","link":"https:\/\/kb.lagonet.vn\/?p=573","title":{"rendered":"SPANNING TREE V\u00c0 C\u00c1CH N\u00d3 CH\u1ed0NG LOOP"},"content":{"rendered":"<figure id=\"attachment_574\" aria-describedby=\"caption-attachment-574\" style=\"width: 494px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-574\" src=\"https:\/\/lagonet.vn\/wp-content\/uploads\/2018\/07\/spanningtree-01.jpg\" alt=\"spanningtree-01\" width=\"494\" height=\"266\" \/><figcaption id=\"caption-attachment-574\" class=\"wp-caption-text\">V\u00ed d\u1ee5 Spanning Tree<\/figcaption><\/figure>\n<p>Spanning Tree l\u00e0 giao th\u1ee9c ch\u1ed1ng loop tr\u00ean c\u00e1c thi\u1ebft b\u1ecb m\u1ea1ng (802.1d).<\/p>\n<p>N\u00f3 s\u1eed d\u1ee5ng BPDU packets \u0111\u1ec3 giao ti\u1ebfp v\u1edbi c\u00e1c switch kh\u00e1c nh\u1eb1m t\u00ecm ra c\u1ed5ng block \u0111\u1ec3 ng\u0103n ch\u1eb7n vi\u1ec7c b\u1ecb loop trong h\u1ec7 th\u1ed1ng m\u1ea1ng ng\u00e0y nay.<\/p>\n<p>&nbsp;<\/p>\n<p>C\u00e1ch Spanning Tree ho\u1ea1t \u0111\u1ed9ng th\u1ebf n\u00e0o?<\/p>\n<p>C\u00e1c switch s\u1ebd b\u1ea7u ch\u1ecdn ai l\u00e0 root switch v\u1edbi m\u1ed9t thi\u1ebft b\u1ecb m\u1edbi mua, ch\u01b0a config g\u00ec c\u1ea3.<\/p>\n<p>Qu\u00e1 tr\u00ecnh n\u00e0y s\u1eed d\u1ee5ng Bridge-ID (8 bytes) vi\u1ebft t\u1eaft l\u00e0 BID, BID n\u00e0o th\u1ea5p nh\u1ea5t th\u00ec s\u1ebd l\u00e0 root switch.<\/p>\n<p>BID bao g\u1ed3m 2 bytes:<\/p>\n<ul>\n<li>Priority (2 bytes): 0 &#8211; 65535 (default 32768)<\/li>\n<li>MAC (6 bytes)<\/li>\n<\/ul>\n<p>V\u1eady l\u00e0m sao \u0111\u1ec3 bi\u1ebft switch n\u00e0o c\u00f3 \u0111\u1ecba ch\u1ec9 MAC nh\u1ecf h\u01a1n?<\/p>\n<p>VD:<\/p>\n<ul>\n<li>A: 0010.5a0c.fd86<\/li>\n<li>B: 0010.5a0c.fd87<\/li>\n<li>C: 0010.6000.0000<\/li>\n<\/ul>\n<p>=&gt; A &lt; B &lt; C<\/p>\n<p>=&gt; Root switch s\u1ebd l\u00e0 A<\/p>\n<p>Ta s\u1ebd x\u00e9t v\u00ed d\u1ee5 tr\u00ean, v\u00ed d\u1ee5 A &lt; B &lt; C &lt; D th\u00ec \u0111i\u1ec1u g\u00ec s\u1ebd x\u1ea3y ra v\u1edbi 4 con switch \u0111\u00f3?<\/p>\n<p>B1: ch\u1ecdn Root switch<\/p>\n<ul>\n<li>A s\u1ebd l\u00e0 root switch<\/li>\n<li>A s\u1ebd \u0111\u1ecbnh k\u1ef3 g\u1eedi BPDU m\u1ed7i 2s\/l\u1ea7n<\/li>\n<li>C\u00e1c switch BCD ch\u1ec9 forward BPDU c\u1ee7a root switch<\/li>\n<\/ul>\n<p>B2: B\u1ea7u ch\u1ecdn root port<\/p>\n<p>Tr\u00ean t\u1ea5t c\u1ea3 non-rootswitch ph\u1ea3i ch\u1ecdn ra 1 root port m\u00e0 cung c\u1ea5p \u0111\u01b0\u1eddng v\u1ec1 root switch m\u00e0 \u0111\u01b0\u1eddng nh\u1ecf nh\u1ea5t cho con switch \u0111ang x\u00e9t<\/p>\n<p>ta c\u00f3 b\u1ea3ng quy \u0111\u1ed5i cost nh\u01b0 sau:<\/p>\n<table>\n<tbody>\n<tr>\n<td style=\"text-align: center;\" width=\"312\">\n<h2><strong>Bandwidth<\/strong><\/h2>\n<\/td>\n<td style=\"text-align: center;\" width=\"312\">\n<h2><strong>Cost<\/strong><\/h2>\n<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"312\">10 