Advanced Configuration and Management Guide
For example, if you configure two IP sub-net VLANs on a routing switch, you can configure a virtual interface on each VLAN, then configure IP routing parameters for the sub-nets. Thus, the routing switch forwards IP sub-net broadcasts within each VLAN at Layer 2 but routes Layer 3 traffic between the VLANs using the virtual interfaces.
NOTE: The routing switch uses the lowest MAC address on the device (the MAC address of port 1 or 1/1) as the MAC address for all ports within all virtual interfaces you configure on the device.
The routing parameters and the syntax for configuring them are the same as when you configure a physical interface for routing. The logical interface allows the routing switch to internally route traffic between the protocol based VLANs without using physical interfaces.
All the ports within a protocol-based VLAN must be in the same port-based VLAN. The protocol-based VLAN cannot have ports in multiple port-based VLANs, unless the ports in the port-based VLAN to which you add the protocol-based VLAN are 802.1p tagged.
You can configure multiple protocol-based VLANs within the same port-based VLAN. In addition, a port within a port-based VLAN can belong to multiple protocol-based VLANs of the same type or different types. For example, if you have a port-based VLAN that contains ports 1 – 10, you can configure port 5 as a member of an AppleTalk protocol VLAN, an IP protocol VLAN, and an IPX protocol VLAN, and so on.
IP Sub-Net, IPX Network, and AppleTalk Cable VLANs
The protocol-based VLANs described in the previous section provide separate protocol broadcast domains for specific protocols. For IP, IPX, and AppleTalk, you can provide more granular broadcast control by instead creating the following types of VLAN:
•IP sub-net VLAN – An IP sub-net broadcast domain for a specific IP sub-net.
•IPX network VLAN – An IPX network broadcast domain for a specific IPX network.
•AppleTalk cable VLAN – An AppleTalk broadcast domain for a specific cable range.
You can configure these types of VLANs on routing switches only. The routing switch sends broadcasts for the IP sub-net, IPX network, or AppleTalk cable range to all ports within the IP sub-net, IPX network, or AppleTalk cable VLAN at Layer 2.
The routing switch routes packets between VLANs at Layer 3. To configure an IP sub-net, IPX network, or AppleTalk cable VLAN to route, you must add a virtual interface to the VLAN, then configure the appropriate routing parameters on the virtual interface.
NOTE: The routing switch routes packets between VLANs of the same protocol. The routing switch cannot route from one protocol to another.
NOTE: IP sub-net VLANs are not the same thing as IP protocol VLANs. An IP protocol VLAN sends all IP broadcasts on the ports within the IP protocol VLAN. An IP sub-net VLAN sends only the IP sub-net broadcasts for the sub-net of the VLAN. You cannot configure an IP protocol VLAN and an IP sub-net VLAN within the same port-based VLAN.
This note also applies to IPX protocol VLANs and IPX network VLANs, and to AppleTalk protocol VLANs and AppleTalk cable VLANs.
1.The acronym “VE” stands for “Virtual Ethernet”.
