I have configured a Cisco 2911 with an HWIC-1T card as a terminal server using the configuration below. I can telnet to port 2003 of the loopback address and establish a serial connection to a laptop connected to the HWIC-1T card.
interface serial 0/0/0 physical-layer async no ip address encapsulation slip line 0/0/0 no exec transport input telnet transport output none
The stream of characters going from the serial connection to the telnet session works perfectly. However, the stream of characters going from the telnet session out to the serial connection to the laptop lags one character behind most of the time.
Meaning if I type "1234" into the telnet window, I will see just "123" come out the serial window. The last character isn't lost, just buffered in the router until I press the next key. Sometimes the router will buffer two characters and sometimes if I type two characters together in quick sessesion, both will be correctly displayed.
I know the router is doing the buffering because I ran Wireshark and saw the TCP packet with the last character enter the router and not immediately get displayed.
What am I doing wrong? Thanks in advance!