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ASR9000/XR: How to reset a lost password (password recovery on IOS-XR)

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Introduction

This document shows you how to reset a lost password or when you have locked yourself out due to a problematic AAA configuration.

 

Core Issue

Because IOS-XR is substantially different in the way config files are managed, the standard trick of conf-reg 0x2142 will not work for IOS-XR.

You can lock yourself out if you are configuring aaa authentication to tacacs with no local fall back, if the tacacs server is unavailable there

is no way for you to get in.

 

eg:

aaa authentication login default groupt tacacs

 

Also this procedure is good when you have forgotten the password to your super user in IOS-XR to manage your machine.

 

Resolution

 

The following step through guide can be tried, the details of each step are listed below with more explanation:

 

  • •1)       Fixing AAA configuration errors  
    • •a.       On the standby RP/RSP from the CONSOLE port hit the ESC key and type ‘ksh’ without quotes and hit ENTER  
      • i.      Login with a local username and password
      • ii.      If this fails get the standby RP/RSP into ROMMON
      • iii.      Bypass KSH authentication with AUX_AUTHEN_LEVEL=0 and boot
      • iv.      Try step 1a again or use the AUX port and go to step 1b
    • •b.       View and edit the configuration from KSH  
      • i.      Save the configuration to harddisk with ‘nvgen -c -l 1 -t 1 -o 1  > harddisk:/backupconfig.txt’
      • ii.      Edit out the bad AAA statements with ‘nano –e /harddisk:/backupconfig.txt’
    • •c.        Try to roll back the configuration with ‘config_rollback –n 0x1’
    • •d.       Bypass AAA and enter exec mode with ‘/pkg/bin/exec –a’
    • •e.        Attempt to use show commands or change the configuration 
      • i.      If this fails reload all RP/RSP ROMMON
      • ii.      On the standby card set IOX_CONFIG_FILE=/harddisk:/backupconfig.txt or use ‘boot <image> -a <bogus_config>’ and boot
      • iii.      Also follows step 2g if you saw issues in 1a
      • iv.      If nothing above worked then this is the only option
  • •2)       Fixing a lost local username/password  
    • •a.       Get the standby RP/RSP into ROMMON  
      • i.      Bypass KSH authentication with AUX_AUTHEN_LEVEL=0 and boot
    • •b.       View the admin configuration with ‘nvgen –b /admin/cfg’
    • •c.        Save the admin configuration to the harddisk and edit out any and all users if you need other portions of this file
    • •d.       Bypass AAA and enter exec mode with ‘/pkg/bin/exec –a’
    • •e.        Attempt to use show commands or change the configuration
    • •f.        If this fails reload all RP/RSP to ROMMON
    • •g.        Set confreg 0x142 or IOX_ADMIN_CONFIG_FILE=/harddisk:/backupconfig.txt on the standby card or ‘boot <image> -o <bogus_config>’ and boot  
      • i.      Note that this does not ignore the exec configuration and will not help if the issue is AAA related
    • •h.       Enter a new username and password when prompted
  • •3)       Fixing both issues 
    • •a.       If you do not know a local login or cannot use the KSH method to recover the configuration then both the IOX_CONFIG_FILE and IOX_ADMIN_CONFIG_FILE will need to be pointed towards non-existent files. Both the admin and exec configurations will be cleared by this method
  • •4)       Make sure to remove any ROMMON variables which were change
  • 5)  XR-VM Username/Password reset procesdure using Sysadmin VM

 

There are 2 steps to this process.

1) Override the BASE running configuration

     When you configure the problematic AAA statement sample as above.

2) Override the admin configuration that stores local usernames and passwords

     When you don't remember any of the local usernames/passwords you have defined locally.

Overriding the Base configuration in XR:

 

Step 1

In rommon set the following variable:

 

rommon> IOX_CONFIG_FILE=/harddisk:/no-config

 

the file no-config is just a non existent file, you can give any name here really.

 

Note: This ROMMON variable will persist and needs to be removed after password recovery. Check the 'clean up' section.

 

 

Step 2

And issue 'sync', this will make the change persistent in the rommon config vars.

