Allied Telesis AT-S70 - Manual (Page 88)

Chapter 8: Operations, Administration, and Maintenance (OAM)
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One important aspect of the IEEE 802.3ah OAM spec is that an OAM
entity may be in either Active or Passive mode.
ˆ Active Mode – Active-mode stations forward OAM communications
and can send queries and commands to a remote station.
ˆ Passive Mode – Passive-mode stations wait for the peer station to
forward OAM communications and then respond to commands and
queries. Generally, passive-mode do not initiate communications.
By default, the Converteon line card should come up in Passive mode for
OAM discovery (as per the IEEE 802.3ah). In order to initiate OAM
discovery, the line card needs to be configured in the Active mode by the
AT-CV5M01 CPM card. Therefore, if a line card is in a chassis with no
CPM card, it will come up in Passive mode.
The difference between the modes is that an OAM active-mode station
has more control on its peer than an OAM passive-mode station. For
example, an active-mode station can put a passive-mode station into
loopback mode, but not vice versa.