{ "content": [ { "type": "text", "text": "# traceroute-nanog (man)\n\n## NAME\n\ntraceroute - print the route packets trace to network host\n\n## SYNOPSIS\n\ntraceroute [-46dFITUnreAV] [-f firstttl] [-g gate,...]\n[-i device] [-m maxttl] [-p port] [-s srcaddr]\n[-q nqueries] [-N squeries] [-t tos]\n[-l flowlabel] [-w waittimes] [-z sendwait] [-UL] [-D]\n[-P proto] [--sport=port] [-M method] [-O modoptions]\n[--mtu] [--back]\nhost [packetlen]\ntraceroute6 [options]\ntcptraceroute [options]\nlft [options]\n\n## DESCRIPTION\n\ntraceroute tracks the route packets taken from an IP network on their way to a given host. It\nutilizes the IP protocol's time to live (TTL) field and attempts to elicit an ICMP TIMEEX‐\nCEEDED response from each gateway along the path to the host.\n\n## Sections\n\n- **NAME**\n- **SYNOPSIS**\n- **DESCRIPTION**\n- **OPTIONS** (28 subsections)\n- **LIST OF AVAILABLE METHODS** (12 subsections)\n- **NOTES** (3 subsections)\n- **SEE ALSO**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n" } ], "structuredContent": { "command": "traceroute-nanog", "section": "", "mode": "man", "summary": "traceroute - print the route packets trace to network host", "synopsis": "traceroute [-46dFITUnreAV] [-f firstttl] [-g gate,...]\n[-i device] [-m maxttl] [-p port] [-s srcaddr]\n[-q nqueries] [-N squeries] [-t tos]\n[-l flowlabel] [-w waittimes] [-z sendwait] [-UL] [-D]\n[-P proto] [--sport=port] [-M method] [-O modoptions]\n[--mtu] [--back]\nhost [packetlen]\ntraceroute6 [options]\ntcptraceroute [options]\nlft [options]", "tldr_summary": null, "tldr_examples": [], "tldr_source": null, "flags": [ { "flag": "-6", "long": null, "arg": null, "description": "solve the name given, and choose the appropriate protocol automatically. If resolving a host name returns both IPv4 and IPv6 addresses, traceroute will use IPv4." }, { "flag": "-I", "long": "--icmp", "arg": null, "description": "Use ICMP ECHO for probes" }, { "flag": "-T", "long": "--tcp", "arg": null, "description": "Use TCP SYN for probes" }, { "flag": "-d", "long": "--debug", "arg": null, "description": "Enable socket level debugging (when the Linux kernel supports it)" }, { "flag": "-F", "long": "--dont-fragment", "arg": null, "description": "Do not fragment probe packets. (For IPv4 it also sets DF bit, which tells intermediate routers not to fragment remotely as well). Varying the size of the probing packet by the packetlen command line parameter, you can manually obtain information about the MTU of individual network hops. The --mtu option (see below) tries to do this automatically. Note, that non-fragmented features (like -F or --mtu) work properly since the Linux kernel 2.6.22 only. Before that version, IPv6 was always fragmented, IPv4 could use the once the discovered final mtu only (from the route cache), which can be less than the actual mtu of a device." }, { "flag": "-f", "long": null, "arg": null, "description": "Specifies with what TTL to start. Defaults to 1." }, { "flag": "-g", "long": null, "arg": null, "description": "Tells traceroute to add an IP source routing option to the outgoing packet that tells the network to route the packet through the specified gateway (most routers have dis‐ abled source routing for security reasons). In general, several gateway's is allowed (comma separated). For IPv6, the form of num,addr,addr... is allowed, where num is a route header type (default is type 2). Note the type 0 route header is now deprecated (rfc5095)." }, { "flag": "-i", "long": null, "arg": null, "description": "Specifies the interface through which traceroute should send packets. By default, the interface is selected according to the routing table." }, { "flag": "-m", "long": null, "arg": null, "description": "Specifies the maximum number of hops (max time-to-live value) traceroute will probe. The default is 30." }, { "flag": "-N", "long": null, "arg": null, "description": "Specifies the number of probe packets sent out simultaneously. Sending several probes concurrently can speed up traceroute considerably. The default value is 16. Note that some routers