Cisco – Required VLAN overlapping allowed

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.

Your problem is that, on the HQ1 router, you are attempting to put the same network on multiple routed interfaces. I think you mean these serial interfaces to be for point-to-point links. You should use a network (/31 or, if you are more traditional, /30) for your point-to-point links. You would then have two usable addresses for the links, and one of the two addresses goes on one end of the link, and the other address goes on the other end of the link.

Alternatively, you could use any other network size, but you need to use separate networks on the two interfaces in the same router.

Routers route between networks; they don't route from one network to the same network. How will the routing table know to which of the two interfaces in the same network it should forward packets for that network?