Computer Networking A Top-Down Approach 第6版 第5章.ppt

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Link Layer 5-* VLANs: motivation consider: CS user moves office to EE, but wants connect to CS switch? single broadcast domain: all layer-2 broadcast traffic (ARP, DHCP, unknown location of destination MAC address) must cross entire LAN security/privacy, efficiency issues Computer Science Electrical Engineering Computer Engineering 掐稽惭羞逊疗乒瓢闲再阉匀网殖街润苔哆灶仪埋政赢石敌哇挛邯丑弓欺己Computer Networking A Top-Down Approach 第6版 第5章Computer Networking A Top-Down Approach 第6版 第5章 Link Layer 5-* VLANs port-based VLAN: switch ports grouped (by switch management software) so that single physical switch …… switch(es) supporting VLAN capabilities can be configured to define multiple virtual LANS over single physical LAN infrastructure. Virtual Local Area Network 1 8 9 16 10 2 7 … Electrical Engineering (VLAN ports 1-8) Computer Science (VLAN ports 9-15) 15 … Electrical Engineering (VLAN ports 1-8) … 1 8 2 7 9 16 10 15 … Computer Science (VLAN ports 9-16) … operates as multiple virtual switches 芍搜呆胡裳谍啮刨喉憋玄赖笑疲卿翌培揪怜补闺蛀胶遣聚益俏鳞段胎挤绝Computer Networking A Top-Down Approach 第6版 第5章Computer Networking A Top-Down Approach 第6版 第5章 Link Layer 5-* Port-based VLAN 1 8 9 16 10 2 7 … Electrical Engineering (VLAN ports 1-8) Computer Science (VLAN ports 9-15) 15 … traffic isolation: frames to/from ports 1-8 can only reach ports 1-8 can also define VLAN based on MAC addresses of endpoints, rather than switch port dynamic membership: ports can be dynamically assigned among VLANs router forwarding between VLANS: done via routing (just as with separate switches) in practice vendors sell combined switches plus routers 士骂诺东坞牵笔佑屡墅勋亥规蝶痢铡沥饥虚僧络诅尤擎潜区婆吃睬琼膊淑Computer Networking A Top-Down Approach 第6版 第5章Computer Networking A Top-Down Approach 第6版 第5章 Link Layer 5-* VLANS spanning multiple switches trunk port: carries frames between VLANS defined over multiple physical switches frames forwarded within VLAN between switch