Mbps<\/td>\n<td style=\"text-align: center;\" width=\"312\">100<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"312\">100 Mbps<\/td>\n<td style=\"text-align: center;\" width=\"312\">19<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"312\">1 Gbps<\/td>\n<td style=\"text-align: center;\" width=\"312\">4<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: center;\" width=\"312\">10 Gbps<\/td>\n<td style=\"text-align: center;\" width=\"312\">2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n<p>Ta v\u00ed d\u1ee5 t\u1ea5t c\u1ea3 c\u00e1c c\u1ed5ng c\u00f3 cost \u0111\u1ec1u l\u00e0 = 19, th\u00ec sao?<\/p>\n<p>Mu\u1ed1n t\u1ed5ng path cost t\u1eeb 1 c\u1ed5ng n\u00e0o v\u1ec1 root switch th\u00ec ta t\u00ednh t\u1ed5ng t\u1eeb root switch t\u00ednh v\u1ec1 (\u0111i v\u00e0o th\u00ec c\u1ed9ng, \u0111i ra th\u00ec kh\u00f4ng c\u1ed9ng)<\/p>\n<ul>\n<li>X\u00e9t D, eth0\/0 = 19, eth0\/1 = 57 =&gt; eth0\/0 l\u00e0 root port<\/li>\n<li>X\u00e9t B, eth0\/0 = 19, eth0\/1 = 57 =&gt; eth0\/0 l\u00e0 root port<\/li>\n<li>X\u00e9t C,\u00a0eth0\/0 = 38, eth0\/1 = 38\n<ul>\n<li>ta x\u00e9t Tie-Breaker cho path cost: Sender B-ID<\/li>\n<li>c\u1ed5ng n\u00e0o n\u1ed1i v\u1edbi switch l\u00e1ng gi\u1ec1ng c\u00f3 BID nh\u1ecf h\u01a1n th\u00ec s\u1ebd tr\u1edf th\u00e0nh root port<\/li>\n<li>=&gt; c\u1ed5ng n\u1ed1i v\u1edbi D l\u00e0 root port =&gt; eth0\/1<\/li>\n<\/ul>\n<\/li>\n<li>V\u00ed d\u1ee5 ta c\u00f3 2 link gi\u1ed1ng nhau n\u1ed1i th\u00eam v\u00e0o C v\u00e0 D d\u1eabn \u0111\u1ebfn t\u1eeb C \u0111\u1ebfn root lu\u00f4n = 38\n<ul>\n<li>S\u1eed d\u1ee5ng Port ID (Port Priority + Port number) gi\u1eefa C v\u00e0 D.<\/li>\n<li>C\u1ed5ng n\u00e0o PortID nh\u1ecf h\u01a1n s\u1ebd th\u00e0nh root port<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>B3: B\u1ea7u ch\u1ecdn Designated port<\/p>\n<p>L\u00e0 port cung c\u1ea5p \u0111\u01b0\u1eddng v\u1ec1 root switch cho ph\u00e2n \u0111o\u1ea1n m\u1ea1ng (kh\u00f4ng ph\u1ea3i cho con switch) m\u00e0 c\u00f3 t\u1ed5ng path cost nh\u1ecf nh\u1ea5t.<\/p>\n<p>Quy t\u1eafc c\u1ea7n ch\u00fa \u00fd:<\/p>\n<ul>\n<li>T\u1ea5t c\u1ea3 c\u00e1c c\u1ed5ng c\u1ee7a root switch \u0111\u1ec1u l\u00e0 designated port<\/li>\n<li>C\u1ed5ng \u0111\u1ea5u n\u1ed1i v\u1edbi root port s\u1ebd ph\u1ea3i l\u00e0 designated port<\/li>\n<li>Designated port\u00a0cung c\u1ea5p \u0111\u01b0\u1eddng v\u1ec1 root switch cho ph\u00e2n \u0111o\u1ea1n m\u1ea1ng (kh\u00f4ng ph\u1ea3i cho con switch) m\u00e0 c\u00f3 t\u1ed5ng path cost nh\u1ecf nh\u1ea5t<\/li>\n<\/ul>\n<p>\u00c1p d\u1ee5ng v\u00ed d\u1ee5 tr\u00eanm ta t\u00ednh \u0111\u01b0\u1ee3c c\u1ed5ng eth0\/0 s\u1ebd b\u1ecb block (kh\u00f3a)<\/p>\n<p>B4: Blocking port<\/p>\n<hr \/>\n<p>STP timers:<\/p>\n<ul>\n<li>Hello timer: 2s<\/li>\n<li>Forward delay timer: 15s<\/li>\n<li>Max age timer: 