You can configure one of your ports with an IP address, and then create another VLAN. Make that switchport a member of the VLAN. If you don't have the option of creating VLANs, you won't be able to do it.
Router#vlan-switch
Router(vlan-switch)#vlan100
Router(vlan-switch)#exit
Router#
It may tell you that you already have the max amount of vlans that the switch supports.
HTH
--John
HTH,
John
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