Configuring IP IP Forwarding
OmniSwitch AOS Release 7 Network Configuration Guide June 2013 page 15-7
IP Forwarding
Network device traffic is bridged (switched) at the Layer 2 level between ports that are assigned to the
same VLAN. However, if a device needs to communicate with another device that belongs to a different
VLAN, then Layer 3 routing is necessary to transmit traffic between the VLANs. Bridging decides to
forward the packets based on the destination MAC address of the packet. Routing decides on where to
forward packets based on the IP network address of the packet (for example, IP - 21.0.0.10).
Alcatel-Lucent switches support routing of IP traffic. A VLAN is available for routing when at least one-
router interface is defined for that VLAN and at least one active port is associated with the VLAN. If a
VLAN does not have a router interface, the ports associated with that VLAN are in essence firewalled
from other VLANs.
IP multinetting is also supported. A network is said to be multinetted when multiple IP subnets are brought
together within a single broadcast domain. Each interface is configured with a different subnet. As a
result, traffic from each configured subnet can coexist on the same VLAN.
In the illustration below, an IP router interface has been configured on each VLAN. Therefore,
workstations connected to ports on VLAN 1 on Switch 1 can communicate with VLAN 2; and
workstations connected to ports on VLAN 3 on Switch 2 can communicate with VLAN 2. Also, ports
from both switches have been assigned to VLAN 2, and a physical connection has been made between the
switches. Therefore, workstations connected to VLAN 1 on Switch 1 can communicate with workstations
connected to VLAN 3 on Switch 2.
IP Forwarding
Switch 2
130.0.0.1 130.0.0.2
VLAN 3
Switch 1
VLAN 1
110.0.0.1 110.0.0.2
Physical
Connection
IP Router Interface
=
VLAN 2
120.0.0.0
VLAN 2
120.0.0.0
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