How to Configure Subinterfaces on a Cisco Router

The reason that this doesn't work is that your desktop isn't actually in vlan 200. You changed the IP address of the desktop to be on the 192.168.200.0/24 subnet but that's at layer 3.

Looking at the layer 2 topology, your PC is connected to a dumb switch which is hooked into a vlan 1 port on the managed switch. Because of this, regardless of what your IP address is the traffic coming from your desktop is hitting the switch on vlan 1.

Going back to layer 3 a bit, your default gateway 192.168.200.254 isn't in vlan 1 it's in vlan 200 because it's assigned to a router sub-interface which is watching for traffic tagged vlan 200. Therefore the PC's default gateway is unreachable at layer 2 and you get the infamous "Destination host unreachable" error.

For you to add a host in vlan 200, you need to plug it into a totally new port on the Dell managed switch and assign that port to vlan 200, as well as giving it an IP address in the 192.168.200.0/24 subnet.

On a related note, if you want traffic from vlan 200 to reach the outside internet you will need to create static routes on both the virgin media router and the Cisco router telling them about the other networks.

On the Cisco router you need to add ip route 0.0.0.0 0.0.0.0 192.168.1.1 to tell it to forward any traffic with a destination network it doesn't know about to virgin media. On the virgin media router you need the equivalent of ip route 192.168.200.0 255.255.255.0 192.168.1.254 so that the virgin media router knows where to send traffic coming back from the internet destined for vlan 200.

first of all your topology seams to be as following

following your description

pc2 could reach PC1 cause the pc2 GW (which is R2) can reach PC1 (cause it is directly connected to the both network).

so same way let us ask a very importent question . what is the PC1 GW and do PC1 GW know about subnet 192.168.2.X or not ?????????

if PC1 GW is the modem so you must add static route on the modem tell it if you want to reach 192.168.2.X you should go to 192.168.1.2 . otherwise you need to set the GW of PC1 to be 192.168.1.2