metrotek ETS-1000L, Руководство по эксплуатации

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5. Loopback
The Loopback function is necessary for networks testing in compliance with
the RFC 2544, as well as for a number of other tasks. This function allows to test
the network without changing it’s settings.
Network testing with the Loopback function can be performed at the four OSI
layers, jumbo frames are supported (up to 9600 byte).
•
At the Physical layer (L1) all the incoming traffic is being retransmitted
backward without changing.
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5
1
2
4 5
Figure 5.1. Loopback at the physical layer
All the connection schemes use the following notation:
– MAC Src — source MAC address;
– MAC Dst — destination MAC address;
– IP Src — source IP address;
– IP Dst — destination IP address.
– TCP/UDP Dst — destination TCP/UDP port number;
– TCP/UDP Src — source TCP/UDP port number.
• At the Data link layer (L2) , the incoming traffic (without error frames) is
being retransmitted backward with swapping destination and source MAC
addresses.
ETS-1000L. Operating manual