again , it is possible
but makes little sense to do with openwrt if you have access to proper
managed layer 2 switch with the option to do so ( cisco catalysts, and private vlans etc..)
As with openwrt on majority of devices you will be limited with number of ports ,
and then you would need to daisy chain many devices trough other switches
to a single port on openwrt thus limiting the bandwidth to a single ports speed.
On proper switches you will not have that limitation . you could have
many devices talking to a single server with a bonded(cisco-etherchannel-loadballanced)
interface - or multiple servers at the same time each pushing max port speed.