PRTRACEROUTE(8)

NAME
prtraceroute - print the route and policy information packets take to a network host.

SYNOPSIS
prtraceroute [ -m max_tll ] [ -n ] [ -n ] [ -p port ] [ -q nqueries ] [ -r ] [ -s src_addr ] [ -t tos ] [ -v ] [ -w waittime ] host [ packetsize ]

DESCRIPTION
Prtraceroute works just as the original traceroute with the addition of routing policy analysis as provided by the Internet Routing Registery (IRR). Prtraceroute will record the series of gateways traversed by packets from the originating host to the destination host, including policy analysis for each hop.

Routing in the Internet is a two level hiearchy. The highest level of routing is performed between Autonomous Systems (AS), typically using the Border Gateway Protocol (BGP). The second level of routing occurs within each AS and is administered independently by each AS. The routing policies, as registered in the IRR indicate the policies that each AS uses to communicate with all of it's peer ASs. Prtraceroute will display the route actually taken and how that route compares with the information maintained in the IRR.

prtraceroute ignores error and warning messages due to communication to the database server or parsing policy objects. Please see -ignore_errors and -report_errors options below.

IRRToolSet COMMON OPTIONS

-help
    Print summary of command-line options and abort.

-T [whois_query | whois_response | input | all]
    Trace the argument. Useful for debugging.

-D <integer>
    Print debugging messages of debug channel <integer> (if compiled with DEBUG defined).

-version
    Print the version number and quit.

-h <host-name>
    Establish a whois connection to host <host-name>. The default is whois.radb.net.

-p <port-no>
    Establish a whois connection to port <port-no>. The default is 43.

-rusage
    Print resource usage upon completion.

-ignore_errors
    Do not print error and warning messages due to communication to the database server or parsing policy objects.

-report_errors
    Print error and warning messages due to communication to the database server or parsing policy objects.

-protocol <protocol>
    Use the <protocol> to connect to the IRR server. <protocol> can be irrd(rawhoisd), ripe(bird), and ripe_perl. The default is irrd. The ripe_perl option should be used with the old ripe server.

-s <source-list>
    Consider the sources specified in the comma separated <source-list>. If an object is defined in multiple sources in <source-list>, pmatch uses the definition first encountered in <source-list> from left to right.

ENVIRONMENT VARIABLES

    IRR_HOST
        Specifies the IRR host to connect.

    IRR_PORT
        Specifies the IRR port number to connect.

    IRR_SOURCES
        Specifies the source list (comma separated) to consider.

Command line options take precedence over environment variables.

OTHER OPTIONS

    -m n
        Set the max time-to-live (max number of hops) used in outgoing probe packets. The default is 30 hops (the same default used for TCP connections).

    -n  Print hop addresses numerically rather than symbolically and numerically (saves a nameserver address-to-name lookup for each gateway found on the path).

    -p n
        Set the base UDP port number used in probes (default is 33434). Traceroute hopes that nothing is listening on UDP ports base to base+nhops-1 at the destination host (so an ICMP PORT_UNREACHABLE message will be returned to terminate the route tracing). If something is listening on a port in the default range, this option can be used to pick an unused port range.

    -r  Bypass the normal routing tables and send directly to a host on an attached network. If the host is not on a directly-attached network, an error is returned. This option can be used to ping a local host through an interface that has no route through it (e.g., after the interface was dropped by routed(8C)).

    -s addr
        Use addr as the IP address (which must be given as an IP number, not a hostname) as the source address in outgoing probe packets. On hosts with more than one IP address, this option can be used to force the source address to be something other than the IP address of the interface the probe packet is sent on. If the IP address is not one of this machine's interface addresses, an error is returned and nothing is sent.

    -s addr
        Use addr as the IP address (which must be given as an IP number, not a hostname) as the source address in outgoing probe packets. On hosts with more than one IP address, this option can be used to force the source address to be something other than the IP address of the interface the probe packet is sent on. If the IP address is not one of this machine's interface addresses, an error is returned and nothing is sent.

    -g addr
        Enable the IP LSRR (Loose Source Record Route) option in addition to the TTL tests. This is useful for asking how somebody else, at IP address addr, reaches a particular target.

    -t tos
        Set the type-of-service in probe packets to the following value (default zero). The value must be a decimal integer in the range 0 to 255. This option can be used to see if different types-of-service result in different paths. (If you are not running 4.4bsd, this may be academic since the normal network services like telnet and ftp don't let you control the TOS). Not all values of TOS are legal or meaningful - see the IP spec for definitions. Useful values are probably `-t 16' (low delay) and `-t 8' (high throughput).

