tailieunhanh - Chapter7 Layer 2 Switching

Three Switch Function at Layer 2 层 2 交换的一些功能: (address learning):通过查看帧的源MAC地址来加进1个叫做转发/过滤表的MAC 地址数据库里 (forward/filter decisions):当 1 个接口收到 1 个帧的时候,switch 在 MAC 地址 数据库里查看目标 MAC地址和出口接口,然后转发到符合条件的那个目标端口去 (loop avoidance):假如有冗余的连接,可能会造成循环的产生,STP 就用来破坏这些 循环 . | Chapter Layer 2 Switching Switching Services Kit i ffi g 3 W M switches IB Ml lW t Mtcl LL 2 MW L M MMSL MWK Spanning Tree Protocol STP M bridges MM M J in iS. MAC MLM switches ASICs JMiOWS MAC ML L L switches SM SQft bridges L 2 W switches bridges ft 3 W router H M M MWWI S L 3 LLig mtmwwfttt MmmtL 1 -wmww n MLM 1 AT-j-t L 2 llfWWO ASIC 2. wire speed 3. MMW latency 4m Bridging vs. LAN Switching WM 2 T- E T i 1. bridges M M switches M M 2. switches HW bridges 3. bridges L bridge LHW 1 L M W switches L WM i 4. switches W nL M bridges 5. rn w 2 r 6MWO ttfo MAC ML .imo 2 ml l Three Switch Function at Layer 2 L 2 fi- 1. ML address learning ffi W MAC ML inS 1 W MAC MMWB 2. forward filter decisions 1 tin llj 1 WW switch MAC ML WMB @M mac MLin nmM m MWW@M n 3. M loop avoidance WX WM LM M MWML STP iM fi MM W Spanning Tree Protocol STP Spanning Tree Terms Digital Equipment Coporation DEC Compaq WWf .ft JMT W STP IEEE WgBW STP Rp W STP. ZMW DEC W STP STP W tf M M 2 WfM .STP MM spanning-tree M S i STP W bridges ffl BPDU BI JW Mft ffi nW W 2. W root bridge WWft W bridge ID BP W W W n M biock Snft WMiWW 3. BPDU Bridge Protocol Data UnitJPiWW switches ffi M W switch 4. bridge ID STP SS IW W W ID bridge tt priority MAC tt mWm WBP W 4. WW nonroot bridge MWWW WW. WW BPDUs MM STP fe 5. W n root port W M ffi W n MWWftft W n. MWW W 1 omm mo fomwmm bridge WftM 6. n designated port MW H. H 7. n port cost i T A T 8. H roD nondesignated port M. M blocking mode BP 9. n forwarding port n tt 10. B n blocked port tt W M fiM ffi listen tt Spanning Tree Operations WS STP Mft M ara M W TO WMX 3mSTP w 1 mMWM M . WM switches URT B WW M- WW bridge S W n. i switches WW .H W 1 Dft n Selecting the Root Bridge bridge ID STP B WWW ID M 8 . W MAC M .IEEE WW STP WMU M 32768. Mm - tt MAC iW bW W Selecting the Designated Port W 1 g9ft t ttgSn a Ri W AWSn TWM- Agte --- - 2 4 19 100 Spanning-Tree Port .