External Logging
External logging configures the export and logging of the NAT table entries, private bindings that are associated
with a particular global IP port address, and to use Netflow to export the NAT table entries.
Netflow v9 Support
The NAT44 and DS Lite features support Netflow for logging of the translation records. Logging of the
translation records can be mandated by for Lawful Intercept. The Netflow uses binary format and hence
requires software to parse and present the translation records.
Syslog Support
The NAT44, Stateful NAT64, and DS Lite features support Netflow for logging of the translation records.
Logging of the translation records can be mandated by for Lawful Intercept. The Netflow uses binary format
and hence requires software to parse and present the translation records.
In Cisco IOS XR Software Release 4.2.1 and later, the DS Lite and NAT44 features support Syslog as an
alternative to Netflow. Syslog uses ASCII format and hence can be read by users. However, the log data
volume is higher in Syslog than Netflow.
Bulk Port Allocation
The creation and deletion of NAT sessions need to be logged and these create huge amount of data. These
are stored on Syslog collector which is supported over UDP. In order to reduce the volume of data generated
by the NAT device, bulk port allocation can be enabled. When bulk port allocation is enabled and when a
subscriber creates the first session, a number of contiguous outside ports are pre-allocated. A bulk allocation
message is logged indicating this allocation. Subsequent session creations will use one of the pre-allocated
port and hence does not require logging.
Session-logging and bulk port allocation are mutually exclusive.Note
Destination-Based Logging
Destination-Based Logging (DBL) includes destination IPv4 address and port number in the Netflow create
and delete records used by NAT44, Stateful NAT64, and DS-Lite applications. It is also known as
Session-Logging.
Session-Logging and Bulk Port Allocation are mutually exclusive.Note
Cisco IOS XR Carrier Grade NAT Configuration Guide for the Cisco CRS Router, Release 5.2.x
OL-32659-01 21
Implementing Carrier Grade NAT on Cisco IOS XR Software
External Logging
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