3Com MSR 50 Series Configuration Manual page 811

The terminal has baud rates different from those of the asynchronous interface.
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The corresponding device is not configured in file inittab.
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The router and the Unix server use different application modes, for example,
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the Unix server may use the many-to-one mode and the router may use the
one-to-one mode. Note that the router only supports the one-to-one mode
currently.
Solution:
For the first case, you may check the UNIX server log for a message similar to
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"open ptyp10 failed: I/O error. In such a case, execute the following command
on the Unix server:
# ps -ef | grep ttyp10
Then, kill all the displayed processes associated with ttyp10.
For the second case, you must reconfigure the baud rates to be consistent.
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For the third case, you must configure the corresponding device in file inittab.
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For the fourth case, you must configure the router and the Unix server to use
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the same application mode.
Terminal echoing speed is low
Use the ttyd administration program to check the system resource occupation rate
of the Unix server. If the rate is relatively high, locate which service process is
abnormal and, if necessary, kill the process.
If the rate is not high, open the ttyd configuration file to examine whether the
sendsize and readsize options are properly configured. For low speed WAN links
(at 9,600 bps for example), the two options must be modified accordingly.
In addition, for higher terminal echoing speed, one-to-one mode is recommended.
The terminal displays abnormally for some banking services
Some banking services require certain types of terminal emulation. Terminal
emulation type is configured for each pseudo terminal in system file /etc/ttytype
on the Unix server. When upgrading network devices, if you modify pseudo
terminal numbers, you must edit the system file to add terminal emulation types
for the new pseudo terminals. Taking ttyp50 as an example, you must add the
following line to the file /etc/ttytype:
vt100 ttyp50
If a pseudo terminal is configured with no terminal emulation type in file
/etc/ttytype on the Unix server, the pseudo terminal uses the default emulation
type unknown, and the prompt message at login "TERM = (unknown)" displays.
Some pseudo terminals cannot be opened
After ttyd is started, if the log does not prompt that a terminal is open, the
terminal is not open. Check the configuration file to see whether the terminal is
given a valid name.
Terminal Access Troubleshooting 811