Which action is performed first on the Cisco ASA appliance when it receives an incoming packet on its outside interface?
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A. B. C. D. E. F.C.
When an incoming packet is received on the outside interface of a Cisco ASA appliance, the first action that is performed depends on the security policy configuration and inspection rules that are configured on the device.
Here are the possible actions that may be taken:
A. Check if the packet is permitted or denied by the inbound ACL applied to the outside interface.
If an inbound ACL is configured on the outside interface of the Cisco ASA, the appliance will first check if the packet is permitted or denied by this ACL. The inbound ACL is processed before any other ACLs on the device. If the packet is denied by the inbound ACL, it will be dropped and no further processing will take place.
B. Check if the packet is permitted or denied by the global ACL.
If there is no inbound ACL on the outside interface or the packet is permitted by the inbound ACL, the Cisco ASA will check if the packet is permitted or denied by the global ACL. The global ACL is applied to all traffic that enters the device and is processed after the interface-specific ACLs.
C. Check if the packet matches an existing connection in the connection table.
If the packet is permitted by the inbound and global ACLs, the appliance will check if the packet matches an existing connection in the connection table. The Cisco ASA maintains a stateful inspection table that keeps track of all connections that pass through the device. If the packet matches an existing connection in the table, it will be allowed to pass through the device.
D. Check if the packet matches an inspection policy.
If the packet does not match an existing connection in the connection table or if there is no connection table entry for the traffic, the Cisco ASA will check if the packet matches an inspection policy. Inspection policies are used to perform application-layer inspections on the traffic, such as deep packet inspection (DPI) for HTTP, FTP, and other protocols.
E. Check if the packet matches a NAT rule.
If the packet does not match an inspection policy, the appliance will check if the packet matches a NAT rule. NAT rules are used to translate the source or destination IP address of the traffic as it passes through the device.
F. Check if the packet needs to be passed to the Cisco ASA AIP-SSM for inspections.
Finally, if the packet has not been dropped or allowed by any of the previous checks, the Cisco ASA will determine if the packet needs to be passed to the Cisco ASA AIP-SSM (Advanced Inspection and Prevention Security Services Module) for further inspection. The AIP-SSM is an optional module that provides additional security features such as intrusion prevention system (IPS) and malware detection.
In summary, the order of operations for incoming packets on the outside interface of a Cisco ASA appliance is: