VLAN help

Hi there,

I'm studying for my CCNA and am messing around with a few different VLAN scenarios.

Up until now, we have been taught to use different subnets for each vlan.

e.g. VLAN2 > 192.168.2.x VLAN3 > 192.168.3.x

However, I would like to see what happens when you have different VLAN's on the same subnet.

So, I've got two hosts;

Host A is on VLAN 2 and has an IP address 192.168.4.3/24 Host B is on VLAN 3 and has an IP address 192.168.4.20/24

I've configured the ports on the 2950 to enable static VLAN's for the two ports. Up until now, there is no problem...Host A can ping other hosts that have been assigned onto VLAN 2 and Host B can ping other hosts on VLAN 3. Neither can ping each other.

But, I'd like to configure inter-VLAN routing. Is this not possible because they are on the same subnet?

I've connected and configured a trunk link between the 2950 switch and a 2600 router, and set;

2600(config)# interface f0/1 2600(config-if)# no ip address 2600(config)# no shut 2600(config)# interface f0/1.2 2600(config-subif)# encapsulation dot1q 2 2600(config-subif)# ip address 192.168.4.1 255.255.255.0 2600(config-subif)# exit 2600(config)# interface f0/1.3 2600(config-subif)# encap dot1q 3 2600(config-subif)# ip address 192.168.4.19 255.255.255.0

However, Host A can ping both 192.168.4.1 and .4.10, whereas Host B can ping neither addresses.

Is it not possible to enable inter-vlan routing this way, or am I doing something wrong? I assume the problem is because you are assigning two subinterfaces on the same subnet on the router, but I thought that with the dot1q x command you were speciyfing that only VLAN x could communicate with it?

Would appreciate an explanation!

Thanks, Dilan