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I have a doubt with subnets and their gateways. For example assume I have four subnets using a mask of





If the router only can has an address (let's say, which are the gateways of the subnets B,C and D and how are they going to have internet connection?

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Your gateway must have an address on the subnet or it won't be accessible by other devices on the subnet. So in your example given above only the devices in subnet A would be able to access the gateway. – heavyd Mar 15 '13 at 17:17
but then, each subnet must have a router? – yzT Mar 15 '13 at 18:24
up vote 1 down vote accepted

Subnets are logically isolated from each other so yes, if you want each subnet to have a router, then you have to put a router in each subnet. Of course, you can put one physical router into 4 logical subnets by assigning it multiple addresses, one per subnet. If you can't assign multiple addresses to your router, then you're out of luck for 3 of the subnets.

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I'm just checking Google pictures and I'm seeing that each subnet has a router. I don't know why I had in mind that only a router were needed. – yzT Mar 15 '13 at 18:49

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