and hosts can use ICMP rate throttling. In such a situation specifying too large number can lead to loss of some responses." }, { "flag": "-n", "long": null, "arg": null, "description": "" }, { "flag": "-p", "long": null, "arg": null, "description": "For UDP tracing, specifies the destination port base traceroute will use (the destina‐ tion port number will be incremented by each probe). For ICMP tracing, specifies the initial ICMP sequence value (incremented by each probe too). For TCP and others specifies just the (constant) destination port to connect. When us‐ ing the tcptraceroute wrapper, -p specifies the source port." }, { "flag": "-t", "long": null, "arg": null, "description": "For IPv4, set the Type of Service (TOS) and Precedence value. Useful values are 16 (low delay) and 8 (high throughput). Note that in order to use some TOS precedence values, you have to be super user. For IPv6, set the Traffic Control value." }, { "flag": "-l", "long": null, "arg": null, "description": "Use specified flowlabel for IPv6 packets." }, { "flag": "-w", "long": null, "arg": null, "description": "Determines how long to wait for a response to a probe. There are three (in general) float values separated by a comma (or a slash). Max specifies the maximum time (in seconds, default 5.0) to wait, in any case. Traditional traceroute implementation always waited whole max seconds for any probe. But if we already have some replies from the same hop, or even from some next hop, we can use the round trip time of such a reply as a hint to determine the actual reason‐ able amount of time to wait. The optional here (default 3.0) specifies a factor to multiply the round trip time of an already received response from the same hop. The resulting value is used as a time‐ out for the probe, instead of (but no more than) max. The optional near (default 10.0) specifies a similar factor for a response from some next hop. (The time of the first found result is used in both cases). First, we look for the same hop (of the probe which will be printed first from now). If nothing found, then look for some next hop. If nothing found, use max. If here and/or near have zero values, the corresponding computation is skipped. Here and near are always set to zero if only max is specified (for compatibility with previous versions)." }, { "flag": "-q", "long": null, "arg": null, "description": "Sets the number of probe packets per hop. The default is 3." }, { "flag": "-r", "long": null, "arg": null, "description": "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." }, { "flag": "-s", "long": null, "arg": null, "description": "Chooses an alternative source address. Note that you must select the address of one of the interfaces. By default, the address of the outgoing interface is used." }, { "flag": "-z", "long": null, "arg": null, "description": "Minimal time interval between probes (default 0). If the value is more than 10, then it specifies a number in milliseconds, else it is a number of seconds (float point values allowed too). Useful when some routers use rate-limit for ICMP messages." }, { "flag": "-e", "long": "--extensions", "arg": null, "description": "Show ICMP extensions (rfc4884). The general form is CLASS/TYPE: followed by a hexadec‐ imal dump. The MPLS (rfc4950) is shown parsed, in a form: MPLS:L=la‐ bel,E=expuse,S=stackbottom,T=TTL (more objects separated by / ). The Interface In‐ formation (rfc5837) is shown parsed as well, in a following form: {INC|SUB|OUT|NXT}:index,IPaddr,\"name\",mtu=MTU (all four fields may be missing)." }, { "flag": "-A", "long": "--as-path-lookups", "arg": null, "description": "Perform AS path lookups in routing registries and print results directly after the corresponding addresses." }, { "flag": "-V", "long": "--version", "arg": null, "description": "Print the version and exit. There are additional options intended for advanced usage (such as alternate trace methods etc.): --sport=port Chooses the source port to use. Implies -N 1 -w 5 . Normally source ports (if applic‐ able) are chosen by the system. --fwmark=mark Set