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Configuring and Managing External Modems
Supporting Dial-In Modems
DC-150
Cisco IOS Dial Technologies Configuration Guide
Figure 24 EXEC Creation on a Line Configured for Modem Dial-In
Note The modem callin and modem cts-required line configuration commands are useful for SLIP
operation. These commands ensure that when the line is hung up or the CTS signal drops, the line
reverts from Serial Line Internet Protocol (SLIP) mode to normal interactive mode. These commands
do not work if you put the line in network mode permanently.
Although you can use the modem callin line configuration command with newer modems, the modem
dialin line configuration command described in this section is more appropriate. The modem dialin
command frees up CTS input for hardware flow control. Modern modems do not require the assertion
of DTR to answer a phone line (that is, to take the line off-hook).
high,
watching
Lower DTR
Ringing
Idle state
Ready and active
Ring transition
CTS raised
DTR
CTS
Create EXEC
Raise DTR
Lower DTR
close connection
DTR high
CTS lowered
or exit
Answer
timeout
DTR low
Hang up
S1001a
DTR low,
watching
CTS