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I would like to create a network like the one in the screenshot. I would have 2 VLANs :
-VLAN10 : Service1
-VLAN20 : Service2

Routing is working but i don't know if I can have adresses on 192.168.1.X behind both routers. Because on both routers my FA0/0 needs to be reachable by each machine.

For exemple on the left, 192.168.1.2 and 192.168.2.3 need to be able to reach the gateway, but they are not on the same subnet, so how is it possible ? And even if this is possible, if I want 192.168.1.2 to ping 192.168.1.3, 192.168.1.2 will send ARP requests since it is the same subnet, and he won't try to reach the gatway. Dots are red because i did the screenshot while packet tracer was starting but routing is done.

Thank you in advance for your help :)

enter image description here

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 17 '17 at 3:45
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As you've drawn this, you can't do it. You can't have the same subnet in two locations (separated by a layer 3 link).

To make this work, you need 4 VLANS, two at each site. You can make the ones on the left 192.168.1.0/25 and 192.168.2.0/25, and the ones on the right 192.168.1.128/25 and 192.168.2.128/25.

The lower two routers will have a subinterface on each VLAN/subnet. The switch will trunk both VLANs to the router. You can apply any security filtering to the /24 block as needed.

If this were a real network, ask yourself why would you need to have the same subnet in both locations? There are rarely any strong reasons for doing so.

| improve this answer | |
  • well you could with VxLAN but I guess this is not the purpose here ;) – JFL Mar 3 '17 at 17:07
  • Thank you very much for your answer. Effectively it answers to my question. Now i'd like to know how would the DHCP be able to deliver the right IP addresses depending on the VLAN 'asking' him ? And imagine I have a service of 50 people working on different buildings in a company site. I thought it was possible to make them all on the same subnet, even across routers. – saperlipopette Mar 3 '17 at 22:11

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