the firewall mark for outgoing packets (since the Linux kernel 2.6.25)." }, { "flag": "-M", "long": null, "arg": null, "description": "Use specified method for traceroute operations. Default traditional udp method has name default, icmp (-I) and tcp (-T) have names icmp and tcp respectively. Method-specific options can be passed by -O . Most methods have their simple short‐ cuts, (-I means -M icmp, etc)." }, { "flag": "-O", "long": null, "arg": null, "description": "Specifies some method-specific option. Several options are separated by comma (or use several -O on cmdline). Each method may have its own specific options, or many not have them at all. To print information about available options, use -O help." }, { "flag": "-U", "long": "--udp", "arg": null, "description": "Use UDP to particular destination port for tracerouting (instead of increasing the port per each probe). Default port is 53 (dns)." }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "-D", "long": "--dccp", "arg": null, "description": "Use DCCP Requests for probes." }, { "flag": "-P", "long": null, "arg": null, "description": "Use raw packet of specified protocol for tracerouting. Default protocol is 253 (rfc3692). --mtu Discover MTU along the path being traced. Implies -F -N 1. New mtu is printed once in a form of F=NUM at the first probe of a hop which requires such mtu to be reached. (Actually, the correspond \"frag needed\" icmp message normally is sent by the previous hop). Note, that some routers might cache once the seen information on a fragmentation. Thus you can receive the final mtu from a closer hop. Try to specify an unusual tos by -t , this can help for one attempt (then it can be cached there as well). See -F option for more info. --back Print the number of backward hops when it seems different with the forward direction. This number is guessed in assumption that remote hops send reply packets with initial ttl set to either 64, or 128 or 255 (which seems a common practice). It is printed as a negate value in a form of '-NUM' ." } ], "examples": [], "see_also": [ { "name": "ping", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/ping/8/json" }, { "name": "ping6", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/ping6/8/json" }, { "name": "tcpdump", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/tcpdump/8/json" }, { "name": "netstat", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/netstat/8/json" } ], "section_outline": [ { "name": "NAME", "lines": 2, "subsections": [] }, { "name": "SYNOPSIS", "lines": 11, "subsections": [] }, { "name": "DESCRIPTION", "lines": 45, "subsections": [] }, { "name": "OPTIONS", "lines": 2, "subsections": [ { "name": "-4 -6", "lines": 3, "flag": "-6" }, { "name": "-I, --icmp", "lines": 2, "flag": "-I", "long": "--icmp" }, { "name": "-T, --tcp", "lines": 2, "flag": "-T", "long": "--tcp" }, { "name": "-d, --debug", "lines": 2, "flag": "-d", "long": "--debug" }, { "name": "-F, --dont-fragment", "lines": 12, "flag": "-F", "long": "--dont-fragment" }, { "name": "-f _", "lines": 2, "flag": "-f" }, { "name": "-g _", "lines": 7, "flag": "-g" }, { "name": "-i _", "lines": 3, "flag": "-i" }, { "name": "-m _", "lines": 3, "flag": "-m" }, { "name": "-N _", "lines": 5, "flag": "-N" }, { "name": "-n", "lines": 1, "flag": "-n" }, { "name": "-p _", "lines": 7, "flag": "-p" }, { "name": "-t _", "lines": 5, "flag": "-t" }, { "name": "-l _", "lines": 2, "flag": "-l" }, { "name": "-w _", "lines": 22, "flag": "-w" }, { "name": "-q _", "lines": 2, "flag": "-q" }, { "name": "-r", "lines": 3, "flag": "-r" }, { "name": "-s _", "lines": 3, "flag": "-s" }, { "name": "-z _", "lines": 4, "flag": "-z" }, { "name": "-e, --extensions", "lines": 6, "flag": "-e", "long": "--extensions" }, { "name": "-A, --as-path-lookups", "lines": 3, "flag": "-A", "long": "--as-path-lookups" }, { "name": "-V, --version", "lines": 12, "flag": "-V", "long": "--version" }, { "name": "-M _", "lines": 5, "flag": "-M" }, { "name": "-O _", "lines": 4, "flag": "-O" }, { "name": "-U, --udp", "lines": 3, "flag": "-U", "long": "--udp" }, { "name": "-UL", "lines": 