Solaris Network Troubleshooting
Solaris: Network Troubleshooting
Extracted from http://www.skywayradio.com/tech/sun/troubleshooting.html
Overview
One of the first signs of trouble on the network is a loss of communications by one or more <A href="http://XXX/sun/commands/hosts.html">hosts</A>. If a <A href="http://XXX/sun/config.html#hosts">host</A> refuses to come up at all the first time it is added to the network, the problem might lie in one of the configuration files, or in the <A href="http://www.skywayradio.com/tech/network/network_interface.html">network interface</A>. If a single host suddenly develops a problem, the <A href="http://www.skywayradio.com/tech/network/network_interface.html">network interface</A> might be the cause. If the <A href="http://XXX/sun/commands/hosts.html">hosts</A> on a network can communicate with each other but not with other <A href="http://XXX/pages/commands/networks.html">networks</A>, the problem could lie with the <A href="http://XXX/sun/planning.html#routers">router</A>, or it could lie in another network.
You can use the <A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A> program to obtain information on <A href="http://www.skywayradio.com/tech/network/network_interface.html">network interfaces</A> and <A href="http://XXX/sun/commands/netstat.html">netstat</A> to display routing tables and protocol statistics. Third-party network diagnostic programs provide a number of troubleshooting utilities. Refer to third-party documentation for information.
Less obvious are the causes of problems that degrade performance on the network. For example, you can use tools like <A href="http://XXX/pages/commands/ping.html">ping</A> to quantify problems like the loss of packets by a <A href="http://XXX/sun/config.html#hosts">host</A>.
<A class name="software"></A>==Running Software Checks==
If the network has trouble, some actions that you can take to diagnose and fix software-related problems include:
*Using the <A href="http://XXX/sun/commands/netstat.html">netstat</A> command to display network information.
*Checking the <A href="http://XXX/sun/commands/hosts.html">hosts</A> database (and ipnodes if you are using <A href="http://www.skywayradio.com/tech/ebooks/networking/dns/ch10_14.htm">IPv6</A>) to make sure that the entries are correct and up to <A href="http://XXX/sun/commands/date.html">date</A>.
*If you are running RARP, checking the Ethernet addresses in the <A href="http://XXX/pages/commands/ethers.html">ethers</A> database to make sure that the entries are correct and up to <A href="http://XXX/sun/commands/date.html">date</A>.
*Trying to connect by <A href="http://XXX/pages/commands/telnet.html">telnet</A> to the local <A href="http://XXX/sun/config.html#hosts">host</A>.
*Ensuring that the network daemon <A href="http://XXX/pages/commands/inetd.html">inetd</A> is running. To do this, <A href="http://XXX/sun/commands/log.html">log</A> in as superuser and type:
- <A href="http://XXX/sun/commands/ps.html">ps</A> -ef | <A href="http://XXX/pages/commands/grep.html">grep</A> <A href="http://XXX/pages/commands/inetd.html">inetd</A>
Here is an example of output displayed if the <A href="http://XXX/pages/commands/inetd.html">inetd</A> daemon is running:
root 57 1 0 Apr 04 ? 3:19 /usr/sbin/inetd -s root 4218 4198 0 17:57:23 pts/3 0:00 <A href="http://XXX/pages/commands/grep.html">grep</A> <A href="http://XXX/pages/commands/inetd.html">inetd</A>
<A class name="ping"></A>==ping Command==
Use the <A href="http://XXX/pages/commands/ping.html">ping</A> command to <A href="http://XXX/sun/commands/find.html">find</A> out whether there is IP connectivity to a particular <A href="http://XXX/sun/config.html#hosts">host</A>. The basic syntax is:
/usr/sbin/ping <A href="http://XXX/sun/config.html#hosts">host</A> [timeout]
where <A href="http://XXX/sun/config.html#hosts">host</A> is the host name of the machine in question. The optional timeout argument indicates the time in seconds for <A href="http://XXX/pages/commands/ping.html">ping</A> to keep trying to reach the machine-20 seconds by default. The <A href="http://XXX/pages/commands/ping.html">ping</A>(1M) <A href="http://XXX/sun/commands/man.html">man</A> <A href="http://XXX/sun/commands/page.html">page</A> describes additional syntaxes and options.
