Brocade FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide - Manual (Page 365)

Virtual routing interfaces
A virtual routing interface is a logical routing interface that Brocade Layer 3 Switches use to route Layer
3 protocol traffic between protocol VLANs.
Brocade devices send Layer 3 traffic at Layer 2 within a protocol VLAN. However, Layer 3 traffic from
one protocol VLAN to another must be routed.
If you want the device to be able to send Layer 3 traffic from one protocol VLAN to another, you must
configure a virtual routing interface on each protocol VLAN, then configure routing parameters on the
virtual routing interfaces. For example, to enable a Layer 3 Switch to route IP traffic from one IP subnet
VLAN to another, you must configure a virtual routing interface on each IP subnet VLAN, then configure
the appropriate IP routing parameters on each of the virtual routing interfaces.
The following figure shows an example of Layer 3 protocol VLANs that use virtual routing interfaces for
routing.
Virtual routing interfaces
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