Traceroute command
✗ traceroute google.com
traceroute to google.com (172.217.170.206), 30 hops max, 60 byte packets
1 _gateway (172.20.52.1) 1.229 ms 2.019 ms 1.164 ms
2 197.136.187.85 (197.136.187.85) 1.147 ms 1.125 ms 1.100 ms
3 sgl.pe-moi-main-01.e.kenet.or.ke (41.204.179.49) 2.737 ms 2.990 ms 2.702 ms
4 kl.uon-moi-trunk.kenet.or.ke (41.204.173.37) 11.297 ms 9.899 ms 11.255 ms
5 kl.seacom-cls-02.s.kenet.or.ke (41.204.184.114) 18.269 ms 17.950 ms 17.936 ms
6 72.14.220.40 (72.14.220.40) 18.677 ms 17.560 ms 17.502 ms
7 192.178.251.145 (192.178.251.145) 18.041 ms 192.178.251.165 (192.178.251.165) 16.682 ms 16.387 ms
8 209.85.242.181 (209.85.242.181) 15.484 ms 16.737 ms 16.300 ms
9 mba01s10-in-f14.1e100.net (172.217.170.206) 17.983 ms 23.855 ms 17.585 ms
The output you’ve shared is from the traceroute command, which tracks the path your network traffic takes from your system to google.com. Here's a breakdown of what each part of the output means:
Hop 1: gateway (172.20.52.1) – This is your local gateway or router. It’s the first step in the network path, and the round-trip time is very low (~1 ms), as it’s within your local network.
Hop 2: 197.136.187.85 – This is likely the next router or hop in the internet backbone that handles the traffic between your network and external networks. The response time is also low (~1 ms).
Hop 3: sgl.pe-moi-main-01.e.kenet.or.ke (41.204.179.49) – This hop seems to be related to your local ISP or regional network provider. The response time is slightly higher (~2 ms).
Hop 4: kl.uon-moi-trunk.kenet.or.ke (41.204.173.37) – A further routing hop through your local provider's network.
Hop 5: kl.seacom-cls-02.s.kenet.or.ke (41.204.184.114) – Another hop through the regional network infrastructure, with a response time of around 18 ms.
Hop 6: 72.14.220.40 – This hop marks your traffic moving into a backbone provider (probably an international transit provider like Google or a partner network). The response time is still fairly low (~17 ms).
Hop 7: 192.178.251.145 and 192.178.251.165 – These are intermediate routers that handle traffic closer to Google’s network.
Hop 8: 209.85.242.181 – This hop is likely part of Google's infrastructure, still in the transit towards its data centers.
Hop 9: mba01s10-in-f14.1e100.net (172.217.170.206) – Finally, this is the Google server you're reaching. The response time is around 17 ms, which shows that the packet has reached its destination.
Summary:
The traceroute shows that your packets travel through multiple hops within your local ISP network, a regional network, and then various Google infrastructure routers before reaching the final destination (Google's servers). The round-trip times (RTTs) are quite low and stable, indicating a healthy network connection.
TRACEPATH(8) iputils TRACEPATH(8)
NAME
tracepath - traces path to a network host discovering MTU along this path
SYNOPSIS
tracepath [-4] [-6] [-n] [-b] [-l pktlen] [-m max_hops] [-p port] [-V] {destination}
DESCRIPTION
It traces the network path to destination discovering MTU along this path. It uses UDP port port or some random port. It is
similar to traceroute. However, it does not require superuser privileges and has no fancy options.
tracepath -6 is a good replacement for traceroute6 and classic example of application of Linux error queues. The situation
with IPv4 is worse, because commercial IP routers do not return enough information in ICMP error messages. Probably, it
will change, when they are updated. For now it uses Van Jacobson's trick, sweeping a range of UDP ports to maintain trace
history.
OPTIONS
-4
Use IPv4 only.
-6
Use IPv6 only.
-n
Print primarily IP addresses numerically.
-b
Print both: Host names and IP addresses.
-l
Sets the initial packet length to pktlen instead of 65535 for IPv4 or 128000 for IPv6.
-m
Set maximum hops (or maximum TTLs) to max_hops instead of 30.
-p
Sets the initial destination port to use.
-V
Print version and exit.
