I am studying for ICND1 through CBTNuggets,

I recently watched videos on how to interact between different vlans using separate interfaces, sub-interfaces and Layer 3 Switching.

The first two worked fine for me, but the Layer 3 Switching is not working when i am pinging PC in one VLAN to the PC in other VLAN.

Suppose PC A is connected to Fa0/1 of Switcher and PC B is connected to Fa0/2 of Switcher.

Here is what I did,

I went to Switcher CLI, Went to Global Configuration mode,

created two vlans using commands,

# vlan 10
# vlan 20

Now I moved fa0/0 port to vlan 10 and fa0/1 port to vlan 20

I assigned IP addresses to PCs,

PC A (fa0/1): 

Default Gateway: Subnet Mask:

PC B (fa0/2):

Subnet Mask: Default Gateway:

Now i went to the CLi of switcher and did this in Global mode,

# interface vlan 10
# ip address
# no shutdown
# exit
# interface vlan 20
# ip address
# no shutdown
# exit

Both vlans 10 and 20 are up and running and all the ports are up too, but I couldn't be able to ping PC B from PC A.

This is exactly what the guy did in the video and he managed to ping.

What did i miss ?

P.S: I also tried to erase arp tables but still couldn't be able to ping.

  • Please post the switch config. Jul 7, 2014 at 11:42
  • 1
    I am guessing it is a typo, but generally there is no Fa0/0. Did you mean that you moved Fa0/1 to VLAN 10 and Fa0/2 to VLAN 20?
    – YLearn
    Dec 4, 2014 at 19:28

2 Answers 2


On the switch, your IP for interface vlan 20 is wrong.

# interface vlan 20
# ip address
# no shutdown

Then make sure you have ip routing on.

Also the gateway for PC A should be while the gateway for PC B should be The subnet mask should be not the gateway.

Once fixed, make sure you can ping the gateway of each PC from the respective PCs as well.


According to you, PC'B' is on fa0/2. This means that PC'B' is on VLAN 1 by default. And PC'A' is in VLAN 20.

That is the mistake i guess


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