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  1. Switch

  2. Layer 2 Device Switchคือ อุปกรณ์ที่ใช้เป็นจุดศูนย์กลางในการ กระจายสัญญาณ หรือข้อมูล หลักการทำงาน Switch จะทำหน้าที่เลือกส่งข้อมูลถึงผู้รับ เท่าที่จำเป็นเท่านั้น Broadcasts are forwarded to allsegments Each segment has its own collision domain

  3. ARP ARP (Address Resolution Protocol) ใช้ในการสอบถามตาราง MAC Address จากอุปกรณ์ที่เราต้องการ ติดต่อเพื่อทราบตำแหน่งที่ใช้ในการติดตต่อ MAC Address มีลักษณะเป็นเลขฐาน 16 ยาว 6 ไบต์ เช่น 23:43:AA:5B:32:2C กลไกการทำงานของ ARP • ARP Request Packet ARP[IP, MAC Source. : IP MAC (FF.FF.) Des.]  • ARP Reply  Packet ARP[IP, MAC Source. : IP MAC (FF.FF.) Des.] Source ผู้ส่ง, Destination = (ผู้รับ)

  4. Transmitting Frames Cut-Through • Switch checks destination address and immediately begins forwarding frame. Store and Forward • Complete frame is received and checked before forwarding. Fragment-Free • Switch checks the first 64 bytes, then immediately begins forwarding frame.

  5. MAC Address Table • Initial MAC address table is empty.

  6. Learning Addresses • Station A sends a frame to station C. • 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).

  7. Learning Addresses (Cont.) • Station D sends a frame to station C. • 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).

  8. Filtering Frames • Station A sends a frame to station C. • Destination is known; frame is not flooded.

  9. Filtering Frames (Cont.) • Station A sends a frame to station B. • The switch has the address for station B in the MAC address table.

  10. Broadcast and Multicast Frames • Station D sends a broadcast or multicast frame. • Broadcast and multicast frames are flooded to all ports other than the originating port.

  11. Broadcast Storms • Host X sends a broadcast. • Switches continue to propagate broadcast traffic over and over.

  12. Spanning-Tree Protocol • Provides a loop-free redundant network topology by placing certain ports in the blocking state.

  13. Spanning-Tree Operation • One root bridge per network • One root port per nonroot bridge • One designated port per segment • Nondesignated ports are unused

  14. พิจารณา 1.BW 2 Path cost 3. MAC Spanning-Tree Protocol Root Bridge Selection • Bpdu = Bridge Protocol Data Unit (default = sent every two seconds) • Root bridge = Bridge with the lowest bridge ID • Bridge ID =

  15. Spanning-Tree Port States • Spanning-tree transits each port through several different states:

  16. Configuration Switch ลบconfigure # erase start up # reload ตรวจสอบconfigure #show running-config #show spanning-tree #show vlan #show interfaces status #show mac-address-table #show ip int brief

  17. Configuration Switch 2950 Vlan 1 default จะใช้ Vlan ได้ ตั้งแต่ vlan 2 – 4096 การ configure VLAN NAME Switch#show vlan Switch#vlan database Switch(vlan)#vlan 2 name aaa Switch(vlan)#vlan 3 name bbb Switch#configure terminal Switch(config)#interface FastEthernet 0/1-24 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 2

  18. Configuration Switch 2950 Vlan 1 default การ configure VLAN and port Access Switch#configure terminal Switch(config)#vlan 2 Switch(config-vlan)#name Sales Switch (config-vlan)#vlan 3 Switch (config-vlan)#name Marketing Switch(config)#interface FastEthernet 0/1-24 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 2

  19. Configuration Switch 2950 Configure trunk Switch#configure terminal Switch(config)#interface fastethernet 0/3 Switch(config-if)#switchport mode trunk Switch(config-if)#switchport trunk encapsulation dot1q ,isl VLAN Trunking Protocol (VTP) Switch#vlan database Switch(vlan)#vtp server, client , transparent Switch(vlan)#vtp domain jodoi Switch(vlan)#vtp password password Switch#show vtp status Cisco only

  20. VTP Modes • Creates VLANs • Modifies VLANs • Deletes VLANs • Sends/forwards advertisements • Synchronizes • Saved in NVRAM • Creates VLANs • Modifies VLANs • Deletes VLANs • Forwards advertisements • Does not synchronize • Saved in NVRAM • Forwards advertisements • Synchronizes • Not saved in NVRAM

  21. Spanning-Tree Path Cost