5.1.1 Emulation Bypass
By default, all frames bridged by the Linktropy appliance are assumed to be part of the WAN
traffic and are subjected to the configured WAN link conditions. This includes ARP and multicast
traffic, which on a production network may be processed or filtered prior to traversal of the WAN
link.
The Emulation Bypass
row is used to specify whether ARP and multicast frames are to be included
as part of the emulated WAN traffic or be passed directly between the LAN A and LAN B
interfaces. ARP and multicast frames will bypass the emulated link and be passed directly between
the two interfaces when the corresponding boxes are checked. Frames that bypass the WAN
emulation are not subjected to loss or delay and do not consume emulated link bandwidth.
5.1.2 Learning Bridge
By default, the Learning Bridge feature is disabled and the Linktropy WAN emulator forwards all
frames received on the LAN A and LAN B interfaces to the opposite side. This provides the fastest
packet handling rates and highest throughput, and is recommended except when learning bridge
functionality is specifically required.
When the box labeled “Enable MAC address learning/filtering” is checked, the Linktropy WAN
emulator acts as a learning bridge and provides MAC address learning and filtering. The device
examines the source MAC address of received frames to learn the network segment (LAN A or
LAN B) on which each directly connected device is located. Received frames for which the source
and destination devices are on the same network segment are discarded.
Learning Bridge functionality is generally only required when connecting multiple devices on a
network segment through a repeater/hub. When using a switch, the switch provides the filtering
functionality and learning bridge functionality is not needed on the Linktropy WAN emulator.
5.2 IP Routing Mode
In IP Routing Mode, the Linktropy WAN emulator functions as a router between the Ethernet
segments connected to the LAN A and LAN B ports.
IP Routing Mode provides a default routing mechanism that eliminates the need for multiple
static routes. When a gateway address is set for both interfaces, the default next-hop for packets
received on one interface is the gateway address of the opposite interface. For example, if a
packet is received on the LAN A interface and has a destination address on a subnet that is not
directly connected to either the LAN A or LAN B interface, the packet is forwarded across the
emulated link to the LAN B gateway router.
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