router virtual subinterface

We know that the port of the router connected to the terminal should be set as the gateway of the terminal, and now the switch divides a network segment into three through VLAN technology, so how to configure three gateway addresses for one port of the router? Sub-interface technology is needed now, virtualize a port into multiple interfaces, encapsulate their respective VLAN numbers, and configure gateway addresses for terminal devices in each VLAN. F0/0 can be divided into
f0/0.1, f0/0.2...
or Divide f0/1 into f0/1.1, f0/1.2...
and so
on

configuration steps

In global configuration mode
1. Create/enter sub-interface: interface sub-interface port number (such as int f0/0.1)
2. Encapsulation vlan number: encapsulation dot1Q vlan number (en do vlan number)
3. Set ip address: ip address IP address subnet mask (ip add IP address subnet mask)

About encapsulation: encapsulate which vlan number you want to be the gateway of any vlan
For example, if you want to create a f0/0.1 sub-interface as the gateway of the device in vlan10
int f0/0.1
en do 10
ip add 192.168.1.254 255.255.255.0
configuration is complete

configuration process

For example, configure three VLANs (10, 20, 30) on the switch
and configure three sub-interfaces on the router to assign gateways:

switch configuration

Put the mouse cursor on the switch and check the port information of the switch. 0/1, 0/2, and 0/3 are now enabled, but all VLANs are 1 by default. Now start to configure the switch
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Now let’s check the port information of the switch again. The
created vlan has been assigned to the port, and the vlan of port 0/4 is –, which proves that it is now in trunk mode.
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router interface configuration

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Up to now, the three sub-interfaces of the router have been configured as the gateway of the corresponding vlan network segment