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Cisco Model 2511 - Access Server

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If you bought a Cisco 2511 from me in 2012 see here.

Sample config file: Attach:ts1_20050909.txt



Model 2511: 1 Ethernet, 2 synchronous serial, 16 asynchronous serial

Configuring a Terminal/Comm Server

Cable pin-outs

The Cisco 2511 went EOL on July 1st 2009

Working with modem control on Cisco 2500

If you see this message when you telnet to the port:

(:code:) termserv2>telnet async3 Trying async3 (, 2003)... % Connection refused by remote host (:codeend:)

Try this command:

(:code:) termserv2>clear line tty 3 [confirm]



The try the telnet again:

(:code:) termserv2>telnet async3 Trying async3 (, 2003)... Open (:codeend:)

Reset the password

Notes are at

First plug a serial cable (usually purple or light blue in color) to the light blue console RJ-45 plug. Now connect a terminal or PC using the serial port this this cable. Connect to the port at 9600 baud. You should see

 User Access Verification


Power off the 2511 and then power it back on again

You will see initially...

 System Bootstrap, Version 11.0(10c)XB1, PLATFORM SPECIFIC RELEASE SOFTWARE (fc1)

Copyright (c) 1986-1997 by cisco Systems 2500 processor with 6144 Kbytes of main memory

Now hit the break key or send a break signal (how to do this is dependent on your terminal hardware or software you are using)

You should see

 Abort at 0x10CFB9C (PC)


Now type in at the ">" prompt

 >o/r 0x042

This will cause a configuration reset and the system will reboot. You will then be prompted for a --- System Configuration Dialog ---

--- System Configuration Dialog ---

Would you like to enter the initial configuration dialog? [yes/no]: 
% Please answer 'yes' or 'no'.
Would you like to enter the initial configuration dialog? [yes/no]: yes

At any point you may enter a question mark '?' for help.
Use ctrl-c to abort configuration dialog at any prompt.
Default settings are in square brackets '[]'.

Basic management setup configures only enough connectivity
for management of the system, extended setup will ask you
to configure each interface on the system

Would you like to enter basic management setup? [yes/no]: yes
Configuring global parameters:

  Enter host name [Router]: router 

  The enable secret is a password used to protect access to
  privileged EXEC and configuration modes. This password, after
  entered, becomes encrypted in the configuration.
  Enter enable secret: test

  The enable password is used when you do not specify an
  enable secret password, with some older software versions, and
  some boot images.
  Enter enable password: test
% Please choose a password that is different from the enable secret
  Enter enable password: test

  The virtual terminal password is used to protect
  access to the router over a network interface.
  Enter virtual terminal password: test
  Configure SNMP Network Management? [yes]: no

Current interface summary

Any interface listed with OK? value "NO" does not have a valid configuration

Interface                  IP-Address      OK? Method Status                Protocol
Ethernet0                  unassigned      NO  unset  up                    up      
Serial0                    unassigned      NO  unset  down                  down    

Enter interface name used to connect to the
management network from the above interface summary: Ethernet0

Configuring interface Ethernet0:
  Configure IP on this interface? [yes]: 
    IP address for this interface:
    Subnet mask for this interface [] : 
    Class C network is, 24 subnet bits; mask is /24

The following configuration command script was created:

hostname router
enable secret 5 $1$yErT$QxApQO7NNMlIfGmY4sU.60
enable password test
line vty 0 4
password test
no snmp-server
no ip routing

interface Ethernet0
no shutdown
ip address
interface Serial0
no ip address

[0] Go to the IOS command prompt without saving this config.
[1] Return back to the setup without saving this config.
[2] Save this configuration to nvram and exit.

Enter your selection [2]: 2
The enable password you have chosen is the same as your enable secret.
This is not recommended.  Re-enter the enable password.

Building configuration...
Use the enabled mode 'configure' command to modify this configuration.

Press RETURN to get started!

00:00:05: %LINK-3-UPDOWN: Interface Ethernet0, changed state to up
00:00:05: %LINK-3-UPDOWN: Interface Serial0, changed state to down
00:00:06: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state to up
00:00:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state to up
00:03:20: %LINK-5-CHANGED: Interface Serial0, changed state to administratively down
00:03:21: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
00:04:17: %SYS-5-RESTART: System restarted --
Cisco Internetwork Operating System Software 
IOS (tm) 2500 Software (C2500-I-L), Version 12.1(27b), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2005 by cisco Systems, Inc.
Compiled Tue 16-Aug-05 22:38 by pwade

Now you can telnet to the IP address you sue above and login to the router.


Some Cisco IOS commands can be found at

A sample configuration:


If you want to use the network then telnet to the router on it's assigned address from above. Enter the enable command to enter the User Exec Mode.