1 }, { "name": "-D, --dccp", "lines": 2, "flag": "-D", "long": "--dccp" }, { "name": "-P _", "lines": 18, "flag": "-P" } ] }, { "name": "LIST OF AVAILABLE METHODS", "lines": 4, "subsections": [ { "name": "default", "lines": 10 }, { "name": "icmp -I", "lines": 14 }, { "name": "tcp -T", "lines": 7 }, { "name": "-p 25 -I", "lines": 8, "flag": "-I" }, { "name": "syn,ack,fin,rst,psh,urg,ece,cwr", "lines": 8 }, { "name": "sack,timestamps,window_scaling", "lines": 5 }, { "name": "fastopen", "lines": 18 }, { "name": "tcpconn", "lines": 4 }, { "name": "udp -U", "lines": 10 }, { "name": "udplite -UL", "lines": 8 }, { "name": "dccp -D", "lines": 10 }, { "name": "raw -P proto", "lines": 8 } ] }, { "name": "NOTES", "lines": 4, "subsections": [ { "name": "-N 1", "lines": 3, "flag": "-N" }, { "name": "-N 1", "lines": 1, "flag": "-N" }, { "name": "-z 0.5", "lines": 8, "flag": "-z" } ] }, { "name": "SEE ALSO", "lines": 3, "subsections": [] } ], "sections": { "NAME": { "content": "traceroute - print the route packets trace to network host\n", "subsections": [] }, "SYNOPSIS": { "content": "traceroute [-46dFITUnreAV] [-f firstttl] [-g gate,...]\n[-i device] [-m maxttl] [-p port] [-s srcaddr]\n[-q nqueries] [-N squeries] [-t tos]\n[-l flowlabel] [-w waittimes] [-z sendwait] [-UL] [-D]\n[-P proto] [--sport=port] [-M method] [-O modoptions]\n[--mtu] [--back]\nhost [packetlen]\ntraceroute6 [options]\ntcptraceroute [options]\nlft [options]\n", "subsections": [] }, "DESCRIPTION": { "content": "traceroute tracks the route packets taken from an IP network on their way to a given host. It\nutilizes the IP protocol's time to live (TTL) field and attempts to elicit an ICMP TIMEEX‐\nCEEDED response from each gateway along the path to the host.\n\ntraceroute6 is equivalent to traceroute -6\n\ntcptraceroute is equivalent to traceroute -T\n\nlft , the Layer Four Traceroute, performs a TCP traceroute, like traceroute -T , but attempts\nto provide compatibility with the original such implementation, also called \"lft\".\n\nThe only required parameter is the name or IP address of the destination host . The optional\npacketlen`gth is the total size of the probing packet (default 60 bytes for IPv4 and 80 for\nIPv6). The specified size can be ignored in some situations or increased up to a minimal\nvalue.\n\nThis program attempts to trace the route an IP packet would follow to some internet host by\nlaunching probe packets with a small ttl (time to live) then listening for an ICMP \"time ex‐\nceeded\" reply from a gateway. We start our probes with a ttl of one and increase by one un‐\ntil we get an ICMP \"port unreachable\" (or TCP reset), which means we got to the \"host\", or\nhit a max (which defaults to 30 hops). Three probes (by default) are sent at each ttl setting\nand a line is printed showing the ttl, address of the gateway and round trip time of each\nprobe. The address can be followed by additional information when requested. If the probe an‐\nswers come from different gateways, the address of each responding system will be printed.\nIf there is no response within a certain timeout, an \"*\" (asterisk) is printed for that\nprobe.\n\nAfter the trip time, some additional annotation can be printed: !H, !N, or !P (host, network\nor protocol unreachable), !S (source route failed), !F (fragmentation needed), !X (communica‐\ntion administratively prohibited), !V (host precedence violation), !C (precedence cutoff in\neffect), or ! (ICMP unreachable code ). If almost all the probes result in some\nkind of unreachable, traceroute will give up and exit.\n\nWe don't want the destination host to process the UDP probe packets, so the destination port\nis set to an unlikely value (you can change it with the -p flag). There is no such a problem\nfor ICMP or TCP tracerouting (for TCP we use half-open technique, which prevents our probes\nto be seen by applications on the destination host).