metrotek Bercut-ETL, Operating Manual

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4. Loopback
Bercut-ETL is intended for loopback performing. Incoming traffic is be-
ing retransmitted backward with possibility of source and destination MAC/IP
addresses and TCP/UDP port numbers swapping.
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 (including error frames)
is being retransmitted backward without changing.
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2
4 5
1
2
4 5
Figure 4.1. Loopback at the physical layer
All the connection schemes use the following notation:
– MAC Src — source MAC address;
– MAC Dst — MAC address of Bercut-ETL ;
– 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.
Bercut-ETL. Operating manual