15
Loopback Testing
The following functions are available during loopback testing. During loopback
testing, management traffic entering the uplink port is still capable of managing the
device. This is selectable form the UNIT screen in a serial/Telnet session. There are
no LoopBack test options in iView²
The menu of choices in the CLI includes:
•
No loopback, normal traffic mode
•
Loopback Enabled
•
Loopback, Source/Destination address swap
•
Loopback, address swap and clear Multicast bit
•
No learning on fiber or Data ports
The menu of choices in iView² includes:
•
Off
•
ON
•
On-Address Swap
•
On-Address Swap + Clear MC
Loopback Testing on Remote or Standalone
No loopback, normal traffic mode
The standard mode in which the units function, either as stand-alone or
Host/Remote.
Loopback Enabled
Loopback mode without address swap
Source/Destination Address Swap
A Layer 2 Ethernet switch will discard all received packets with the same MAC
address as sent packets. To avoid this issue the Loopback feature can swap the source
and destination MAC addresses on the looped data. (This selection can cause a frame
with a multicast source address to be created, which violates the IEEE standard.)
Address Swap and Clear Multicast Bit
In addition to swapping the source and destination MAC addresses on the looped
data, the Loopback feature can also be set to clear the multicast bit. This allows the
looped data to avoid being blocked by any multicast settings.
Loopback Testing in a Host/Remote Configuration
Configure the Host by selecting No Learning on OPTICS and DATA Ports; on the
Remote, choose SRC/DST Address Swap or Address Swap and Clear Multicast Bit.