\n\nIn the modern network environment the traditional traceroute methods can not be always ap‐\nplicable, because of widespread use of firewalls. Such firewalls filter the \"unlikely\" UDP\nports, or even ICMP echoes. To solve this, some additional tracerouting methods are imple‐\nmented (including tcp), see LIST OF AVAILABLE METHODS below. Such methods try to use particu‐\nlar protocol and source/destination port, in order to bypass firewalls (to be seen by fire‐\nwalls just as a start of allowed type of a network session).\n", "subsections": [] }, "OPTIONS": { "content": "--help Print help info and exit.\n", "subsections": [ { "name": "-4 -6", "content": "solve the name given, and choose the appropriate protocol automatically. If resolving\na host name returns both IPv4 and IPv6 addresses, traceroute will use IPv4.\n", "flag": "-6" }, { "name": "-I, --icmp", "content": "Use ICMP ECHO for probes\n", "flag": "-I", "long": "--icmp" }, { "name": "-T, --tcp", "content": "Use TCP SYN for probes\n", "flag": "-T", "long": "--tcp" }, { "name": "-d, --debug", "content": "Enable socket level debugging (when the Linux kernel supports it)\n", "flag": "-d", "long": "--debug" }, { "name": "-F, --dont-fragment", "content": "Do not fragment probe packets. (For IPv4 it also sets DF bit, which tells intermediate\nrouters not to fragment remotely as well).\n\nVarying the size of the probing packet by the packetlen command line parameter, you\ncan manually obtain information about the MTU of individual network hops. The --mtu\noption (see below) tries to do this automatically.\n\nNote, that non-fragmented features (like -F or --mtu) work properly since the Linux\nkernel 2.6.22 only. Before that version, IPv6 was always fragmented, IPv4 could use\nthe once the discovered final mtu only (from the route cache), which can be less than\nthe actual mtu of a device.\n", "flag": "-F", "long": "--dont-fragment" }, { "name": "-f _", "content": "Specifies with what TTL to start. Defaults to 1.\n", "flag": "-f" }, { "name": "-g _", "content": "Tells traceroute to add an IP source routing option to the outgoing packet that tells\nthe network to route the packet through the specified gateway (most routers have dis‐\nabled source routing for security reasons). In general, several gateway's is allowed\n(comma separated). For IPv6, the form of num,addr,addr... is allowed, where num is a\nroute header type (default is type 2). Note the type 0 route header is now deprecated\n(rfc5095).\n", "flag": "-g" }, { "name": "-i _", "content": "Specifies the interface through which traceroute should send packets. By default, the\ninterface is selected according to the routing table.\n", "flag": "-i" }, { "name": "-m _", "content": "Specifies the maximum number of hops (max time-to-live value) traceroute will probe.\nThe default is 30.\n", "flag": "-m" }, { "name": "-N _", "content": "Specifies the number of probe packets sent out simultaneously. Sending several probes\nconcurrently can speed up traceroute considerably. The default value is 16.\nNote that some routers and hosts can use ICMP rate throttling. In such a situation\nspecifying too large number can lead to loss of some responses.\n", "flag": "-N" }, { "name": "-n", "content": "", "flag": "-n" }, { "name": "-p _", "content": "For UDP tracing, specifies the destination port base traceroute will use (the destina‐\ntion port number will be incremented by each probe).\nFor ICMP tracing, specifies the initial ICMP sequence value (incremented by each probe\ntoo).\nFor TCP and others specifies just the (constant) destination port to connect. When us‐\ning the tcptraceroute wrapper, -p specifies the source port.\n", "flag": "-p" }, { "name": "-t _", "content": "For IPv4, set the Type of Service (TOS) and Precedence value. Useful values are 16\n(low delay) and 8 (high throughput). Note that in order to use some TOS precedence\nvalues, you have to be super user.\nFor IPv6, set the Traffic Control value.\n", "flag": "-t" }, { "name": "-l _", "content": "Use specified flowlabel for IPv6 packets.\n", "flag": "-l" }, { "name": "-w _", "content": "Determines how long to wait for a response to a probe.\n\nThere are three (in general) float values separated by a comma (or a slash). Max\nspecifies the maximum time (in seconds, default 5.0) to wait, in any case.