Saturday, September 14, 2013

Configure Syslog and Debug Facility on an ASA

Most issues with remote management access appears in the ASA system logs (or to a remote syslog server). Use the show logging command or the ASDM real-time log viewer in order to examine the log files on the ASA.

ciscoasa(config)# logging ?

configure mode commands/options:
  asdm                      Set logging level or list for ASDM
  asdm-buffer-size          Specify ASDM logging buffer size
  buffer-size               Specify logging memory buffer size
  buffered                  Set buffer logging level or list
  class                     Specify logging event class
  console                   Set console logging level or list
  debug-trace               Enable logging of redirect debug-trace output to
                            syslog
  device-id                 Specify the device-id to be included in all
                            non-EMBLEM formatted syslog messages
  emblem                    Enable logging Emblem format on all output
                            supported destinations
  enable                    Enable logging to all output supported destinations
  facility                  Specify the syslog facility, the default is 20
  flash-bufferwrap          Save logging buffer to flash when buffer
                            wrap-around
  flash-maximum-allocation  Specify logging maximum flash space allocation
  flash-minimum-free        Specify logging minimum flash free space threshold
  flow-export-syslogs       Enable/Disable syslogs whose information is
                            captured by NetFlow
  from-address              Specify the from address for the mail logging
  ftp-bufferwrap            Save logging buffer using FTP when buffer
                            wrap-around
  ftp-server                Specify FTP server parameters
  history                   Set the SNMP message level or list for sending
                            syslog traps
  host                      Send syslog messages to a host
  list                      Specify logging event list
  mail                      Set mail logging level or list
  message                   Specify a message to be allowed
  monitor                   Specify that syslog messages appear on Telnet
                            sessions to the Firewall console
  permit-hostdown           Allow new connection even if TCP syslog server is
                            down
  queue                     Specify queue size for storing syslog messages,
                            default is 512, 0 means unlimited (subject to
                            available memory)
  rate-limit                Specify logging rate-limit parameters
  recipient-address         Specify the mail logging recipient address and
                            level
  standby                   Enable logging on standby unit with failover
                            enabled, warning: this option causes twice as much
                            traffic on the syslog server
  timestamp                 Enable logging timestamp on syslog messages
  trap                      Set logging level or list for syslog server

exec mode commands/options:
  savelog  Save logging buffer to flash

ciscoasa(config)# logging enable
ciscoasa(config)# logging buffered  ?

configure mode commands/options:
  <0-7>          Enter syslog level (0 - 7)
  WORD           Specify the name of logging list
  alerts         Immediate action needed           (severity=1)
  critical       Critical conditions               (severity=2)
  debugging      Debugging messages                (severity=7)
  emergencies    System is unusable                (severity=0)
  errors         Error conditions                  (severity=3)
  informational  Informational messages            (severity=6)
  notifications  Normal but significant conditions (severity=5)
  warnings       Warning conditions                (severity=4)
ciscoasa(config)# logging buffered debugging
ciscoasa(config)#
%ASA-5-111008: User 'enable_15' executed the 'logging buffered debugging' command.
%ASA-5-111010: User 'enable_15', running 'CLI' from IP 0.0.0.0, executed 'logging buffered debugging'
ciscoasa(config)# show logging
Syslog logging: enabled
    Facility: 20
    Timestamp logging: disabled
    Standby logging: disabled
    Debug-trace logging: disabled
    Console logging: disabled
    Monitor logging: disabled
    Buffer logging: level debugging, 2 messages logged
    Trap logging: disabled
    Permit-hostdown logging: disabled
    History logging: disabled
    Device ID: disabled
    Mail logging: disabled
    ASDM logging: disabled


If you wish to log all messages from all severity levels, it is strongly recommended that you do so to the internal buffer, and never to the console. In fact, it is generally recommended to leave console logging disabled.

The Cisco ASDM also contains a powerful event viewer that you can use to display a real-time messages from the ASA. This event viewer is particularly useful when you are troubleshooting ASA software and configuration issues, or when you are monitoring real-time activity over the ASA.

