Figure 6–2 shows the data flow in the bypass modes. Note that the internal system COM1
port is connected directly to the external COM1 port.
NOTE:
You can connect a serial terminal to the external COM1 port in any of the bypass
modes.
Snoop Mode
In Snoop mode data partially bypasses the RMC. The data and control signals are routed
directly between the system COM1 port and the external COM1 port, but the RMC taps into
the data lines and listens passively for the RMC escape sequence. If it detects the escape
sequence, it enters the RMC CLI.
The escape sequence is also passed to the system on the bypassed data lines. If you decide
to change the default escape sequence, be sure to choose a unique sequence so that 1) the
system software does not interpret characters intended for the RMC and 2) you ensure that
you don’t inadvertently invoke the RMC CLI.
In Snoop mode the RMC is responsible for configuring the modem for dial-in as well as
dial-out alerts and for monitoring the modem connectivity.
Because data passes directly between system COM1 port and the 9-pin external COM1 port
(bypassing the DUART), Snoop mode is useful when you want to monitor the system but
also ensure optimum COM1 performance.
In Snoop mode, the RMC also broadcasts power-up and power-down error messages
through the COM1 port. Additional RMC broadcast messages may occur when the RMC
CLI is active.
Soft Bypass Mode
In Soft Bypass mode all data and control signals are routed directly between the system
COM1 port and the external COM1 port, and the RMC does not listen to the traffic on the
COM1 data lines. The RMC is responsible for configuring the modem and monitoring the
modem connectivity. If the RMC detects loss of carrier or the system loses power, it
switches automatically into Snoop mode. If you have set up the dial-out alert feature, the
RMC pages the operator if an alert is detected and the modem line is not in use.
Soft Bypass mode is useful if management applications need the COM1 channel to perform
a binary download, because it ensures that RMC does not accidentally interpret some binary
data as the escape sequence.
Using the Remote Management Console
6-7