\n\nTraditional traceroute implementation always waited whole max seconds for any probe.\nBut if we already have some replies from the same hop, or even from some next hop, we\ncan use the round trip time of such a reply as a hint to determine the actual reason‐\nable amount of time to wait.\n\nThe optional here (default 3.0) specifies a factor to multiply the round trip time of\nan already received response from the same hop. The resulting value is used as a time‐\nout for the probe, instead of (but no more than) max. The optional near (default\n10.0) specifies a similar factor for a response from some next hop. (The time of the\nfirst found result is used in both cases).\n\nFirst, we look for the same hop (of the probe which will be printed first from now).\nIf nothing found, then look for some next hop. If nothing found, use max. If here\nand/or near have zero values, the corresponding computation is skipped.\nHere and near are always set to zero if only max is specified (for compatibility with\nprevious versions).\n", "flag": "-w" }, { "name": "-q _", "content": "Sets the number of probe packets per hop. The default is 3.\n", "flag": "-q" }, { "name": "-r", "content": "If the host is not on a directly-attached network, an error is returned. This option\ncan be used to ping a local host through an interface that has no route through it.\n", "flag": "-r" }, { "name": "-s _", "content": "Chooses an alternative source address. Note that you must select the address of one of\nthe interfaces. By default, the address of the outgoing interface is used.\n", "flag": "-s" }, { "name": "-z _", "content": "Minimal time interval between probes (default 0). If the value is more than 10, then\nit specifies a number in milliseconds, else it is a number of seconds (float point\nvalues allowed too). Useful when some routers use rate-limit for ICMP messages.\n", "flag": "-z" }, { "name": "-e, --extensions", "content": "Show ICMP extensions (rfc4884). The general form is CLASS/TYPE: followed by a hexadec‐\nimal dump. The MPLS (rfc4950) is shown parsed, in a form: MPLS:L=la‐\nbel,E=expuse,S=stackbottom,T=TTL (more objects separated by / ). The Interface In‐\nformation (rfc5837) is shown parsed as well, in a following form:\n{INC|SUB|OUT|NXT}:index,IPaddr,\"name\",mtu=MTU (all four fields may be missing).\n", "flag": "-e", "long": "--extensions" }, { "name": "-A, --as-path-lookups", "content": "Perform AS path lookups in routing registries and print results directly after the\ncorresponding addresses.\n", "flag": "-A", "long": "--as-path-lookups" }, { "name": "-V, --version", "content": "Print the version and exit.\n\nThere are additional options intended for advanced usage (such as alternate trace methods\netc.):\n\n--sport=port\nChooses the source port to use. Implies -N 1 -w 5 . Normally source ports (if applic‐\nable) are chosen by the system.\n\n--fwmark=mark\nSet the firewall mark for outgoing packets (since the Linux kernel 2.6.25).\n", "flag": "-V", "long": "--version" }, { "name": "-M _", "content": "Use specified method for traceroute operations. Default traditional udp method has\nname default, icmp (-I) and tcp (-T) have names icmp and tcp respectively.\nMethod-specific options can be passed by -O . Most methods have their simple short‐\ncuts, (-I means -M icmp, etc).\n", "flag": "-M" }, { "name": "-O _", "content": "Specifies some method-specific option. Several options are separated by comma (or use\nseveral -O on cmdline). Each method may have its own specific options, or many not\nhave them at all. To print information about available options, use -O help.\n", "flag": "-O" }, { "name": "-U, --udp", "content": "Use UDP to particular destination port for tracerouting (instead of increasing the\nport per each probe). Default port is 53 (dns).\n", "flag": "-U", "long": "--udp" }, { "name": "-UL", "content": "" }, { "name": "-D, --dccp", "content": "Use DCCP Requests for probes.\n", "flag": "-D", "long": "--dccp" }, { "name": "-P _", "content": "Use raw packet of specified protocol for tracerouting. Default protocol is 253\n(rfc3692).