You can use VLAN tagging if your ethernet card supports it, then this can be easily accomplished. Otherwise, you may need to look at another solution (an additional NIC card for the other subnet) unless someone has a better idea.
Usually we are able to just use VLAN tags and the NIC card to separate the traffic for each subnet, then again, it is hardware dependent in some cases. You may want to ask your provider as all networks are designed differently.
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