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block-allocation (Source NAT Next Gen Services)


Hierarchy Level


Allocate a block of ports for each subscriber to use for source NAT with port translation, except for deterministic NAT. New requests for NAT ports for the subscriber are served from the active block. With port block allocation, we generate one syslog log per set of ports allocated for a subscriber. This reduces the number of logs, making it easier to track subscribers.


active-block-timeout timeout-interval

The interval, in seconds, for which the block is active. After the timeout, a new block is allocated, even if ports are available in the active block. If you set the timeout to 0, port blocks are filled completely before a new port block is allocated, and the last port block remains active indefinitely.

  • Range: 0 through 86,400

  • Default: 0

block-size block-size

Number of ports in a block.

  • Range: 1 through 64,512

  • Default: 128

interim-logging-interval timeout-interval

The interval, in seconds, at which to send interim system logs for active port blocks and for inactive port blocks with live sessions. This increases the reliability of system logs, which are UDP-based and can get lost in the network.

  • Range: 1800 through 86,400

  • Default: 0 (interim logs are disabled)

maximum-blocks-per-host maximum-block-number

The maximum number of blocks that can be allocated to a subscriber address.

  • Range: 1 through 512

  • Default: 8

log disable

Disable logs for port block allocation. Logs are enbled by default.

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 19.3R2.