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Aruba Employee

Configuring a Comware router to act as a terminal server

Overview
It can be really useful to have direct serial port access to devices. In the case of network devices, this enables bare metal access, including access to the boot-loader, service OS, etc. This was typically provided using a dedicated terminal server. You can provide essentially the same functionality using one of the HPE MSR routers and the appropriate async serial ports.

Router Components
This is the list of hardware I have used to provide 8 ports of serial console access:

 

  • HPE MSR 3012
  • 8 port async module (SIC-8AS)
  • 8 port RJ45 cable

2018-02-15 07.17.37.jpg

2018-02-15 07.19.25.jpg

 

Router Configuration
Configuration is very straighforward. Only a few CLI commands are required when most options are left at default.

Before you start, determine what ports are available, and what their identifiers are. For this router, the relevant ports are Async 1/0 to Async 1/7, with index 16-23, TTY 17-24.

 

[MSR3012-line-tty18]dis line
  Idx  Type     Tx/Rx      Modem Auth  Int          Location
  16   TTY 17   9600       -     N     Asy1/0       0/0
  17   TTY 18   9600       -     N     Asy1/1       0/0
  18   TTY 19   9600       -     N     Asy1/2       0/0
  19   TTY 20   9600       -     N     Asy1/3       0/0
  20   TTY 21   9600       -     N     Asy1/4       0/0
  21   TTY 22   9600       -     N     Asy1/5       0/0
  22   TTY 23   9600       -     N     Asy1/6       0/0
  23   TTY 24   9600       -     N     Asy1/7       0/0
  32   TTY 33   9600       inout N     Ser2/0:0     0/0
  176  AUX 0    9600       -     N     Aux0         0/0

Configure the async ports 

 

interface Async1/0
 description Remote Serial 0 port 4016
 async-mode flow
 undo detect dsr-dtr
#
interface Async1/1
 description Remote Serial 0 port 4017
 async-mode flow
 undo detect dsr-dtr
#
interface Async1/2
 description Remote Serial 0 port 4018
 async-mode flow
 undo detect dsr-dtr
#
interface Async1/3
 description Remote Serial 0 port 4019
 async-mode flow
 undo detect dsr-dtr
#
interface Async1/4
 description Remote Serial 0 port 4020
 async-mode flow
 undo detect dsr-dtr
#
interface Async1/5
 description Remote Serial 0 port 4021
 async-mode flow
 undo detect dsr-dtr
#
interface Async1/6
 description Remote Serial 0 port 4022
 async-mode flow
 undo detect dsr-dtr
#
interface Async1/7
 description Remote Serial 0 port 4023
 async-mode flow
 undo detect dsr-dtr

Configure the TTY lines

 

line tty 17 24
 undo shell
 user-role network-operator
 ssh redirect enable

Testing
Connect a rollover cable to one of the async ports; take a note of the ID on the cable. In the example below, cable ID 7 equates to interface Async 0/7, TTY 24, index 23. Adding 4000 to the index is the port number to access the redirected port.

Start a terminal emulator (eg Putty or Tera Term) and enter the IP and port details: 10.20.30.12:4023

 

tera term ssh redirect.png

You will now have remote access to the console port of the device connected to that async port. When you log out, you will see the normal console port sign-out screen

 

reverse telnet putty serial.png

Session details are available with the following command. Note the Idx number (23 here) to match the configured async ports. (The other entry is a login to the console port of the router.)

<MSR3012>dis ssh server session
 UserPid  SessID Ver   Encrypt    State         Retries Serv    Username   Idx
 846      0      2.0   aes256-cbc Established   0       Stelnet admin      23
 848      0      2.0   aes256-cbc Established   0       Stelnet admin

 Notes

  • Regular ethernet cables don't work - you have to use a serial/rollover cable
  • You can connect to an async port even if nothing is physially connected to it, but you will get nothing other than the username/password prompt

 

Richard Litchfield
Network Solution Architect, HPE Aruba
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