Chapter 15 Unified Threat Management for FortiOS 5.0 : Custom Application & IPS Signatures : Custom signature keywords : IP header keywords : ip_ttl
  
ip_ttl
Syntax: --ip_ttl [< | >] <ttl_int>;
Description:
Check the IP time-to-live value against the specified value. Optionally, you can check for an IP time-to-live greater-than (>) or less-than (<) the specified value with the appropriate symbol.