Austin's SWE Notes 😭

    Router On A Switch Setup

    Setup topo

    Pasted image 20250126165329.png

    Port Ethernet0 is in access  mode, with VLAN ID 1,
connected to VLAN1-PC-1 on port ens4
Port Ethernet1 is in access  mode, with VLAN ID 1,
connected to VLAN1-PC-2 on port ens4
Port Ethernet2 is in access  mode, with VLAN ID 2,
connected to VLAN2-PC-1 on port ens4
Port Ethernet3 is in access  mode, with VLAN ID 2,
connected to VLAN2-PC-2 on port ens4
Port Ethernet4 is in access  mode, with VLAN ID 3,
connected to VLAN3-PC-1 on port ens4
Port Ethernet5 is in access  mode, with VLAN ID 3,
connected to VLAN3-PC-2 on port ens4
Port Ethernet6 is in access  mode, with VLAN ID 4,
connected to VLAN4-PC-1 on port ens4
Port Ethernet7 is in dot1q  mode, with native VLAN 1,
connected to R1 on port FastEthernet0/0

    For each guest, we setup the IP following this format:

    VLAN1-PC-1: 192.168.1.2
VLAN1-PC-2: 192.168.1.3
...
VLAN3-PC-1: 192.168.3.2
VLAN3-PC-2: 192.168.3.3
...

    Each VLAN will have a default router for that. For example, VLAN1 will be default routed to 192.168.1.1 and VLAN3 will be default routed to 192.168.3.1.

    Setup the router

    We can do a show ip int brief to show the current configuration default.

    Since we only connect FastEthernet0/0. We are gonna enable this port:

    > en
> config terminal 
> int FastEthernet0/0
> no shutdown

    After this this port should be enable

    Next, we need to create Sub Interface:

    > en
> config terminal

# Create for vlan id 1
> int FastEthernet0/0.1 # .1 because vlan id 1
> encap dot1q 1 # same as vlan id
> ip address 192.168.1.1 255.255.255.0
> no shutdown 

...

# create for vlan id 3
> int FastEthernet0/0.3 
> encap dot1q 3
> ip address 192.168.1.3 255.255.255.0
> no shutdown 

...

    As a result, now we can ping cross vlan from 192.168.1.2 -> 192.168.3.2.

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