You enable logging to the internal ASDM event viewer by configuring the ASDM logging destination and specifying a logging filter, in the same manner as for other logging destinations.

ciscoasa(config)# logging asdm ?

configure mode commands/options:
  <0-7>          Enter syslog level (0 - 7)
  WORD           Specify the name of logging list
  alerts         Immediate action needed           (severity=1)
  critical       Critical conditions               (severity=2)
  debugging      Debugging messages                (severity=7)
  emergencies    System is unusable                (severity=0)
  errors         Error conditions                  (severity=3)
  informational  Informational messages            (severity=6)
  notifications  Normal but significant conditions (severity=5)
  warnings       Warning conditions                (severity=4)
ciscoasa(config)# logging asdm informational







If the syslog messages don't pinpoint the issue, consider debugging management protocols on the ASA, such as the following:

* debug ssh: Debugs the SSH daemons to determine low-level protocol failures, such as algorithm or version incompatibility.

* debug http: Debugs HTTP exchanges to determine problems with the ASDM image.

* debug snmp: Debugs SNMP exchanges to help determine problems with SNMP authentication and OIDs.

ciscoasa# debug ssh ?

  <1-255>  Specify an optional debug level (default is 1)
  <cr>
ciscoasa# debug ssh
debug ssh  enabled at level 1
%ASA-5-111008: User 'enable_15' executed the 'debug ssh' command.
ciscoasa#
%ASA-6-302013: Built inbound TCP connection 1304 for management:10.1.1.10/3919 (10.1.1.10/3919) to identity:10.1.1.1/22 (10.1.1.1/22)
%ASA-3-315004: Fail to establish SSH session because RSA host key retrieval failed.
%ASA-6-315011: SSH session from 10.1.1.10 on interface management for user "" disconnected by SSH server, reason: "Internal error" (0x00)
Device ssh opened successfully.
SSH0: SSH client: IP = '10.1.1.10'  interface # = 2
SSH: unable to retrieve default host public key.  Please create a defauth RSA key pair before using SSH
SSH0: Session disconnected by SSH server - error 0x00 "Internal error"
%ASA-6-302014: Teardown TCP connection 1304 for management:10.1.1.10/3919 to identity:10.1.1.1/22 duration 0:00:00 bytes 0 TCP FINs

ciscoasa# debug http
debug http enabled at level 1.
ciscoasa# %ASA-5-111008: User 'enable_15' executed the 'debug http' command.
%ASA-5-111010: User 'enable_15', running 'CLI' from IP 0.0.0.0, executed 'debug http'
ciscoasa#
%ASA-3-710003: TCP access denied by ACL from 10.1.1.10/3966 to management:10.1.1.1/443
%ASA-7-710005: TCP request discarded from 10.1.1.10/3966 to management:10.1.1.1/443
%ASA-3-710003: TCP access denied by ACL from 10.1.1.10/3966 to management:10.1.1.1/443
%ASA-7-710005: TCP request discarded from 10.1.1.10/3966 to management:10.1.1.1/443


Finally, you can also troubleshoot possible issues between an ASA and a remote AAA server by using the debug tacacs or debug radius commands. You can specify conditional debugging (such as limiting to a single username) to avoid excessive output and performance issues.

ciscoasa# debug aaa ?

  accounting
  authentication
  authorization
  common
  internal
  shim
  <cr>
ciscoasa# debug aaa authentication
debug aaa authentication enabled at level 1
ciscoasa# %ASA-5-111008: User 'enable_15' executed the 'debug aaa authentication' command.
ciscoasa# exit

Logoff

Username: %ASA-5-611103: User logged out: Uname: enable_15

Username: cisco
Password: *****
%ASA-6-113015: AAA user authentication Rejected : reason = Invalid password : local database : user = cisco
%ASA-6-611102: User authentication failed: Uname: cisco
%ASA-6-605004: Login denied from serial to console for user "cisco"
Username: John
Password: *****
%ASA-6-113012: AAA user authentication Successful : local database : user = John
%ASA-6-113008: AAA transaction status ACCEPT : user = John
Type help or '?' for a list of available commands.
%ASA-6-611101: User authentication succeeded: Uname: John
%ASA-6-605005: Login permitted from serial to console for user "John"
ciscoasa> enable
Password: 
ciscoasa# %ASA-5-502103: User priv level changed: Uname: enable_15 From: 1 To: 15

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