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no-decrement-ttl

 

Syntax

Hierarchy Level

Release Information

Statement introduced before Junos OS Release 7.4.

Statement introduced in Junos OS Release 12.3X50 on the QFX Series.

Statement introduced in Junos OS Evolved Release 19.3R1 on PTX10003.

Statement introduced in Junos OS Evolved Release 20.1R1 on PTX10008.

Description

Disable normal time-to-live (TTL) decrementing, which decrements the TTL field in the IP header by 1. This statement decrements the IP TTL by 1 before encapsulating the IP packet within an MPLS packet. When the penultimate router pops off the top label, it does not use the standard write-back procedure of writing the MPLS TTL into the IP TTL field. Therefore, the IP packet is decremented by 1. The ultimate router then decrements the packet by one more for a total cloud appearance of 2, thus hiding the network topology.

Default

Normal TTL decrementing enabled; the TTL field value is decremented by 1 as the packet passes through each label-switched router in the LSP.

Required Privilege Level

routing—To view this statement in the configuration.

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