Predefined NAT Limitations - Cisco CCIE Service Provider Written Exam | Cisco

Limitations of Predefined NAT


Which are the two limitations of the predefined NAT solution? (Choose two.)



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A. B. C. D. E.



The predefined NAT solution is a form of Network Address Translation (NAT) that is offered by Cisco IOS routers to enable the translation of IP addresses and/or port numbers between the private network (inside) and the public network (outside). While this solution offers some benefits such as simplicity and ease of configuration, it also has some limitations, two of which are described below:

B. It cannot be configured for each of the inside VRF instance: A Virtual Routing and Forwarding (VRF) instance is a method of isolating the routing tables of multiple routing domains on a single physical device. In the case of the predefined NAT solution, it is not possible to configure NAT for each VRF instance separately, which means that all VRFs on the router will use the same NAT settings. This limitation can be problematic in situations where different VRFs require different NAT configurations.

C. The global port limit parameter is not available for the predefined mode: In the predefined NAT solution, the router automatically assigns port numbers to NAT translations, and there is no option to specify a global port limit parameter. This means that if there are many concurrent NAT translations, there is a risk of running out of available port numbers, which could cause connections to fail.

A, D, and E are not correct answers:

A. Only the port-presentation option is available: This statement is incorrect. The predefined NAT solution supports both port-presentation and address-presentation options.

D. The Bulk Port Allocation configuration is not available: This statement is incorrect. The Bulk Port Allocation configuration is available in the predefined NAT solution.

E. NetFlow and syslog are not supported: This statement is incorrect. NetFlow and syslog are supported in the predefined NAT solution.