Net::Traceroute6 - traceroute(1)/traceroute6(1) functionality in perl


    use Socket6;
    use Net::Traceroute6;
    $tr = Net::Traceroute6->new(host=> "");
    if($tr->found) {
        my $hops = $tr->hops;
        if($hops > 1) {
            print "Router was " .
                $tr->hop_query_host($tr->hops - 1, 0) . "\n";


This module implements traceroute(1)/traceroute6(1) functionality for perl5. It allows you to trace the path IP packets take to a destination. It is currently implemented as a parser around the system traceroute command.


A new Net::Traceroute6 object must be created with the new method. Depending on exactly how the constructor is invoked, it may perform the traceroute immediately, or it may return a "template" object that can be used to set parameters for several subsequent traceroutes.

Methods are available for accessing information about a given traceroute attempt. There are also methods that view/modify the options that are passed to the object's constructor.

To trace a route, UDP packets are sent with a small TTL (time-to-live) field in an attempt to get intervening routers to generate ICMP TIME_EXCEEDED messages.


    $obj = Net::Traceroute6->new([base_port     => $base_port,]
                                [debug          => $debuglvl,]
                                [max_ttl        => $max_ttl,]
                                [host           => $host,]
                                [queries        => $queries,]
                                [query_timeout  => $query_timeout,]
                                [af             => $address_family,]
                                [timeout        => $timeout,]);
    $frob = $obj->new([options]);

This is the constructor for a new Net::Traceroute6 object. If given host, it will actually perform the traceroute; otherwise it will return an empty template object. This can be used to setup a template object with some preset defaults for firing off multiple traceroutes.

Given an existing Net::Traceroute object $obj as a template, you can call $obj->new() with the usual parameters. The same rules apply about defining host; that is, traceroute will be run if it is defined. You can always pass host => undef in the constructor call.

To use a template objects to perform a traceroute, you invoke new on it and pass a host option.

Possible options are:

host - A host to traceroute to. If you don't set this, you get a Traceroute object with no traceroute data in it. The module always uses IP addresses internally and will attempt to lookup host names via inet_aton.

base_port - Base port number to use for the UDP queries. Traceroute assumes that nothing is listening to port base_port to base_port + (nhops - 1) where nhops is the number of hops required to reach the destination address. Default is what the system traceroute uses (normally 33434). Traceroute's -p option.

debuglvl - A number indicating how verbose debug information should be. Please include debug=>9 output in bug reports.

max_ttl - Maximum number of hops to try before giving up. Default is what the system traceroute uses (normally 30). Traceroute's -m option.

queries - Number of times to send a query for a given hop. Defaults to whatever the system traceroute uses (3 for most traceroutes). Traceroute's -q option.

query_timeout - How many seconds to wait for a response to each query sent. Uses the system traceroute's default value of 5 if unspecified. Traceroute's -w option.

timeout - Maximum time, in seconds, to wait for the traceroute to complete. If not specified, the traceroute will not return until the host has been reached, or traceroute counts to infinity (max_ttl * queries * query_timeout). Note that this option is implemented by Net::Traceroute, not the underlying traceroute command.

address_family - Which address family to use. Currently supported address families: PF_UNSPEC, PF_INET, PF_INET6 (if IPv6 is supported). If PF_UNSPEC used the host is specifying the currently used address family. If host has both A and AAAA addresses, then you can select the desired address family. The default is PF_UNSPEC. The Net::Traceroute6 automatically select the right traceroute tool.


Controlling traceroute invocation

Each of these methods return the current value of the option specified by the corresponding constructor option. They will set the object's instance variable to the given value if one is provided.

Changing an instance variable will only affect newly performed traceroutes. Setting a different value on a traceroute object that has already performed a trace has no effect.

See the constructor documentation for information about each method/constructor option.


Obtaining information about a Trace

These methods return information about a traceroute that has already been performed.

Any of the methods in this section that return a count of something or want an Nth type count to identify something employ one based counting.


Returns the status of a given traceroute object. One of TRACEROUTE_OK, TRACEROUTE_TIMEOUT, or TRACEROUTE_UNKNOWN (each defined as an integer). TRACEROUTE_OK will only be returned if the host was actually reachable.


Returns 1 if the host was found, undef otherwise.


Returns the number of hops that it took to reach the host.


Returns the number of queries that were sent for a given hop. This should normally be the same for every query.

hop_query_stat(HOP, QUERY)

Return the status of the given HOP's QUERY. The return status can be one of the following (each of these is actually an integer constant function defined in Net::Traceroute's export list):


Reached the host, no problems.


This query timed out.


Your guess is as good as mine. Shouldn't happen too often.


This hop returned an ICMP Network Unreachable.


This hop returned an ICMP Host Unreachable.


This hop returned an ICMP Protocol unreachable.


Indicates that you can't reach this host without fragmenting your packet further. Shouldn't happen in regular use.


A source routed packet was rejected for some reason. Shouldn't happen.


A firewall or similar device has decreed that your traffic is disallowed by administrative action. Suspect sheer, raving paranoia.


The destination machine appears to exhibit the 4.[23]BSD time exceeded bug.

hop_query_host(HOP, QUERY)

Return the dotted quad IP address of the host that responded to HOP's QUERY.

hop_query_time(HOP, QUERY)

Return the round trip time associated with the given HOP's query. If your system's traceroute supports fractional second timing, so will Net::Traceroute.

In the previous methods, you can get the first successfull QUERY parameters, if you specify QUERY number as 0.


Net::Traceroute parses the output of the system traceroute command. As such, it may not work on your system. Support for more traceroute outputs (e.g. Windows, HPUX) could be done, although currently the code assumes there is "One true traceroute".

For IPv6 currently only on some system is known to work:

*BSD (FreeBSD 4.0 or later, NetBSD 1.5 or later. OpenBSD 2.8 and later) + any KAME patched BSD

Solaris 8 or later

Currently only few ICMPv6 error options are recognised.

The actual functionality of traceroute could also be implemented natively in perl or linked in from a C library.


traceroute(1) traceroute6(1)


Janos Mohacsi <> Daniel Hagerty <>


Copyright 1998, 1999 Massachusetts Institute of Technology Copyright 2001 Janos Mohacsi