Is it possible to assign a switch port to a VLAN based on the fact that the host IP address is on a certain subnet? I have found the following references from HP and Netgear, but I have been unable to find any such functionality for Cisco. Please note that this is only academic at this time.
In an IP subnet–based VLAN, all the end workstations in an IP subnet are assigned to the same VLAN. In this VLAN, users can move their workstations without reconfiguring their network addresses. IP subnet VLANs are based on Layer 3 information from packet headers. The switch makes use of the network-layer address (for example, the subnet address for TCP/IP networks) in determining VLAN membership. If a packet is untagged or priority tagged, the switch associates the packet with any matching IP subnet classification.
In this method, packets are assigned to VLANs based on their source IP addresses and subnet masks. A port configured with IP Subnet-based VLANs assigns a received untagged packet to a VLAN based on the source address of the packet. Use this feature when packets from an IP Subnet or IP address must be transmitted in a VLAN. This feature is available only on hybrid ports, and it processes only untagged packets.