User manual

50 Publication 1783-UM003D-EN-E - December 2009
Chapter 2
Layer 3 Routing (Stratix
8300 Switch Only)
The Stratix 83000 Ethernet Managed Switch uses IP address routing to map
subnetworks (subnets) to an individual VLAN. In some network
environments, VLANs are associated with individual networks or
subnetworks. In an IP network, each subnetwork is mapped to an individual
VLAN. Configuring VLANs helps control the size of the broadcast domain
and keeps local traffic local. However, network devices in different VLANs
cannot communicate with one another without a Layer 3 device to route traffic
between the VLAN, referred to as inter-VLAN routing. You configure one or
more Layer 3 switches to route traffic to the appropriate destination VLAN.
The following figure shows a basic routing topology.
Switch A is in VLAN 10, and Switch B is in VLAN 20. The Layer 3 switch has
an interface in each VLAN.
When Host A in VLAN 10 needs to communicate with Host B in VLAN 10, it
sends a packet addressed to that host. Switch A forwards the packet directly to
Host B, without sending it to the Layer 3 switch.
When Host A sends a packet to Host C in VLAN 20, Switch A forwards the
packet to the Layer 3 switch, which receives the traffic on the VLAN 10
interface. The Layer 3 switch checks the routing table, finds the correct
outgoing interface, and forwards the packet on the VLAN 20 interface to
Switch B. Switch B receives the packet and forwards it to Host C.
Layer 3 Switch