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Re: Reverse telnet question posted 09/28/2006
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Hi Dave,
   
  actually reverse telnet doesn't do anything with Telneting to another router.
   
  it is just the connection made via the router's TTY to another router's console, this way we can reach another router's console connected to the TTY line.
   
  TerminalServer#show host
Default domain is not set
Name/address lookup uses static mappings
  Codes: UN - unknown, EX - expired, OK - OK, ?? - revalidate
       temp - temporary, perm - permanent
       NA - Not Applicable None - Not defined
  Host                      Port  Flags      Age Type   Address(es)
BB1                       2065  (perm, OK)  0   IP    1.1.1.1
SW1                       2074  (perm, OK)  0   IP    1.1.1.1
SW2                       2075  (perm, OK)  0   IP    1.1.1.1
PIX                       2076  (perm, OK)  0   IP    1.1.1.1
R4                        2069  (perm, OK)  0   IP    1.1.1.1
R2                        2067  (perm, OK)  0   IP    1.1.1.1
R3                        2068  (perm, OK)  0   IP    1.1.1.1
R1                        2066  (perm, OK)  0   IP    1.1.1.1
R6                        2071  (perm, OK)  0   IP    1.1.1.1
R5                        2070  (perm, OK)  0   IP    1.1.1.1
BB2                       2072  (perm, OK) 49   IP    1.1.1.1
BB3                       2073  (perm, OK) **   IP    1.1.1.1
TerminalServer#show line
   Tty Typ     Tx/Rx    A Modem  Roty AccO AccI   Uses   Noise  Overruns   Int
     0 CTY              -    -      -    -    -     10       0     0/0       -
*   65 TTY   9600/9600  -    -      -    -    -      5      16     0/0       -
*   66 TTY   9600/9600  -    -      -    -    -     38    5181     0/0       -
    67 TTY   9600/9600  -    -      -    -    -     16   21262     0/0       -
*   68 TTY   9600/9600  -    -      -    -    -     41   42578     0/0       -
*   69 TTY   9600/9600  -    -      -    -    -     25    3165     0/0       -
*   70 TTY   9600/9600  -    -      -    -    -     28     208     0/0       -
*   71 TTY   9600/9600  -    -      -    -    -     21   59258     0/0       -
    72 TTY   9600/9600  -    -      -    -    -      5  268756     0/0       -
    73 TTY   9600/9600  -    -      -    -    -      0       0     0/0       -
*   74 TTY   9600/9600  -    -      -    -    -     20    1555 20515/61650   -
*   75 TTY   9600/9600  -    -      -    -    -     26    1926  3199/9635    -
*   76 TTY   9600/9600  -    -      -    -    -     19     122     0/0       -
    77 TTY   9600/9600  -    -      -    -    -      0       0     0/0       -
    78 TTY   9600/9600  -    -      -    -    -      0       0     0/0       -
    79 TTY   9600/9600  -    -      -    -    -      0       0     0/0       -
    80 TTY   9600/9600  -    -      -    -    -      0       0     0/0       -
   129 AUX 115200/115200- inout     -    -    -     42       0  1837/0       -
*  130 VTY              -    -      -    -    -    263       0     0/0       -
*  131 VTY              -    -      -    -    -     92       0     0/0       -
   132 VTY              -    -      -    -    -      3       0     0/0       -
   133 VTY              -    -      -    -    -      0       0     0/0       -
   134 VTY              -    -      -    -    -      0       0     0/0       -
   
  the asterisk (*) means that the line is currently being used.
   
  in this example, reverse telneting to R3 (Port 2068, line 68) will fail because the line is currently being used.
   
  TerminalServer#R3
Trying R3 (1.1.1.1, 2068)... 
% Connection refused by remote host
   
  and reverse telneting to BB2 (Port 2072, line 72) will succeed because the line is currently available.
   
  TerminalServer#BB2
Trying BB2 (1.1.1.1, 2072)... Open
  
User Access Verification
  Username: tom
Password: 
   
  if you issue show tcp brief on the terminal server, the output will be something like this :
   
  BB2# 
  TerminalServer#show tcp brief
TCB       Local Address           Foreign Address        (state)
61DBBC6C  1.1.1.1.32387                1.1.1.1.2072                ESTAB
61DBCC34  1.1.1.1.2072                  1.1.1.1.32387               ESTAB
   
  from the output, we can see that the Foreign Address is the Terminal Server router itself. 
   
  if you plan to build a terminal server you can use NM-8A, NM-16A on new platform or using the old 2511 router.
  TerminalServer#show diag
Slot 2:
        Async Port adapter, 16 ports
        Port adapter is analyzed 
        Port adapter insertion time unknown
        EEPROM contents at hardware discovery:
        Hardware revision 0.1           Board revision L0
        Serial number     33541801      Part number    800-02244-05
        FRU Part Number:  NM-16A=
          Test history      0x0           RMA number     00-00-00
        EEPROM format version 1
        EEPROM contents (hex):
          0x20: 01 62 00 01 01 FF CE A9 50 08 C4 05 00 00 00 00
          0x30: A8 00 00 00 05 05 06 00 FF FF FF FF FF FF FF FF
   
  HTH and CMIIW
   
  thanks
   
  Rgds,
  Thomwin

"Schulz, Dave" <DSchulz@xxxxxxxxxxxxxx> wrote:
  I am unable to get the following reverse telnet to work .....

R1 has the following set up on the vty....

!
!
line con 0
line aux 0
line vty 0 4
privilege level 15
password cisco
login
rotary 1
!
R1(config)#do sh line
Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns
Int
* 0 CTY - - - - - 4 407 0/0
-
129 AUX 9600/9600 - - - - - 0 0 0/0
-
130 VTY - - 1 - - 1 0 0/0
-
131 VTY - - 1 - - 0 0 0/0
-
132 VTY - - 1 - - 0 0 0/0
-
133 VTY - - 1 - - 0 0 0/0
-
134 VTY - - 1 - - 0 0 0/0
-


On R3.... I am trying to telnet to the first vty port (or any of them).
This is the response:


R3#
R3#telnet 172.16.1.1 2130
Trying 172.16.1.1, 2130 ...
% Connection refused by remote host

R3#

However, telnetting in to the unit without selecting the port works
fine. Any thoughts?


Dave Schulz,

Email: dschulz@xxxxxxxxxxxxxx 

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