 

rommon> sync

 

Step 3

Issue 'i' or 'reset' and when the rsp is booting up, it should ignore  the config file, since there's no config file found on /harddisk:  called no-config

 

rommon> reset

or

rommon> i

 

 

Overriding the ADMIN configuration in XR:

In Admin configuration we store all the local usernames and passwords.

Step 1

 

Similarly you can do the same thing for admin config:

 

IOX_ADMIN_CONFIG_FILE=/disk0:/none

 

You should get prompted for root user/pass and will have a blank config on the box.

You need to load your config and do your modification.

 

Note: This ROMMON variable will persist and needs to be removed after password recovery. Check the 'clean up' section.

Step 2 and 3

are the same as for the base xr config file.

 

Second Option

 

Another way of recoveryof the password is to enable the following again in rommon:

 

rommon> AUX_AUTHEN_LEVEL=0

 

Which will allow the aux port to drop to ksh upon the RSP bootup with no prompt for login.

 

At the prompt you can either type:

 

/pkg/bin/exec -a

 

Which will give you a router prompt: Or simply

 

# Config

 

Which drops you into EXEC config mode.

Example

# uname -a

QNX node0_RSP0_CPU0 6.4.0 2009/12/10-13:43:22PST asr9k ppcbe

# config

RP/0/RSP0/CPU0:RO-A(config)#exit

#

# /pkg/bin/exec -a

RP/0/RSP0/CPU0:RO-A#

RP/0/RSP0/CPU0:RO-A#

RP/0/RSP0/CPU0:RO-A#exit

#

Clean up

Make sure that after you're done with your changes, in case you made the rommon vars persistent, you may want to unset

the variables to get back to the normal files that are used.

 

rommon> unset IOX_ADMIN_CONFIG_FILE

rommon> unset IOX_CONFIG_FILE

rommon> sync

 

All set!

 

If you forget the cleanup, you might see these lines:

 

RP/0/RSP1/CPU0:Oct 28 07:18:37.141 : locald_DSC[301]: %SECURITY-LOCALD-3-LWA_ADD_FAIL : Failed to add the username admin to lightweight authentication password database: No such file or directory

 

Another way to clear the variable:

more nvram:/classic-rommon-var  location 0/RSP1/CPU0

run iox_on 0/RSP1/CPU0 nvram_rommonvar IOX_CONFIG_FILE ""

Step 5


XR-VM Username/Password reset procedure using Sysadmin VM

 

Note: This is not a process to hack router but user need sysadmin username / password for the accessibility of box by bypass XR credentials.

Steps to perform this activity:

1. login to router : I was having console access to the box.

bgl-xdm-009:112> telnet 10.67.30.20 2037
Trying 10.67.30.20...
Connected to 10.67.30.20.
Escape character is '^]'.


User Access Verification

Password:
Password OK

2. Pass interrupts "ctrl + o" to toggle to sysadmin

sysadmin-vm:0_RP0#
*** IDLE TIMEOUT ***

System Admin Username:

3. enter sysadmin username and password

System Admin Username: xxxxx

Password:

xxxxx connected from 127.0.0.1 using console on sysadmin-vm:0_RP0
sysadmin-vm:0_RP0#


4. with this login you can access "sysadmin- VM prompt"

sysadmin-vm:0_RP0#

5. From Sysadmin VM to access XR - VM perform following action

i. list sdr ips
sysadmin-vm:0_RP0# show sdr
Tue Apr 3 05:12:47.110 UTC

SDR: default-sdr
Location IP Address Status Boot Count Time Started
-----------------------------------------------------------------------------
0/RP0/VM1 192.0.0.4 RUNNING 1 03/01/2019 02:10:28
0/RP0/VM2 192.0.0.6 RUNNING 1 03/01/2019 02:10:56

ii. ssh SDR VM1 address

[sysadmin-vm:0_RP0:~]$ssh 192.0.0.4

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
<>
Last login: Fri Mar 1 02:14:39 2019 from 192.0.0.4

iii. Now you are at XR-VM and to disable credential pass "ctrl + a" interrupt

[xr-vm_node0_RP0_CPU0:~]$exec -a

6. After disabling credential you can access XR-VM

RP/0/RP0/CPU0:customer2#

at this stage you can create/ delete / modify user credentials to access router at XR-VM directly.

