Category

Linux Command


Usage

traceroute6 [options]


Manual

traceroute tracks the route packets taken from an IP network on their
way to a given host. It utilizes the IP protocol’s time to live (TTL)
field and attempts to elicit an ICMP TIME_EXCEEDED response from each
gateway along the path to the host.

traceroute6 is equivalent to traceroute -6

The only required parameter is the name or IP address of the destina-
tion host . The optional packet_len‘gth is the total size of the prob-
ing packet (default 60 bytes for IPv4 and 80 for IPv6). The specified
size can be ignored in some situations or increased up to a minimal
value.

This program attempts to trace the route an IP packet would follow to
some internet host by launching probe packets with a small ttl (time to
live) then listening for an ICMP "time exceeded" reply from a gateway.
We start our probes with a ttl of one and increase by one until we get
an ICMP "port unreachable" (or TCP reset), which means we got to the
"host", or hit a max (which defaults to 30 hops). Three probes (by
default) are sent at each ttl setting and a line is printed showing the
ttl, address of the gateway and round trip time of each probe. The
address can be followed by additional information when requested. If
the probe answers come from different gateways, the address of each
responding system will be printed. If there is no response within a
5.0 seconds (default), an "*" (asterisk) is printed for that probe.

After the trip time, some additional annotation can be printed: !H, !N,
or !P (host, network or protocol unreachable), !S (source route
failed), !F (fragmentation needed), !X (communication administratively
prohibited), !V (host precedence violation), !C (precedence cutoff in
effect), or ! (ICMP unreachable code ). If almost all the
probes result in some kind of unreachable, traceroute will give up and
exit.

We don’t want the destination host to process the UDP probe packets, so
the destination port is set to an unlikely value (you can change it
with the -p flag). There is no such a problem for ICMP or TCP tracer-
outing (for TCP we use half-open technique, which prevents our probes
to be seen by applications on the destination host).

In the modern network environment the traditional traceroute methods
can not be always applicable, because of widespread use of firewalls.
Such firewalls filter the "unlikely" UDP ports, or even ICMP echoes.
To solve this, some additional tracerouting methods are implemented
(including tcp), see LIST OF AVAILABLE METHODS below. Such methods try
to use particular protocol and source/destination port, in order to
bypass firewalls (to be seen by firewalls just as a start of allowed
type of a network session).


Share your experience or ask a question