I have use three switches, and three different networks. In one switch, there are four PCs connected with two VLANs. I do the same thing to the other two switches, and I use trunks to connect the switches. I sent packets to another network using same VLAN ID, but the packets failed to reach the destination.

How do I send the packets?

  • 2
    If you want us to help you, you must provide the device configurations and a simple diagram showing how they're connected. You haven't provided enough information to help you.
    – Ron Trunk
    Jun 7, 2017 at 18:09
  • 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 can provide and accept your own answer.
    – Ron Maupin
    Feb 19, 2018 at 4:50

1 Answer 1


When a host sends traffic destined for a different network, it sends it to it configured gateway (usually a router), which is the host on a LAN that knows how to forward the traffic toward the destination network.

A host will compare its network with the destination network by masking the source and destination addresses on the layer-3 packet to see if they are on the same network. If the source and destination addresses on the layer-3 packet are in the same network, the host will encapsulate the the layer-3 packet in a layer-2 frame with the address of the destination host. If the networks are different, when the host will encapsulate the layer-3 packet in a layer-2 frame with the layer-2 address of its configured gateway.

That means that traffic sent to a different layer-3 network will be sent directly to the gateway, not the destination host.

In order for you to send traffic from one network to a different network, you need a router that knows how to get to each network.

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