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254 Rockwell Automation Publication 1783-UM007I-EN-P - December 2017
Chapter 3 Configure Switch Features
Routing, Layer 3 Layer 3 routing is available on the following switches:
•
Stratix 5400 with Layer 3 firmware
•
Stratix 5410 with Layer 3 firmware
•
Stratix 8300 base units
Layer 3 routing uses IP address information to map subnetworks to an
individual VLAN. In some network environments, VLANs are associated with
individual networks or subnets. In an IP network, each subnetis 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 capable switches to route traffic to the
appropriate destination VLAN.
Figure 43 shows a basic routing topology.
Figure 43 - Example of 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 communicates with Host B in VLAN 10, it sends a
packet that is 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.
STCN Interface Optionally, configure the port to send Segment Topology Change Notices (STCNs) when the topology changes. If you configure this option,
also specify the segment ID that receives the STCNs from this port. The default is None.
TCNs are used within the segment to notify REP neighbors of topology changes. At the edge of the segment, REP can propagate the
notification to the STP or to the other REP segments.
STCN Segment Configure STCNs to a segment ID. The valid range is 1…1024. You can also configure a sequence of segments.
STCN STP Check STCN STP to send STCNs to STP networks. Be sure that the connection is at the segment edge. An STP connection that is not at the
edge could cause a bridging loop because STP does not run on REP segments. All STP BPDUs are dropped at REP interfaces.
By default, the checkbox is cleared.
Table 96 - REP Fields (Continued)
Field Description
Layer 3 Switch
VLAN 10 VLAN 20
Host
Host
ISL Trunks
Switch A
Switch B
Host