switch or other device？

i want to get a network device working as a multiplexer.
for example, the data sent to port A would be forwarded to port B
completely.
i can also forward the data of port C to port B, at the same time port
A did not work any more.
the forward channel described above can work separately.
i need four channel work concurrently.

the first tech i was considered is a switch with VLAN.
any other idea or model(1Gb ether needed)？
.

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