Cisco ASA 5506-X Configuration Manual page 253

Chapter 10 Inspection for Management Application Protocols
XDMCP Inspection
If you are editing an existing service policy (such as the default global policy called global_policy), you
Step 6
are done. Otherwise, activate the policy map on one or more interfaces.
service-policy policymap_name {global | interface interface_name}
Example:
hostname(config)# service-policy global_policy global
The global keyword applies the policy map to all interfaces, and interface applies the policy to one
interface. Only one global policy is allowed. You can override the global policy on an interface by
applying a service policy to that interface. You can only apply one policy map to each interface.
XDMCP Inspection
XDMCP inspection is enabled by default; however, the XDMCP inspection engine is dependent upon
proper configuration of the established command.
XDMCP is a protocol that uses UDP port 177 to negotiate X sessions, which use TCP when established.
For successful negotiation and start of an XWindows session, the ASA must allow the TCP back
connection from the Xhosted computer. To permit the back connection, use the established command
on the ASA. Once XDMCP negotiates the port to send the display, The established command is
consulted to verify if this back connection should be permitted.
During the XWindows session, the manager talks to the display Xserver on the well-known port 6000 |
n. Each display has a separate connection to the Xserver, as a result of the following terminal setting.
setenv DISPLAY Xserver:n
where n is the display number.
When XDMCP is used, the display is negotiated using IP addresses, which the ASA can NAT if needed.
XDCMP inspection does not support PAT.
For information on enabling XDMCP inspection, see Configure Application Layer Protocol Inspection,
page 6-9.
Cisco ASA Series Firewall CLI Configuration Guide
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