業(yè)務支撐網(wǎng)網(wǎng)絡技術(shù)第二層交換機的功能(已修改)
2025-01-23 13:12 本頁面
【正文】 Lesson 7 第二層交換機的功能 第二層交換機的工作原理 生成樹協(xié)議 (STP) 高級生成樹協(xié)議 第二層交換機的基本配置 交換機的端口安全 第二層交換機的工作原理 ? 面板指示燈 ? 交換機和網(wǎng)橋的比較 ? 交換機的數(shù)據(jù)轉(zhuǎn)發(fā)方式 ? 第二層交換機的功能 ? 冗余 (Redundant) 面板指示燈 交換機和網(wǎng)橋的比較 網(wǎng)橋 (Bridge) 交換機(Switch) CutThrough（ 直通轉(zhuǎn)發(fā)） ? Switch checks destination address and immediately begins forwarding frame FragmentFree（ 碎片丟棄） ? Switch checks the first 64 bytes, then immediately begins forwarding frame Store and Forward（ 存儲轉(zhuǎn)發(fā)） ? Complete frame is received and checked before forwarding 交換機的數(shù)據(jù)轉(zhuǎn)發(fā)方式 第二層交換機的功能 ? 地址學習 (Address learning) ? 轉(zhuǎn)發(fā) /過濾決定 (Forward/filter decision) ? 避免循環(huán) (Loop avoidance) MAC地址表 (MAC Address Table) 交換機上電初始化期間 MAC地址表是空的 地址學習 (Learning Addresses) ? Station A sends a frame to station C. ? The switch caches the MAC address of station A to port E0 by learning the source address of data frames. ? The frame from station A to station C is flooded out to all ports except port E0 (unknown unicasts are flooded). 地址學習 (Learning Addresses) ? Station D sends a frame to station C. ? The switch caches the MAC address of station D to port E3 by learning the source address of data frames. ? The frame from station D to station C is flooded out to all ports except port E3 (unknown unicasts are flooded). 過濾幀 (Filtering Frames) ? Station A sends a frame to station C. ? The destination is known。 the frame is not flooded. 過濾幀 (Filtering Frames ) ? Station A sends a frame to station B. ? The switch has the address for station B in the MAC address table. ? Station D sends a broadcast or multicast frame. ? Broadcast and multicast frames are flooded to all ports other than the originating port. ? 廣播 MAC地址： 組播 MAC地址范圍 ： 01:00:5E:00:00:0001:00:5E:FF:FF:FF 廣播和組播幀 (Broadcast and Multicast Frames) 冗余 (Redundant) ? 優(yōu)點：冗余能夠避免單點故障 ? 缺點：交換循環(huán) (Switch loop) 交換循環(huán)的危害 ? 廣播風暴 (Broadcast Storms) ? 多幀復制 (Multiple Frame copies) ? MAC地址表不穩(wěn)定（ MAC Database Instability） ? Host X sends a broadcast. ? Switches continue to propagate broadcast traffic over and over. 廣播風暴 (Broadcast Storms) ? Host X sends a unicast frame to router Y. ? The MAC address of router Y has not been learned by either switch. ? Router Y will rec
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