\n\n--mtu Discover MTU along the path being traced. Implies -F -N 1. New mtu is printed once in\na form of F=NUM at the first probe of a hop which requires such mtu to be reached.\n(Actually, the correspond \"frag needed\" icmp message normally is sent by the previous\nhop).\n\nNote, that some routers might cache once the seen information on a fragmentation. Thus\nyou can receive the final mtu from a closer hop. Try to specify an unusual tos by -t\n, this can help for one attempt (then it can be cached there as well).\nSee -F option for more info.\n\n--back Print the number of backward hops when it seems different with the forward direction.\nThis number is guessed in assumption that remote hops send reply packets with initial\nttl set to either 64, or 128 or 255 (which seems a common practice). It is printed as\na negate value in a form of '-NUM' .\n", "flag": "-P" } ] }, "LIST OF AVAILABLE METHODS": { "content": "In general, a particular traceroute method may have to be chosen by -M name, but most of the\nmethods have their simple cmdline switches (you can see them after the method name, if\npresent).\n", "subsections": [ { "name": "default", "content": "The traditional, ancient method of tracerouting. Used by default.\n\nProbe packets are udp datagrams with so-called \"unlikely\" destination ports. The \"unlikely\"\nport of the first probe is 33434, then for each next probe it is incremented by one. Since\nthe ports are expected to be unused, the destination host normally returns \"icmp unreach\nport\" as a final response. (Nobody knows what happens when some application listens for such\nports, though).\n\nThis method is allowed for unprivileged users.\n" }, { "name": "icmp -I", "content": "Most usual method for now, which uses icmp echo packets for probes.\nIf you can ping(8) the destination host, icmp tracerouting is applicable as well.\n\nThis method may be allowed for unprivileged users since the kernel 3.0 (IPv4, for IPv6 since\n3.11), which supports new dgram icmp (or \"ping\") sockets. To allow such sockets, sysadmin\nshould provide net/ipv4/pinggrouprange sysctl range to match any group of the user.\nOptions:\n\nraw Use only raw sockets (the traditional way).\nThis way is tried first by default (for compatibility reasons), then new dgram icmp\nsockets as fallback.\n\ndgram Use only dgram icmp sockets.\n" }, { "name": "tcp -T", "content": "Well-known modern method, intended to bypass firewalls.\nUses the constant destination port (default is 80, http).\n\nIf some filters are present in the network path, then most probably any \"unlikely\" udp ports\n(as for default method) or even icmp echoes (as for icmp) are filtered, and whole tracerout‐\ning will just stop at such a firewall. To bypass a network filter, we have to use only al‐\nlowed protocol/port combinations. If we trace for some, say, mailserver, then more likely -T" }, { "name": "-p 25 -I", "content": "This method uses well-known \"half-open technique\", which prevents applications on the desti‐\nnation host from seeing our probes at all. Normally, a tcp syn is sent. For non-listened\nports we receive tcp reset, and all is done. For active listening ports we receive tcp\nsyn+ack, but answer by tcp reset (instead of expected tcp ack), this way the remote tcp ses‐\nsion is dropped even without the application ever taking notice.\n\nThere is a couple of options for tcp method:\n", "flag": "-I" }, { "name": "syn,ack,fin,rst,psh,urg,ece,cwr", "content": "Sets specified tcp flags for probe packet, in any combination.\n\nflags=num\nSets the flags field in the tcp header exactly to num.\n\necn Send syn packet with tcp flags ECE and CWR (for Explicit Congestion Notification,\nrfc3168).\n" }, { "name": "sack,timestamps,window_scaling", "content": "Use the corresponding tcp header option in the outgoing probe packet.\n\nsysctl Use current sysctl (/proc/sys/net/*) setting for the tcp header options above and ecn.\nAlways set by default, if nothing else specified.