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12.4 Loopback
The Loopback is a feature of NP2000 GigE-BAS option that allows looping Ethernet traffic back to the sender, on Layer 1,
Layer 2 and Layer 3 to run various round trip tests.
Loopback supports following modes:
• Layer 1 – equivalent of a hardwire cable loop. 100% of the Ethernet signal
is looped.
• Layer 2 – the incoming frames are re-transmitted after exchanging the
source and destination MAC address.
• Layer 3 – the incoming frames are re-transmitted after exchanging the
source and destination addresses at IP and MAC layer. If Layer 3 loopback
doesn’t find IP header in received frame, then swaps only MAC layer
addresses.
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