一、级联简介
级联是交换机组网的一种结构，级联技术可以实现两台或两台以上交换机之间的互联，在多种网络中被广泛应用二、简单实验
实验拓扑：
1-1，1-2，1-3三台交换机级联至1-3；2-1，2-2两台级联至2-2；1-3和2-2上联至HX，所有网段网关都在HX上。
Server1A：10.3.1.1/24 10.3.1.254 vlan 10
Server1B：10.3.1.2/24 10.3.1.254 vlan10
Server2A：10.3.2.1/24 10.3.2.254 vlan 20
Server2B：10.3.2.2/24 10.3.2.254 vlan 20
Server3A：10.3.3.1/24 10.3.3.254 vlan 30
Server3B：10.3.3.2/24 10.3.3.254 vlan 30
开始配置：
交换机1-1配置：1口级联1-2，2口vlan30
vlan batch 10 20 30
#
interface GigabitEthernet0/0/1
port link-type trunk
port trunk allow-pass vlan 2 to 4094
#
interface GigabitEthernet0/0/2
port link-type access
port default vlan 30
交换机1-2配置：4口级联1-1，2口级联1-3，1口vlan10，3口vlan20
vlan batch 10 20 30
#
interface GigabitEthernet0/0/1
port link-type access
port default vlan 10
#
interface GigabitEthernet0/0/2
port link-type trunk
port trunk allow-pass vlan 2 to 4094
#
interface GigabitEthernet0/0/3
port link-type access
port default vlan 20
#
interface GigabitEthernet0/0/4
port link-type trunk
port trunk allow-pass vlan 2 to 4094
交换机1-3配置：2口级联1-2，3口上联HX，1口vlan20
vlan batch 10 20 30
#
interface GigabitEthernet0/0/1
port link-type access
port default vlan 20
#
interface GigabitEthernet0/0/2
port link-type trunk
port trunk allow-pass vlan 2 to 4094
#
interface GigabitEthernet0/0/3
port link-type trunk
port trunk allow-pass vlan 2 to 4094
交换机2-2配置：1口上联HX，2口级联2-1
vlan batch 10 20 30
#
interface GigabitEthernet0/0/1
port link-type trunk
port trunk allow-pass vlan 2 to 4094
#
interface GigabitEthernet0/0/2
port link-type trunk
port trunk allow-pass vlan 2 to 4094
交换机2-1配置：1口级联2-2，2口vlan10
vlan batch 10 20 30
#
interface GigabitEthernet0/0/1
port link-type trunk
port trunk allow-pass vlan 2 to 4094
#
interface GigabitEthernet0/0/2
port link-type access
port default vlan 10
HX配置：2口Trunk至1-3，3口Trunk至2-2，3类server的网关配置，1口vlan30
vlan batch 10 20 30
#
interface Vlanif1
#
interface Vlanif10
ip address 10.3.1.254 255.255.255.0
#
interface Vlanif20
ip address 10.3.2.254 255.255.255.0
#
interface Vlanif30
ip address 10.3.3.254 255.255.255.0
#
interface MEth0/0/1
#
interface GigabitEthernet0/0/1
port link-type access
port default vlan 30
#
interface GigabitEthernet0/0/2
port link-type trunk
port trunk allow-pass vlan 2 to 4094三、小结
1、trunk链路允许所有vlan通过，但级联的交换机需起相应vlan
2、vlan间通信依靠HX（三层交换）的直连路由