R3204P16-HP Load Balancing Module Network Management Configuration Guide-6PW101

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Layer 2 forwarding configuration
NOTE:
The LB module supports Layer 2 forwarding configuration only in the command line interfaces (CLIs).
Layer 2 forwarding overview
Layer 2 forwarding involves general, inline, and inter-VLAN Layer 2 forwarding.
General Layer 2 forwarding
If the destination MAC address of an incoming packet matches the MAC address of the receiving Layer
3 interface, the device forwards the packet through that interface. If not, the device performs general
Layer 2 forwarding through a Layer 2 interface. The device looks up the MAC address table according
to the destination MAC address of the incoming packet, obtains the outgoing interface, and then
forwards the packet through the interface.
Inline Layer 2 forwarding
Inline Layer 2 forwarding comprises three types: forward, reflect, and blackhole.
• The forward type allows a device to forward packets received on an interface through another
interface, rather than through looking up the MAC address table.
• The reflect type allows a device to forward a packet through the interface that received the packet.
• The blackhole type allows a device to discard packets received on an interface.
The inline Layer 2 forwarding feature is supported on the interfaces and subinterfaces of the LB modules.
Inter-VLAN Layer 2 forwarding
Inter-VLAN Layer 2 forwarding accomplishes communications between VLANs at the data link layer.
As shown in Figure 15, a LB modu
le works with a switch to filter Layer 2 traffic arriving at the switch before
performing inter-VLAN Layer 2 forwarding.
Figure 15 Inter-VLAN Layer 2 forwarding
Inter-VLAN Layer 2 forwarding operates as follows:
After receiving a packet, the switch adds the VLAN tag of the receiving interface to the packet and if the
packet is not destined to the VLAN the switch tagged, sends the packet to the LB module through the trunk
port in between.
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