Aqui está uma citação relevante da ping
manpage:
TTL DETAILS The TTL value of an IP packet represents the maximum number of IP routers that the packet can go through before being thrown away. In current practice you can expect each router in the Internet to decrement the TTL field by exactly one.
The TCP/IP specification recommends setting the TTL field for IP packets to 64, but many systems use smaller values (4.3BSD uses 30, 4.2BSD used 15).
E para citar RFC 1700:
The current recommended default time to live (TTL) for the Internet Protocol (IP) is 64.