VLAN實(shí)驗(yàn)：三層交換原理

Switch#vlan database
    % Warning: It is recommended to configure VLAN from config mode,
      as VLAN database mode is being deprecated. Please consult user
      documentation for configuring VTP/VLAN in config mode.
    Switch(vlan)# vlan 2 name marking
    VLAN 2 added:
        Name: marking
    Switch(vlan)# vlan 3 name counting
    VLAN 3 added:
        Name: counting

2 分配端口
    Switch(config)#interface FastEthernet0/1
    Switch(config-if)#switchport mode access
    Switch(config-if)#switchport access vlan 2
    Switch(config-if)#exit
    Switch(config)#interface FastEthernet0/2
    Switch(config-if)#switchport access vlan 2
    Switch(config-if)#interface FastEthernet0/3
    Switch(config-if)#switchport access vlan 3
    Switch(config-if)#interface FastEthernet0/4
    Switch(config-if)#switchport access vlan 3
    Switch(config-if)#exit
    Switch(config)#exit
    Switch#

    3 Show vlan 查看信息

Switch#show vlan

VLAN Name                             Status    Ports
    ---- -------------------------------- --------- -------------------------------
    1    default                          active    Fa0/5, Fa0/6, Fa0/7, Fa0/8
                                                    Fa0/9, Fa0/10, Fa0/11, Fa0/12
                                                    Fa0/13, Fa0/14, Fa0/15, Fa0/16
                                                    Fa0/17, Fa0/18, Fa0/19, Fa0/20
                                                    Fa0/21, Fa0/22, Fa0/23, Fa0/24
    2    marking                          active    Fa0/1, Fa0/2
    3    counting                         active    Fa0/3, Fa0/4
    1002 fddi-default                     active
    1003 token-ring-default               active
    1004 fddinet-default                  active
    1005 trnet-default                    active

VLAN Type  SAID       MTU   Parent RingNo BridgeNo Stp  BrdgMode Trans1 Trans2
    ---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
    1    enet  100001     1500  -      -      -        -    -        0      0
    2    enet  100002     1500  -      -      -        -    -        0      0
    3    enet  100003     1500  -      -      -        -    -        0      0
    1002 enet  101002     1500  -      -      -        -    -        0      0
    1003 enet  101003     1500  -      -      -        -    -        0      0

其實(shí)做這個(gè)實(shí)驗(yàn)很簡單就是劃分子網(wǎng)，主要是為了說明三層交換機(jī)最本質(zhì)工作原理，即一次路由，多次交換  結(jié)合arp的工作原理，兩臺(tái)主機(jī)通訊時(shí)，傳統(tǒng)的2層交換機(jī)進(jìn)行arp廣播尋找目標(biāo)mac地址，，當(dāng)目的主機(jī)在同一網(wǎng)段內(nèi)時(shí)，不需涉及網(wǎng)關(guān)。否則由網(wǎng)關(guān)回復(fù)arp廣播。

傳統(tǒng)的2層交換模塊不能實(shí)現(xiàn)網(wǎng)間互訪，而三層交互交換機(jī)的三層路由模塊把源和目的IP地址緩存交換機(jī)中，隨后第3層中跨子網(wǎng)的包傳送將不再由路由器來進(jìn)行。實(shí)驗(yàn)中的三層交換機(jī)充當(dāng)了傳統(tǒng)網(wǎng)絡(luò)中的路由器的角色，通過它可以實(shí)現(xiàn)網(wǎng)間互訪。