Cisco IPS 4200 Series Sensors

Configuring IDS Blocking Using VMS IDS MC

Document ID: 46743

Updated: Jun 16, 2008



This document provides a sample for the configuration of the Cisco Intrusion Detection System (IDS) via the VPN/Security Management Solution (VMS), IDS Management Console (IDS MC). In this case, Blocking from the IDS Sensor to a Cisco router is configured.



Before you configure Blocking, ensure you have met these conditions.

  • The Sensor is installed and configured for sensing necessary traffic.

  • The sniffing interface is spanned to the router outside interface.

Components Used

The information in this document is based on these software and hardware versions.

  • VMS 2.2 with IDS MC and Security Monitor 1.2.3

  • Cisco IDS Sensor 4.1.3S(63)

  • Cisco Router running Cisco IOS® Software Release 12.3.5

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.


For more information on document conventions, see the Cisco Technical Tips Conventions.


In this section, you are presented with the information to configure the features described in this document.

Note: To find additional information on the commands used in this document, use the Command Lookup Tool (registered customers only) .

Network Diagram

This document uses the network setup shown in this diagram.



This document uses the configurations shown here.

Router Light
Current configuration : 906 bytes
version 12.3
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
hostname light
enable password cisco
username cisco password 0 cisco
ip subnet-zero
ip ssh time-out 120
ip ssh authentication-retries 3
call rsvp-sync
fax interface-type modem
mta receive maximum-recipients 0
controller E1 2/0
interface FastEthernet0/0
 ip address
 duplex auto
 speed auto
interface FastEthernet0/1
 ip address
 duplex auto
 speed auto
interface BRI4/0
 no ip address
interface BRI4/1
 no ip address
interface BRI4/2
 no ip address
interface BRI4/3
 no ip address
ip classless
ip route
ip http server
ip pim bidir-enable
dial-peer cor custom
line con 0
line 97 108
line aux 0
line vty 0 4

Router House
Building configuration...

Current configuration : 797 bytes
version 12.3
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
hostname House
logging queue-limit 100
enable password cisco
ip subnet-zero
no ip domain lookup
interface Ethernet0
 ip address
 hold-queue 100 out
interface Ethernet1
 ip address

!--- After Blocking is configured, the IDS Sensor 
!--- adds this access-group ip access-group. 

IDS_Ethernet1_in_0 in
ip classless
ip route
ip route
ip http server
no ip http secure-server

!--- After Blocking is configured, the IDS Sensor
!--- adds this access list.

ip access-list extended IDS_Ethernet1_in_0.
 permit ip host any
 permit ip any any
line con 0
 stopbits 1
line vty 0 4
 password cisco
scheduler max-task-time 5000

Initial Sensor Configuration

Complete these steps to initially configure the Sensor.

Note: If you have performed the initial setup of your Sensor, proceed to the section Importing the Sensor into IDS MC.

  1. Console into the Sensor.

    You are prompted for a username and password. If this is the first time you are consoling into the Sensor, you must login with the username cisco and password cisco.

  2. You are prompted to change the password and then re-type the new password to confirm.

  3. Type setup and enter the appropriate information at each prompt to set up basic parameters for your Sensor, as per this example:

        --- System Configuration Dialog --- 
    At any point you may enter a question mark '?' for help. 
    User ctrl-c to abort configuration dialog at any prompt. 
    Default settings are in square brackets '[]'. 
    Current Configuration: 
    hostname sensor5 
    telnetOption enabled 
    accessList ipAddress netmask 
    active-selection none 
    service webServer 
    ports 443 
  4. Press 2 in order to save your configuration.

Import the Sensor into IDS MC

Complete these steps to import the Sensor into the IDS MC.

  1. Browse to your Sensor.

    In this case, browse to either or

  2. Login with the appropriate username and password.

    In this example, the username admin and password cisco were used.

  3. Select VPN/Security Management Solution > Management Center and choose IDS Sensors.

  4. Click the Devices tab, select Sensor Group, highlight Global, and click Create Subgroup.

  5. Enter the Group Name and ensure the Default radio button is selected, then click OK to add the subgroup into the IDS MC.