 Password: <enter enable password we set above>

Then enter the command "config t" to start entering IOS configuration commands. I usually do this from within a terminal emulator software and store the commands in a text document which I then copy and paste onto the terminal emulator after making the needed edits.

router#config t
Enter configuration commands, one per line.  End with CNTL/Z.
router(config)#no service single-slot-reload-enable
router(config)#service timestamps debug uptime
router(config)#service timestamps log uptime
router(config)#service password-encryption
router(config)#hostname router
router(config-line)#line aux 0
router(config-line)#line vty 0 4
router(config-line)# exec-timeout 15 0
router(config-line)# password test
router(config-line)# autocommand  menu hosts
router#write mem
Building configuration...
Building configuration...

<b>Note:</b> Some texts online say "copy running-config startup-config - copies saved config in running config (RAM) to NVRAM or "write memory" for IOS under ver.11"

Now I always had under IOS 11 so I am used to "write mem" and it works on the sample units I have which are 12.1(27b) so maybe it still works. The 2511's are EOL so I imagine they can't support much newer IOS then 12. YMMV.

Now test our configuration

router>menu hosts
Server "router"    Line 18    Terminal-type vt100    

'ctrl-shift-6' then 'x' will suspend a connection to a hosts' serial
console.  'disconnect' will disconnect and close that session.

    1          OpenVMS host vax02
    2          Sun host Venus
    3          Sun host Mars
    4          linux host Orion
    5          async5
    6          intel-pc-22
    7          intel-pc-23
    8          Sun storage array controller - sun-1237-ne
    9          Sun storage array controller - sun-1245-ne
    10         async10
    11         async11
    12         async12
    13         async 13
    14         async 14
    15         async15
    16         async16
    17         Basic troubleshooting
    18         Exit to command line



 ts> telnet async1
 Trying async1 (, 2001)... 
 % Connection refused by remote host

This is often the result of a stuck line either by the remote device keeping it closed with a lack of EIA-232 pins being asserted (CTS/RTS for hardware flow control) or someone else was/is using the line. In either case you can clear the line by issuing:

 ts> clear line 1

You might need to clear the line a few times before it completely clears depending on the trouble.

Sending break signal from 2411 to a server like a Sun server:


Configure the 2511 with something like

 line 1 16
 telnet break-on-ip

And then send a 'telnet break' which the 2511 will then translate into a hardware break.

Using Sun's telnet client you'd do that with the sequence "^] send break" (ie. ^] to escape back to the telnet command prompt and then the command send break sends a telnet break.

If you are using the built in telnet command from within the IOS itself such as "telnet async 1" use control-shift-6 during the telnet session and the following sub-commands after hitting control-shift-6 are available to you (I did a ? to get this list):

 [Special telnet escape help]
  ^^B  sends telnet BREAK
  ^^C  sends telnet IP
  ^^H  sends telnet EC
  ^^O  sends telnet AO
  ^^T  sends telnet AYT
  ^^U  sends telnet EL

So for a break to halt a a Sun box enter at the keyboard "control-shift-6" and then quickly enter the "Ctrl-^ B". For example:



Set up NTP if you can

 ts> enable
 ts#config t 
 Enter configuration commands, one per line.  End with CNTL/Z.
 Building configuration...
 ts#show ntp associations detail configured, our_master, sane, valid, stratum 3
 ref ID, time D28B4D5A.DE4C4E89 (14:51:06.868 UTC Thu Dec 8 2011)
 our mode client, peer mode server, our poll intvl 64, peer poll intvl 64
 root delay 56.12 msec, root disp 76.22, reach 377, sync dist 106.689
 delay 4.49 msec, offset 0.1185 msec, dispersion 0.17
 precision 2**23, version 3
 org time D28B54BC.F1EE2083 (15:22:36.945 UTC Thu Dec 8 2011)
 rcv time D28B54BC.F2AD73B6 (15:22:36.947 UTC Thu Dec 8 2011)
 xmt time D28B54BC.F149D2CF (15:22:36.942 UTC Thu Dec 8 2011)
 filtdelay =     5.37    4.68    4.49    5.36    5.36    4.68    4.70    8.16
 filtoffset =   -0.23    0.08    0.12   -0.29   -0.32   -0.02   -0.03   -1.80
 filterror =     0.02    0.03    0.05    0.06    0.08    0.09    0.11    0.12

Then set the clock manually:

 #show clock
 *01:49:06.723 UTC Tue Mar 9 1993
 #clock set 10:17:15 08 dec 2011
 #show clock
 .10:17:18.599 UTC Thu Dec 8 2011

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Page last modified on January 23, 2016, at 04:53 AM EST