    -v  Verbose output. Received ICMP packets other than TIME_EXCEEDED and UNREACHABLEs are listed.

    -w n
        Set the time to wait for a response to a probe to n seconds (default 3 sec.).

    This program attempts to trace the route an IP packet would follow to some internet host by launching UDP 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" (which means we got to "host") or hit a max (which defaults to 30 hops & can be changed with the -m flag). Three probes (change with -q flag) 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. If the probe answers come from different gateways, the address of each responding system will be printed. If there is no response within a 3 sec. timeout interval (changed with the -w flag), a "*" is printed for that probe.

    We don't want the destination host to process the UDP probe packets so the destination port is set to an unlikely value (if some clod on the destination is using that value, it can be changed with the -p flag).

    A sample use and output might be:

        [yak 71]% traceroute nis.nsf.net.
        traceroute to nis.nsf.net (35.1.1.48), 30 hops max, 56 byte packet
         1  helios.ee.lbl.gov (128.3.112.1)  19 ms  19 ms  0 ms
         2  lilac-dmc.Berkeley.EDU (128.32.216.1)  39 ms  39 ms  19 ms
         3  lilac-dmc.Berkeley.EDU (128.32.216.1)  39 ms  39 ms  19 ms
         4  ccngw-ner-cc.Berkeley.EDU (128.32.136.23)  39 ms  40 ms  39 ms
         5  ccn-nerif22.Berkeley.EDU (128.32.168.22)  39 ms  39 ms  39 ms
         6  128.32.197.4 (128.32.197.4)  40 ms  59 ms  59 ms
         7  131.119.2.5 (131.119.2.5)  59 ms  59 ms  59 ms
         8  129.140.70.13 (129.140.70.13)  99 ms  99 ms  80 ms
         9  129.140.71.6 (129.140.71.6)  139 ms  239 ms  319 ms
        10  129.140.81.7 (129.140.81.7)  220 ms  199 ms  199 ms
        11  nic.merit.edu (35.1.1.48)  239 ms  239 ms  239 ms

    Note that lines 2 & 3 are the same. This is due to a buggy kernel on the 2nd hop system - lbl-csam.arpa - that forwards packets with a zero ttl (a bug in the distributed version of 4.3BSD).

    A more interesting example is:

        [yak 72]% traceroute allspice.lcs.mit.edu.
        traceroute to allspice.lcs.mit.edu (18.26.0.115), 30 hops max
         1  helios.ee.lbl.gov (128.3.112.1)  0 ms  0 ms  0 ms
         2  lilac-dmc.Berkeley.EDU (128.32.216.1)  19 ms  19 ms  19 ms
         3  lilac-dmc.Berkeley.EDU (128.32.216.1)  39 ms  19 ms  19 ms
         4  ccngw-ner-cc.Berkeley.EDU (128.32.136.23)  19 ms  39 ms  39 ms
         5  ccn-nerif22.Berkeley.EDU (128.32.168.22)  20 ms  39 ms  39 ms
         6  128.32.197.4 (128.32.197.4)  59 ms  119 ms  39 ms
         7  131.119.2.5 (131.119.2.5)  59 ms  59 ms  39 ms
         8  129.140.70.13 (129.140.70.13)  80 ms  79 ms  99 ms
         9  129.140.71.6 (129.140.71.6)  139 ms  139 ms  159 ms
        10  129.140.81.7 (129.140.81.7)  199 ms  180 ms  300 ms
        11  129.140.72.17 (129.140.72.17)  300 ms  239 ms  239 ms
        12  * * *
        13  128.121.54.72 (128.121.54.72)  259 ms  499 ms  279 ms
        14  * * *
        15  * * *
        16  * * *
        17  * * *
        18  ALLSPICE.LCS.MIT.EDU (18.26.0.115)  339 ms  279 ms  279 ms

    Note that the gateways 12, 14, 15, 16 & 17 hops away either don't send ICMP "time exceeded" messages or send them with a ttl too small to reach us. 14 - 17 are running the MIT C Gateway code that doesn't send "time exceeded"s. God only knows what's going on with 12.

