EXFO ETS-1000 - Manual (Page 49)

Connecting Unit
Ethernet Tester Analyzer 41
Unit Connection Schemes
All the connection schemes use the following notation:

MAC s — source MAC address

MAC d — destination MAC address

MAC R — gateway MAC address

IP s — source IP address

IP d — destination IP address
The figure above shows analyzer connection to a network with
equipment operating on both the Data Link and Network layers (for
example, switches and routers). Unlike the first case, with this
connection scheme both source and destination MAC and IP
addresses are swapped and the traffic is returned to the source port.
In the case of testing networks/equipment with capability of IP-traffic
routing, two unit ports are used. Packets are rerouted from one port to
another via a router. In addition, ETS-1000 can be connected to a
network switch.