  6. Select Devices > Sensor, highlight the subgroup created in the previous step (in this case, test), and click Add.

  7. Highlight the subgroup, and click Next.


  8. Enter the details as per this example, then click Next to continue.


  9. After you are presented with a message that states Successfully imported sensor configuration, click Finish to continue.


  10. Your Sensor is imported into the IDS MC. In this case, sensor5 is imported.


Import the Sensor into Security Monitor

Complete this procedure to import the Sensor into the security monitor.

  1. At the VMS Server menu, select VPN/Security Management Solution > Monitoring Center > Security Monitor.

  2. Select the Devices tab, then click Import and enter the IDS MC Server Information, as per this example.


  3. Select your Sensor (in this case, sensor5) and click Next to continue.


  4. If need be, update the Network Address Translation (NAT) address for your Sensor, then click Finish to continue.


  5. Click OK to finish importing the Sensor from IDS MC into Security Monitor.


  6. Your Sensor is successfully imported.


Use IDS MC for Signature Updates

Complete this procedure to use the IDS MC for signature updates.

  1. Download the Network IDS Signature updates (registered customers only) from the Downloads and save them in the C:\PROGRA~1\CSCOpx\MDC\etc\ids\updates\ directory on your VMS server.

  2. At the VMS server console, select VPN/Security Management Solution > Management Center > Sensors.

  3. Click the Configuration tab, select Updates, and click Update Network IDS Signatures.

  4. Select the signature you want to upgrade from the drop-down menu and click Apply to continue.


  5. Select the Sensor(s) to update, and click Next to continue.


  6. After you are prompted to apply the update to the Management Center, as well as the Sensor, click Finish to continue.


  7. Telnet or console into the Sensor command line interface. Information similar to this appears:

    Broadcast message from root (Mon Dec 15 11:42:05 2003): 
    Applying update IDS-sig-4.1-3-S63.  
    This may take several minutes. 
    Please do not reboot the sensor during this update. 
    Broadcast message from root (Mon Dec 15 11:42:34 2003): 
    Update complete. 
    sensorApp is restarting 
    This may take several minutes. 
  8. Wait for a few minutes to allow the upgrade to complete, then enter show version to verify.

    sensor5#show version 
    Application Partition: 
    Cisco Systems Intrusion Detection Sensor, Version 4.1(3)S63 
    Upgrade History: 
    * IDS-sig-4.1-3-S62           07:03:04 UTC Thu Dec 04 2003 
       IDS-sig-4.1-3-S63.rpm.pkg   11:42:01 UTC Mon Dec 15 2003 

Configure Blocking for the IOS Router

Complete this procedure to configure Blocking for the IOS router.

  1. At the VMS server console, select VPN/Security Management Solution > Management Center > IDS Sensors.

  2. Select the Configuration tab, select your Sensor from Object Selector, and click Settings.

  3. Select Signatures, click Custom, then click Add to add a new signature.


  4. Enter the new Signature Name, then select the Engine (in this case, STRING.TCP).

  5. You can customize the available parameters by checking the appropriate radio button and clicking Edit.

    In this example, the ServicePorts parameter is edited to change its value to 23 (for port 23). The RegexString parameter is also edited to add the value testattack. When this is complete, click OK to continue.


  6. To edit the Signature Severity and Actions or to Enable/Disable the signature, click the name of the signature.


  7. In this case, the severity is changed to High and the Block Host action is selected. Click OK to continue.

    • The Block Host blocks attacking IP hosts or IP subnets.

    • The Block Connection blocks TCP or UDP ports (based on attacking TCP or UDP connections).


  8. The complete signature looks similar to this:


  9. In order to configure the Blocking Device, select Blocking > Blocking Devices from the Object Selector (the menu on the left hand side of the screen), and click Add to enter the following information:


  10. Click Edit Interfaces (see previous screen capture), click Add, enter this information, then click OK to continue.


  11. Click OK twice to complete the configuration of the Blocking device.


  12. To configure Blocking Properties, select Blocking > Blocking Properties.

    The Length of Automatic Block can be modified. In this case, it is changed to 15 minutes. Click Apply to continue.