OUTPUT
root@mops:~ # tracepath -6 3ffe:2400:0:109::2
1?: [LOCALHOST] pmtu 1500
1: dust.inr.ac.ru 0.411ms
2: dust.inr.ac.ru asymm 1 0.390ms pmtu 1480
2: 3ffe:2400:0:109::2 463.514ms reached
Resume: pmtu 1480 hops 2 back 2
The first column shows the TTL of the probe, followed by colon. Usually the value of TTL is obtained from the reply from
the network, but sometimes it does not contain the necessary information and we have to guess it. In this case the number
is followed by ?.
The second column shows the network hop which replied to the probe. It is either the address of the router or the word
[LOCALHOST], if the probe was not sent to the network.
The rest of the line shows miscellaneous information about the path to the corresponding network hop. It contains the value
of RTT, and additionally it can show Path MTU when it changes. If the path is asymmetric or the probe finishes before it
reaches the prescribed hop, the number of hops in return direction is shown next to the keyword "asymm". This information
is not reliable, e.g. the third line shows asymmetry of 1. This is because the first probe with TTL of 2 was rejected at
the first hop due to Path MTU Discovery.
The last line summarizes information about all the paths to the destination. It shows detected Path MTU, amount of hops to
the destination and our guess about the number of hops from the destination to us, which can be different when the path is
asymmetric.
HANDLING ERRORS
In case of errors tracepath prints short error code.
┌─────────────┬──────────────┬──────────────────────────────────┐
│ Output │ Code │ Meaning │
├─────────────┼──────────────┼──────────────────────────────────┤
│ !A │ EACCES │ Communication administratively │
│ │ │ prohibited │
├─────────────┼──────────────┼──────────────────────────────────┤
│ !H │ EHOSTUNREACH │ Destination host unreachable │
├─────────────┼──────────────┼──────────────────────────────────┤
│ !N │ ENETUNREACH │ Destination network unreachable │
├─────────────┼──────────────┼──────────────────────────────────┤
│ !P │ EPROTO │ Destination protocol unreachable │
├─────────────┼──────────────┼──────────────────────────────────┤
│ pmtu N │ EMSGSIZE │ Message too long │
├─────────────┼──────────────┼──────────────────────────────────┤
│ reached │ ECONNREFUSED │ Connection refused │
├─────────────┼──────────────┼──────────────────────────────────┤
│ │ ETIMEDOUT │ Connection timed out │
├─────────────┼──────────────┼──────────────────────────────────┤
│ NET ERROR N │ │ Any other error │
└─────────────┴──────────────┴──────────────────────────────────┘
SEE ALSO
traceroute(8), traceroute6(8), ping(8).
AUTHOR
tracepath was written by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>.
SECURITY
No security issues.
This lapidary deserves to be elaborated. tracepath is not a privileged program, unlike traceroute, ping and other beasts
of their kind. tracepath may be executed by everyone who has enough access to the network to send UDP datagrams to the
desired destination using the given port.
AVAILABILITY
tracepath is part of iputils package.
iputils 20240905 TRACEPATH(8)
TRACEROUTE(8) Traceroute For Linux TRACEROUTE(8)
NAME
traceroute - print the route packets trace to network host
SYNOPSIS
traceroute [-46dFITUnreAV] [-f first_ttl] [-g gate,...]
[-i device] [-m max_ttl] [-p port] [-s src_addr]
[-q nqueries] [-N squeries] [-t tos]
[-l flow_label] [-w waittimes] [-z sendwait] [-UL] [-D]
[-P proto] [--sport=port] [-M method] [-O mod_options]
[--mtu] [--back]
host [packet_len]
traceroute6 [options]
DESCRIPTION
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 destination host . The optional packet_len‘gth is the total
size of the probing packet (default 60 bytes for IPv4 and 80 for IPv6). The specified size can be ignored in some situa‐
tions 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 certain timeout, 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 vio‐
lation), !C (precedence cutoff in effect), or !<num> (ICMP unreachable code <num>). 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 tracerouting (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 particu‐
lar 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).
OPTIONS
--help Print help info and exit.
-4, -6 Explicitly force IPv4 or IPv6 tracerouting. By default, the program will try to resolve the name given, and choose
the appropriate protocol automatically. If resolving a host name returns both IPv4 and IPv6 addresses, traceroute
will use IPv4.
-I, --icmp
Use ICMP ECHO for probes
-T, --tcp
Use TCP SYN for probes
-d, --debug
Enable socket level debugging (when the Linux kernel supports it)
-F, --dont-fragment
Do not fragment probe packets. (For IPv4 it also sets DF bit, which tells intermediate routers not to fragment re‐
motely as well).