20s<\/li>\n<\/ul>\n<p>STP port states:<\/p>\n<ul>\n<li>Disabled: coi nh\u01b0 c\u1ed5ng b\u1ecb shutdown<\/li>\n<li>Blocking: 1 port ch\u1ec9 \u0111\u01b0\u1ee3c quy\u1ec1n nh\u1eadn BPDU, kh\u00f4ng g\u1eedi BPDU, kh\u00f4ng \u0111\u01b0\u1ee3c h\u1ecdc MAC n\u00ean kh\u00f4ng \u0111\u01b0\u1ee3c forward data<\/li>\n<li>Listening (sau\u00a0Forward delay timer: 15s ): \u0111\u01b0\u1ee3c nh\u1eadn v\u00e0 g\u1eedi BPDU, kh\u00f4ng h\u1ecdc MAC, kh\u00f4ng forward data<\/li>\n<li>Learning (sau Forward delay timer: 15s): nh\u1eadn v\u00e0 g\u1eedi BPDU, h\u1ecdc MAC, kh\u00f4ng forward data<\/li>\n<li>Forwarding: nh\u1eadn+g\u1eedi BPDU, h\u1ecdc MAC, forward data<\/li>\n<\/ul>\n<p>Ta \u0111\u1ec3 \u00fd th\u1ea5y ph\u1ea3i m\u1ea5t 30s th\u00ec c\u00e1c c\u1ed5ng kh\u00f4ng b\u1ecb kh\u00f3a m\u1edbi \u0111\u01b0\u1ee3c ph\u00e9p forwarding, nh\u1eb1m m\u1ee5c \u0111\u00edch ch\u1ed1ng loop, v\u00ec c\u00f3 th\u1ec3 x\u1ea3y ra hi\u1ec7n t\u01b0\u1ee3ng kh\u00f4ng \u0111\u1ed3ng b\u1ed9 spanning tree tr\u00ean c\u00e1c switch, c\u00f3 th\u1ec3 kh\u00f4ng t\u00ednh to\u00e1n k\u1ecbp.<\/p>\n<hr \/>\n<p>C\u00f3 m\u1ed9t \u0111i\u1ec3m c\u00e1c b\u1ea1n ch\u00fa \u00fd, khi c\u1eafm m\u00e1y t\u00ednh v\u00e0o switch, c\u1ed5ng s\u1ebd m\u1ea5t 30s m\u1edbi c\u00f3 m\u1ea1ng, v\u1eady l\u00fd do t\u1ea1i sao? N\u00f3 c\u0169ng li\u00ean quan \u0111\u1ebfn spanning tree. M\u1eddi c\u00e1c b\u1ea1n \u0111\u1ecdc b\u00e0i ti\u1ebfp theo s\u1ebd r\u00f5 \ud83d\ude00<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Spanning Tree l\u00e0 giao th\u1ee9c ch\u1ed1ng loop tr\u00ean c\u00e1c thi\u1ebft b\u1ecb m\u1ea1ng (802.1d). N\u00f3 s\u1eed d\u1ee5ng BPDU packets \u0111\u1ec3 giao [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[29,30,32,33,25,16,26,27,28,21,6],"tags":[38,40,46,91,102,109,120],"class_list":["post-573","post","type-post","status-publish","format-standard","hentry","category-ccie-rs","category-ccna","category-ccnp-switch","category-ccnp-tshoot","category-cisco","category-courses","category-jncia","category-jncie","category-jncip","category-juniper","category-networking","tag-bid","tag-bpdu","tag-cach-hoat-dong-spanning-tree","tag-loop-free","tag-portfast","tag-spanning-tree","tag-tie-breaker"],"_links":{"self":[{"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=\/wp\/v2\/posts\/573","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=573"}],"version-history":[{"count":0,"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=\/wp\/v2\/posts\/573\/revisions"}],"wp:attachment":[{"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=573"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=573"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kb.lagonet.vn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=573"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}