In the course of typical network administration, it is common to attempt to ping the Cisco Secure Access Control Server (ACS) Solution Engine in order to determine if the appliance is up and reachable. However, these pings fail due to enhanced security restrictions in place on the appliance.
There are no specific requirements for this document.
The information in this document is based on the Cisco Secure ACS Solution Engine.
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.
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The Cisco Secure ACS Solution Engine, also known as the Cisco Secure ACS Appliance, is based on Microsoft Windows, and therefore is vulnerable to PMTUD attacks and to attacks based on ICMP "hard" error messages. Such attacks are detailed in the Crafted ICMP Messages Can Cause Denial of Service security advisory.
Recent versions of the Cisco Secure ACS Solution Engine ship with Cisco Security Agent (CSA), which is configured to block all incoming ICMP messages. Under this situation, the Cisco Secure ACS Solution Engine is not vulnerable to any of the attacks that this document describes.
The Cisco Secure ACS Solution Engine does not respond to pings like a normal, Windows-based Cisco Secure ACS server.
The failure of the Cisco Secure ACS Solution Engine to respond to pings is the result of the rule set applied to the CSA installed on the appliance.
In order to allow ping on your ACS Solution Engine, you need to disable the CSA. This can be done via the System Configuration > Appliance Configuration menu. There is an option to disable or enable the CSA. If you disable this agent, you can then ping the appliance.
Note: Disable CSA only if you want to verify the pings to work.
Instead of monitoring the status of the appliance with the use of ICMP, you can verify it is up and reachable when you connect to the appliance on TCP port 2002. Telnet to the appliance on port 2002 and press Enter. You should see the error: HTTP 500 Internal Server Error
This is an example of this procedure performed at the Windows command line:
C:\>telnet 172.18.124.101 2002 <enter> <enter> HTTP/1.0 500 Internal Server Error Connection to host lost. C:\>
Additionally, you can download several free TCP ping-type utilities from the Internet that attempt to connect to a host on any TCP port and report back if the host responds.
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