Varying the size of the probing packet by the packet_len 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.
-f first_ttl, --first=first_ttl
Specifies with what TTL to start. Defaults to 1.
-g gateway, --gateway=gateway
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 disabled 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).
-i interface, --interface=interface
Specifies the interface through which traceroute should send packets. By default, the interface is selected accord‐
ing to the routing table.
-m max_ttl, --max-hops=max_ttl
Specifies the maximum number of hops (max time-to-live value) traceroute will probe. The default is 30.
-N squeries, --sim-queries=squeries
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.
-n Do not try to map IP addresses to host names when displaying them.
-p port, --port=port
For UDP tracing, specifies the destination port base traceroute will use (the destination port number will be incre‐
mented 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.
-t tos, --tos=tos
For IPv4, set the Type of Service (TOS) and Precedence value. Useful values are 16 (low delay) and 8 (high through‐
put). Note that in order to use some TOS precedence values, you have to be super user.
For IPv6, set the Traffic Control value.
-l flow_label, --flowlabel=flow_label
Use specified flow_label for IPv6 packets.
-w max[,here,near], --wait=max[,here,near]
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 reasonable 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 timeout 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).
-q nqueries, --queries=nqueries
Sets the number of probe packets per hop. The default is 3.
-r Bypass the normal routing tables and send directly to a host on an attached network. If the host is not on a di‐
rectly-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.
-s source_addr, --source=source_addr
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.
-z sendwait, --sendwait=sendwait
Minimal time interval between probes (default 0). If the value is more than 10, then it specifies a number in mil‐
liseconds, else it is a number of seconds (float point values allowed too). Useful when some routers use rate-limit
for ICMP messages.
-e, --extensions
Show ICMP extensions (rfc4884). The general form is CLASS/TYPE: followed by a hexadecimal dump. The MPLS (rfc4950)
is shown parsed, in a form: MPLS:L=label,E=exp_use,S=stack_bottom,T=TTL (more objects separated by / ). The Inter‐
face Information (rfc5837) is shown parsed as well, in a following form: {INC|SUB|OUT|NXT}:in‐
dex,IP_addr,"name",mtu=MTU (all four fields may be missing).
-A, --as-path-lookups
Perform AS path lookups in routing registries and print results directly after the corresponding addresses.
-V, --version
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 applicable) are chosen by the system.
--fwmark=mark
Set the firewall mark for outgoing packets (since the Linux kernel 2.6.25).
-M method, --module=name
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 shortcuts, (-I means -M icmp, etc).
-O option, --options=options
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 op‐
tions, use -O help.
-U, --udp
Use UDP to particular destination port for tracerouting (instead of increasing the port per each probe). Default
port is 53 (dns).
-UL Use UDPLITE for tracerouting (default port is 53).
-D, --dccp
Use DCCP Requests for probes.
-P protocol, --protocol=protocol
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 as‐
sumption 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' .
LIST OF AVAILABLE METHODS
In general, a particular traceroute method may have to be chosen by -M name, but most of the methods have their simple cmd‐
line switches (you can see them after the method name, if present).
default
The traditional, ancient method of tracerouting. Used by default.
Probe packets are udp datagrams with so-called "unlikely" destination ports. The "unlikely" port of the first probe is
33434, then for each next probe it is incremented by one. Since the ports are expected to be unused, the destination host
normally returns "icmp unreach port" as a final response. (Nobody knows what happens when some application listens for
such ports, though).
This method is allowed for unprivileged users.
icmp -I
Most usual method for now, which uses icmp echo packets for probes.
If you can ping(8) the destination host, icmp tracerouting is applicable as well.
This method may be allowed for unprivileged users since the kernel 3.0 (IPv4, for IPv6 since 3.11), which supports new
dgram icmp (or "ping") sockets. To allow such sockets, sysadmin should provide net/ipv4/ping_group_range sysctl range to
match any group of the user.
Options:
raw Use only raw sockets (the traditional way).
This way is tried first by default (for compatibility reasons), then new dgram icmp sockets as fallback.
dgram Use only dgram icmp sockets.
tcp -T
Well-known modern method, intended to bypass firewalls.
Uses the constant destination port (default is 80, http).