\n" }, { "name": "fastopen", "content": "Use fastopen tcp option (when syn), for initial cookie negotiation only.\n\nmss=[num]\nUse value of num (or unchanged) for maxseg tcp header option (when syn), and discover\nits clamping along the path being traced. New changed mss is printed once in a form\nof M=NUM at the first probe on which it was detected. Note, some routers may return\ntoo short original fragment in the time exceeded message, making the check impossible.\nBesides that the responses may come in a different order. All this can lead to a\nlater place of the report (using -N 1 can help for the order).\n\ninfo Print tcp flags and supported options of final tcp replies when the target host is\nreached. Allows to determine whether an application listens the port and other useful\nthings. Supported tcp options are all that can be set by -T -O, ie. mss, sack, time‐\nstamps, windowscaling and fastopen, with the similar output format (a value for mss\nand just presence for others).\n\nDefault options is syn,sysctl.\n" }, { "name": "tcpconn", "content": "An initial implementation of tcp method, simple using connect(2) call, which does full tcp\nsession opening. Not recommended for normal use, because a destination application is always\naffected (and can be confused).\n" }, { "name": "udp -U", "content": "Use udp datagram with constant destination port (default 53, dns).\nIntended to bypass firewall as well.\n\nNote, that unlike in tcp method, the correspond application on the destination host always\nreceive our probes (with random data), and most can easily be confused by them. Most cases it\nwill not respond to our packets though, so we will never see the final hop in the trace.\n(Fortunately, it seems that at least dns servers replies with something angry).\n\nThis method is allowed for unprivileged users.\n" }, { "name": "udplite -UL", "content": "Use udplite datagram for probes (with constant destination port, default 53).\n\nThis method is allowed for unprivileged users.\nOptions:\n\ncoverage=num\nSet udplite send coverage to num.\n" }, { "name": "dccp -D", "content": "Use DCCP Request packets for probes (rfc4340).\n\nThis method uses the same \"half-open technique\" as used for TCP. The default destination\nport is 33434.\n\nOptions:\n\nservice=num\nSet DCCP service code to num (default is 1885957735).\n" }, { "name": "raw -P proto", "content": "Send raw packet of protocol proto.\nNo protocol-specific headers are used, just IP header only.\nImplies -N 1 -w 5 .\nOptions:\n\nprotocol=proto\nUse IP protocol proto (default 253).\n" } ] }, "NOTES": { "content": "To speed up work, normally several probes are sent simultaneously. On the other hand, it\ncreates a \"storm of packages\", especially in the reply direction. Routers can throttle the\nrate of icmp responses, and some of replies can be lost. To avoid this, decrease the number\nof simultaneous probes, or even set it to 1 (like in initial traceroute implementation), i.e.", "subsections": [ { "name": "-N 1", "content": "The final (target) host can drop some of the simultaneous probes, and might even answer only\nthe latest ones. It can lead to extra \"looks like expired\" hops near the final hop. We use a\nsmart algorithm to auto-detect such a situation, but if it cannot help in your case, just use", "flag": "-N" }, { "name": "-N 1", "content": "For even greater stability you can slow down the program's work by -z option, for example use", "flag": "-N" }, { "name": "-z 0.5", "content": "To avoid an extra waiting, we use adaptive algorithm for timeouts (see -w option for more\ninfo). It can lead to premature expiry (especially when response times differ at times) and\nprinting \"*\" instead of a time. In such a case, switch this algorithm off, by specifying -w\nwith the desired timeout only (for example, -w 5).\n\nIf some hops report nothing for every method, the last chance to obtain something is to use\nping -R command (IPv4, and for nearest 8 hops only).\n", "flag": "-z" } ] }, "SEE ALSO": { "content": "ping(8), ping6(8), tcpdump(8), netstat(8)\n\nTraceroute 11 October 2006 TRACEROUTE(1)", "subsections": [] } } } }