  13. Select Configuration from the main menu, then select Pending, check the pending configuration to ensure it is correct, and click Save.


  14. To push the configuration changes to the Sensor, generate and then deploy the changes by selecting Deployment > Generate and click Apply.


  15. Select Deployment > Deploy, then click Submit.

  16. Check the checkbox next to your Sensor, then click Deploy.

  17. Check the checkbox for the job in the queue, then click Next to continue.


  18. Enter the Job Name and schedule the job as Immediate, then click Finish.


  19. Select Deployment > Deploy > Pending.

    Wait a few minutes until all the pending jobs have been completed. The queue is then empty.

  20. To confirm the deployment, select Configuration> History.

    Ensure the status of the configuration is displayed as Deployed. This means that the Sensor configuration has been updated successfully.



This section provides information you can use to confirm your configuration is working properly.

Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.

Launch the Attack and Blocking

To verify that the Blocking process is working correctly, launch a test attack and check the results.

  1. Before launching the attack, select VPN/Security Management Solution > Monitoring Center > Security Monitor.

  2. Choose Monitor from the main menu, click Events and then click Launch Event Viewer.


  3. Telnet to the router (in this case, Telnet to the House router), to verify the communication from the Sensor.

    house#show user 
        Line       User       Host(s)              Idle       Location 
    *  0 con 0                idle                 00:00:00 
     226 vty 0                idle                 00:00:17 
    house#show access-list 
    Extended IP access list IDS_Ethernet1_in_0 
        10 permit ip host any 
        20 permit ip any any (20 matches) 
  4. To launch the attack, Telnet from one router to the other and type testattack.

    In this case, we used Telnet to connect from the Light router to the House router. As soon as you press <space> or <enter>, after typing testattack, your Telnet session should be reset.

    Trying ... Open 
    User Access Verification 
    !--- Host has been blocked due to the 
    !--- signature "testattack" being triggered.
    [Connection to lost]
  5. Telnet to the router (House) and enter the command show access-list.

    house#show access-list 
    Extended IP access list IDS_Ethernet1_in_1 
    10 permit ip host any
    !--- You will see a temporary entry has been added to 
    !--- the access list to block the router from which you connected via Telnet previously.
    20 deny ip host any (37 matches) 
    30 permit ip any any 
  6. From the Event Viewer, click Query Database for new events now to view the alert for the previously launched attack.


  7. In the Event Viewer, highlight and right-click the alarm, then select View Context Buffer or View NSDB to view more detailed information about the alarm.

    Note: The NSDB is also available online at the Cisco Secure Encyclopedia (registered customers only) .



Troubleshooting Procedure

Use the following procedure for troubleshooting purposes.

  1. In the IDS MC, select Reports > Generate.

    Depending on the problem type, further detail should be found in one of the seven available reports.


  2. At the Sensor console, enter the command show statistics networkaccess and check the output to ensure the "state" is active.

    sensor5#show statistics networkAccess 
    Current Configuration 
       AllowSensorShun = false 
       ShunMaxEntries = 100 
          Type = Cisco 
          IP = 
          NATAddr = 
          Communications = telnet 
             InterfaceName = FastEthernet0/1 
             InterfaceDirection = in 
       ShunEnable = true 
          IP = 
          AclSupport = uses Named ACLs 
          State = Active 
             IP = 
             ShunMinutes = 15 
             MinutesRemaining = 12 
  3. Ensure the communication parameter shows that the correct protocol is being used, such as Telnet or Secure Shell (SSH) with 3DES.

    You can try a manual SSH or Telnet from an SSH/Telnet client on a PC to check username and password credentials are correct. You can then try Telnet or SSH from the Sensor itself, to the router, to ensure you are able to login successfully.

Related Information

Updated: Jun 16, 2008
Document ID: 46743