    The silent gateway 12 in the above may be the result of a bug in the 4.[23]BSD network code (and its derivatives): 4.x (x <= 3) sends an unreachable message using whatever ttl remains in the original datagram. Since, for gateways, the remaining ttl is zero, the ICMP "time exceeded" is guaranteed to not make it back to us. The behavior of this bug is slightly more interesting when it appears on the destination system:

         1  helios.ee.lbl.gov (128.3.112.1)  0 ms  0 ms  0 ms
         2  lilac-dmc.Berkeley.EDU (128.32.216.1)  39 ms  19 ms  39 ms
         3  lilac-dmc.Berkeley.EDU (128.32.216.1)  19 ms  39 ms  19 ms
         4  ccngw-ner-cc.Berkeley.EDU (128.32.136.23)  39 ms  40 ms  19 ms
         5  ccn-nerif35.Berkeley.EDU (128.32.168.35)  39 ms  39 ms  39 ms
         6  csgw.Berkeley.EDU (128.32.133.254)  39 ms  59 ms  39 ms
         7  * * *
         8  * * *
         9  * * *
        10  * * *
        11  * * *
        12  * * *
        13  rip.Berkeley.EDU (128.32.131.22)  59 ms !  39 ms !  39 ms !

    Notice that there are 12 "gateways" (13 is the final destination) and exactly the last half of them are "missing". What's really happening is that rip (a Sun-3 running Sun OS3.5) is using the ttl from our arriving datagram as the ttl in its ICMP reply. So, the reply will time out on the return path (with no notice sent to anyone since ICMP's aren't sent for ICMP's) until we probe with a ttl that's at least twice the path length. I.e., rip is really only 7 hops away. A reply that returns with a ttl of 1 is a clue this problem exists. Traceroute prints a "!" after the time if the ttl is <= 1. Since vendors ship a lot of obsolete (DEC's Ultrix, Sun 3.x) or non-standard (HPUX) software, expect to see this problem frequently and/or take care picking the target host of your probes.

    Other possible annotations after the time are !H, !N, !P (got a host, network or protocol unreachable, respectively),
    !S or !F (source route failed or fragmentation needed - neither of these should ever occur and the associated gateway is busted if you see one). If almost all the probes result in some kind of unreachable, traceroute will give up and exit.

        traceroute -g 10.3.0.5 128.182.0.0

    will show the path from the Cambridge Mailbridge to PSC while

        traceroute -g 192.5.146.4 -g 10.3.0.5 35.0.0.0

    shows how the Cambridge Mailbrige reaches Merit, by using PSC to reach the Mailbridge.

    This program is intended for use in network testing, measurement and management. It should be used primarily for manual fault isolation. Because of the load it could impose on the network, it is unwise to use traceroute during normal operations or from automated scripts.

POLICY EXAMPLE
An example run could produce the following output.
    [1335] kit.isi.edu > prtraceroute ftp.ripe.net
    prtraceroute to ftp.ripe.net (193.0.0.195), 30 hops max, 12 byte packets
     1  [AS226] cisco2-160.isi.edu (128.9.160.2)  9.531 ms  9.755 ms  8.841 ms
     2  [AS226] ln-gw32.isi.edu (128.9.32.1)  124.38 ms  15.269 ms  17.034 ms
     3  [AS226] 130.152.168.1 (130.152.168.1)  16.77 ms  10.429 ms  10.187 ms
     4  [AS2150] SWRL-ISI-GW.LN.NET (204.102.78.2)  63.025 ms  193.177 ms  17.107 ms
     5  [AS3561] border1-hssi1-0.Bloomington.mci.net (204.70.48.5)  16.474 ms  15.876 ms  15.211 ms
     6  [AS3561] core1-fddi-0.Bloomington.mci.net (204.70.2.129)  53.068 ms  215.841 ms  40.662 ms
     7  [AS3561] core1.Washington.mci.net (204.70.4.129)  79.217 ms  84.029 ms  82.851 ms
     8  [AS3561] core1-hssi-3.NewYork.mci.net (204.70.1.6)  85.65 ms  85.414 ms  84.62 ms
     9  [AS3561] 204.70.2.30 (204.70.2.30)  84.562 ms  85.313 ms  85.524 ms
    10  [AS3561] surfnet.NewYork.mci.net (204.189.136.154)  186.696 ms  194.363 ms  184.965 ms
    11  [AS1103] Amsterdam2.router.surfnet.nl (145.41.6.66)  195.545 ms  195.767 ms  187.228 ms
    12  [AS1200] Amsterdam.ripe.net (193.148.15.68)  193.955 ms  196.1 ms  182.065 ms
    13  [AS3333] info.ripe.net (193.0.0.195)  211.185 ms  265.305 ms  278.876 ms
    Path taken: AS226 AS2150 AS3561 AS1103 AS1200 AS3333
     13   AS3333 info.ripe.net                     destination -> !as-out
     12   AS1200 Amsterdam.ripe.net                     !as-in -> as-out
     11   AS1103 Amsterdam2.router.surfnet.nl           !as-in -> as-out
     10   AS3561 surfnet.NewYork.mci.net              as-in: 1 -> internal
      9   AS3561 204.70.2.30                          internal -> internal
      8   AS3561 core1-hssi-3.NewYork.mci.net         internal -> internal
      7   AS3561 core1.Washington.mci.net             internal -> internal
      6   AS3561 core1-fddi-0.Bloomington.mci.net     internal -> internal
      5   AS3561 border1-hssi1-0.Bloomington.mci.net  internal -> as-out
      4   AS2150 SWRL-ISI-GW.LN.NET                     !as-in -> !as-out
      3    AS226 130.152.168.1                          !as-in -> internal
      2    AS226 ln-gw32.isi.edu                      internal -> internal
      1    AS226 cisco2-160.isi.edu                   internal -> internal
      0    AS226 kit.isi.edu                          internal -> source
The first group of lines (1-13) are similiar to the output of traceroute with one addition, the AS number is included in square brackets, for example cisco2-160.isi.edu is in AS226. The second part of the output:
    Path taken: AS226 AS2150 AS3561 AS1103 AS1200 AS3333
simply lists the ASs traversed by this route.