If some filters are present in the network path, then most probably any "unlikely" udp ports (as for default method) or
even icmp echoes (as for icmp) are filtered, and whole tracerouting will just stop at such a firewall. To bypass a network
filter, we have to use only allowed protocol/port combinations. If we trace for some, say, mailserver, then more likely -T
-p 25 can reach it, even when -I can not.
This method uses well-known "half-open technique", which prevents applications on the destination host from seeing our
probes at all. Normally, a tcp syn is sent. For non-listened ports we receive tcp reset, and all is done. For active lis‐
tening ports we receive tcp syn+ack, but answer by tcp reset (instead of expected tcp ack), this way the remote tcp session
is dropped even without the application ever taking notice.
There is a couple of options for tcp method:
syn,ack,fin,rst,psh,urg,ece,cwr
Sets specified tcp flags for probe packet, in any combination.
flags=num
Sets the flags field in the tcp header exactly to num.
ecn Send syn packet with tcp flags ECE and CWR (for Explicit Congestion Notification, rfc3168).
sack,timestamps,window_scaling
Use the corresponding tcp header option in the outgoing probe packet.
sysctl Use current sysctl (/proc/sys/net/*) setting for the tcp header options above and ecn. Always set by default, if
nothing else specified.
fastopen
Use fastopen tcp option (when syn), for initial cookie negotiation only.
mss=[num]
Use value of num (or unchanged) for maxseg tcp header option (when syn), and discover its clamping along the path
being traced. New changed mss is printed once in a form of M=NUM at the first probe on which it was detected.
Note, some routers may return too short original fragment in the time exceeded message, making the check impossible.
Besides that the responses may come in a different order. All this can lead to a later place of the report (using
-N 1 can help for the order).
info Print tcp flags and supported options of final tcp replies when the target host is reached. Allows to determine
whether an application listens the port and other useful things. Supported tcp options are all that can be set by
-T -O, ie. mss, sack, timestamps, window_scaling and fastopen, with the similar output format (a value for mss and
just presence for others).
Default options is syn,sysctl.
tcpconn
An initial implementation of tcp method, simple using connect(2) call, which does full tcp session opening. Not recommended
for normal use, because a destination application is always affected (and can be confused).
udp -U
Use udp datagram with constant destination port (default 53, dns).
Intended to bypass firewall as well.
Note, that unlike in tcp method, the correspond application on the destination host always receive our probes (with random
data), and most can easily be confused by them. Most cases it will not respond to our packets though, so we will never see
the final hop in the trace. (Fortunately, it seems that at least dns servers replies with something angry).
This method is allowed for unprivileged users.
udplite -UL
Use udplite datagram for probes (with constant destination port, default 53).
This method is allowed for unprivileged users.
Options:
coverage=num
Set udplite send coverage to num.
dccp -D
Use DCCP Request packets for probes (rfc4340).
This method uses the same "half-open technique" as used for TCP. The default destination port is 33434.
Options:
service=num
Set DCCP service code to num (default is 1885957735).
raw -P proto
Send raw packet of protocol proto.
No protocol-specific headers are used, just IP header only.
Implies -N 1 -w 5 .
Options:
protocol=proto
Use IP protocol proto (default 253).
NOTES
To speed up work, normally several probes are sent simultaneously. On the other hand, it creates a "storm of packages",
especially in the reply direction. Routers can throttle the rate of icmp responses, and some of replies can be lost. To
avoid this, decrease the number of simultaneous probes, or even set it to 1 (like in initial traceroute implementation),
i.e. -N 1
The final (target) host can drop some of the simultaneous probes, and might even answer only the latest ones. It can lead
to extra "looks like expired" hops near the final hop. We use a smart algorithm to auto-detect such a situation, but if it
cannot help in your case, just use -N 1 too.
For even greater stability you can slow down the program's work by -z option, for example use -z 0.5 for half-second pause
between probes.
To avoid an extra waiting, we use adaptive algorithm for timeouts (see -w option for more info). It can lead to premature
expiry (especially when response times differ at times) and printing "*" instead of a time. In such a case, switch this al‐
gorithm off, by specifying -w with the desired timeout only (for example, -w 5).
If some hops report nothing for every method, the last chance to obtain something is to use ping -R command (IPv4, and for
nearest 8 hops only).
SEE ALSO
ping(8), ping6(8), tcpdump(8), netstat(8)
Traceroute 11 October 2006 TRACEROUTE(8)