P/0/RP0/CPU0:customer2#show running-config
Tue Apr 3 05:13:02.445 UTC
Building configuration...
!! IOS XR Configuration version = 6.3.3
!! Last configuration change at Sun Feb 17 23:31:51 2019 by ZTP
!
hostname customer2 >>>
username asd
group root-lr
group cisco-support
secret 5 $1$rdaY$qJt7aNcc8uFKqhP/rK11V1
!

Related Information

It has been seen that sometimes a system autonomously enters password recovery mode. This is identified with:

“enter root-system username”

 

This is due to a ddts known as CSCth03923

You end up providing what you think is a known username and password combination and it failes to get you in.

The solution is simple, just enter a fake username/password that you know for sure has not been configured yet and you're in!

 

 

 

Xander Thuijs - CCIE #6775

Sr Tech Lead ASR9000

Comments
Cisco Employee

Hi Xander, Thank you for this document. But I saw there is another way to recover the password with setting config-register to 0x142. What is the difference between that with the way in this document?Thanks.

http://www.cisco.com/en/US/docs/routers/asr9000/software/rommon/configuration/guide/rmasr9kpswd.html

Cisco Employee

Unlike IOS, 0x142 will not ignore the configuration, but only ask you for a new root password at bootup.

So this will work for local authentication, but will not address a TACACS configuration/reachability issue (which is actually more frequent than just 'forgetting' the password).  In those cases you need to use the method described above.

Beginner

Hi,

     As a part of this discussion, please let me know if any one knows how to configure aging/expiry of passwords, the number of atttenpts of a password to logon in  ASR 9000 ??

Cisco Employee

Not inside XR, you would need a tacacs/radius server for that that can do profile management for failed auth attempts and pw expiry.

xander

Beginner

Hi Xander, Thank you for your reply.

              But, how about the passwords of local users?

Cisco Employee

Local user database doesn't have that capability.

xander

Beginner

Hi Xander,

                  Thanks for your infomation. I couldn't find "login local" command in line console of ASR9k. Is n't available in XR ? Where can we apply user user-name and password password in ASR ?

Cisco Employee

this is the precise command:

RP/0/RSP0/CPU0:A9K-BNG(config)#line console login authentication ?

  WORD     Use an authentication list with this name

  default  Use the default authentication list

Beginner

Hi Xander,

If we follow the below stepsm, will the router ask username and password? please suggest the right way if it's wrong.

(config)#aaa authentication login default group local

(config)#line console login authentication default

Cisco Employee

if you combine it with aaa authentication login default local, it  will use the local username and password dbase.

which is also nicely documented here btw: https://supportforums.cisco.com/docs/DOC-22848

It references another article in case you want to go hardcore  with "priv levels" and what have you.

cheers

xander

--------

Xander Thuijs CCIE #6775

Principal Engineer ASR9000

Beginner

Thank you  Xander.

Beginner

Hi Xander,

                    May I know how to configure a telnet connection in ASR 9k. Can we use template name for representing a number of vty lines ?

Cisco Employee

Tushar: you need to define a telnet server in the vrf that you want to accept sessions on:

eg:

telnet vrf default ipv4 server max-servers 4

the number "4" here identifies the number of vty's or simultenous telnet sessions you allow to accept.

these vty's are used for both telnet and ssh btw.

line template main purpose is for the console.

xander

Beginner

Hi Xander,

                Thanks Xander, Yeah, but when I searched , I got these steps. Here don't  they discribe about telnet configuration ?

Cisco Employee

the telnet ipv<x> server enables the telnet deamon and provides the number of vty's specified.

the vty-pool command applies a template of configuration to the vty's.

since you can't really control on which vty a telnet lands (first session uses vty 0, second number 1 etc),

there is little use of making different vty pools with different line template configuration if you ask me.

So base configuration would be:

aaa authorization exec default local

aaa authentication login default local

vty-pool default 0 4 line-template default

telnet vrf default ipv4 server max-servers 4

then you have room for 5 telnet sessions locally authetnicated.

xander

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