The third part of the output provides the policy analysis as registered in the IRR. Notice that the output is provided in reverse order, or destination first until the source. This reflects the manner in which routes are advertised and propagated in the Internet. In other words, AS3333 announces the prefix "193.0.0.0/24" which "info.ripe.net (193.0.0.195)" belongs. AS1200, accepts the prefix and in turn announces it according to it's as-out policies and so on. As an example, the first three fields are
 10 AS3561 surfnet.NewYork.mci.net as-in: 1 -> internal The TTL, AS and Gateway fields are the same as we have seen. The 'as-in: 1 - internal' part of the above output describes the routing policy registered in the IRR. The first field 'as-in: 1' is the import field and the 'internal' is the export field. In this example, 'as-in: 1' in the import field means that the prefix was accepted via an as-in policy and the 1 indicates that it was the highest preference (a 2 would indicate the second most prefered, etc.) The export field contains 'internal', meaning the next hop is in the same AS as the current hop. Following is a list of possible values that can be present in the import field:

Destination
    Current hop is the destination host.

Internal
    The current hop and next hop (TTL+1) belong to the same AS.

as-in: 1
    The prefix announcement from the next hop AS (TTL+1) was the first preferred hop from the current AS to the destination prefix. A value of 2 would indicate that the next hop was the second preferred route according to the current hop, and so on.

default: 1
    TTL+1 was the first preferred default route. A value of 2 would indicate that the next hop was the second prefeered default, etc.

!as-in
    The current AS has no registered as-in or default policy to accept prefixes being exported from the next hop (TTL+1).

The following list describes the possible values that can be provided in the export field of the analysis portion of the output.

Source
    This host is the source of the execution

Internel
    The current hop is the same AS as previous hop (TTL-1).

as-out
    This indicates that the current AS announces the prefix to the previous AS.

!as-out
    This indicates that the current AS has no policy to announce the prefix to the previous hop.

From our example above,
     13   AS3333 info.ripe.net                       destination - !as-out
     12   AS1200 Amsterdam.ripe.net                      !as-in - as-out
     11   AS1103 Amsterdam2.router.surfnet.nl            !as-in - as-out
     10   AS3561 surfnet.NewYork.mci.net               as-in: 1 - internal
      9   AS3561 204.70.2.30                           internal - internal

we can conclude: That info.ripe.net was the destination host and is part of AS3333. AS3333 provides no as-out policy announcing prefix 193.0.0.0/24 to AS1200 and AS1200 provides no as-in policy accepting prefix 193.0.0.0/24 from AS3333. This flags a two way policy inconsistency between AS3333 and AS1200. AS1200 announces to AS1103 and AS1103 has no policy to accept the prefix from AS1200. This indicates incomplete policy information for AS1103 on behalf of AS1200. AS1103 announces to AS3561 and that AS3561 uses AS1103 as it's most preferred route for the prefix in question. This is the only policy that is complete by both ASs in this example. Finally the hop between surfnet.NewYork.mci.net and 204.70.2.30 is internel since both gateways belong to AS361.

AUTHOR
The original traceroute was implemented by Van Jacobson from a suggestion by Steve Deering. Debugged by a cast of thousands with particularly cogent suggestions or fixes from C. Philip Wood, Tim Seaver and Ken Adelman. The code was then mangled into C++ and the Routing Policy support was added for this version of prtraceroute.

SEE ALSO
netstat(1), ping(8), prpath(1) peval(1)