When you run <A href="http://XXX/pages/commands/ping.html">ping</A>, the <A href="http://en.wikipedia.org/wiki/ICMP">ICMP</A> protocol sends a datagram to the <A href="http://XXX/sun/config.html#hosts">host</A> you specify, asking for a response. (<A href="http://en.wikipedia.org/wiki/ICMP">ICMP</A> is the protocol responsible for error handling on a TCP/IP network. See ICMP Protocol for details.)
How to Determine if a Host Is Running
On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command.
% <A href="http://XXX/pages/commands/ping.html">ping</A> <A href="http://XXX/pages/commands/hostname.html">hostname</A>
If <A href="http://XXX/sun/config.html#hosts">host</A> <A href="http://XXX/pages/commands/hostname.html">hostname</A> is up, this message is displayed:
hostname is alive
This indicates that <A href="http://XXX/pages/commands/hostname.html">hostname</A> responded to the <A href="http://en.wikipedia.org/wiki/ICMP">ICMP</A> request. However, if <A href="http://XXX/pages/commands/hostname.html">hostname</A> is down or cannot receive the ICMP packets, you receive the following response from <A href="http://XXX/pages/commands/ping.html">ping</A>:
no answer from <A href="http://XXX/pages/commands/hostname.html">hostname</A>
How to Determine if a Host Is Losing Packets
If you suspect that a machine might be losing packets even though it is running, you can use the s option of <A href="http://XXX/pages/commands/ping.html">ping</A> to try to detect the problem. On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command.
% <A href="http://XXX/pages/commands/ping.html">ping</A> -s <A href="http://XXX/pages/commands/hostname.html">hostname</A>
<A href="http://XXX/pages/commands/ping.html">ping</A> continually sends packets to <A href="http://XXX/pages/commands/hostname.html">hostname</A> until you send an interrupt character or a timeout occurs. The responses on your screen will resemble:
PING elvis: 56 data bytes<BR></BR>64 bytes from 129.144.50.21: icmp_seq=0. time=80. ms<BR></BR>64 bytes from 129.144.50.21: icmp_seq=1. time=0. ms<BR></BR>64 bytes from 129.144.50.21: icmp_seq=2. time=0. ms<BR></BR>64 bytes from 129.144.50.21: icmp_seq=3. time=0. ms<BR></BR>.<BR></BR>.<BR></BR>.<BR></BR>----elvis PING Statistics----<BR></BR>4 packets transmitted, 4 packets received, 0% packet loss<BR></BR>round-trip (ms) min/avg/max = 0/20/80 <BR></BR>
The packet-loss statistic indicates whether the <A href="http://XXX/sun/config.html#hosts">host</A> has dropped packets.
If <A href="http://XXX/pages/commands/ping.html">ping</A> fails, check the status of the network reported by <A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A> and <A href="http://XXX/sun/commands/netstat.html">netstat</A>, as described in ifconfig Command and <A href="http://XXX/sun/commands/netstat.html">netstat</A> Command
<A class name="ifconfig"></A>==ifconfig Command==
The <A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A> command displays information about the configuration of an interface that you specify. (Refer to the <A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A>(1M) <A href="http://XXX/sun/commands/man.html">man</A> <A href="http://XXX/sun/commands/page.html">page</A> for details.) The syntax of ifconfig is:
<A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A> interface-name [protocol_family]
How to Get Information About a Specific Interface
*Become superuser.
*On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command.
- <A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A> interface
For an le0 interface, your output resembles the following:
le0: flags=863<UP> mtu 1500<BR></BR> <A href="http://XXX/sun/commands/inet.html">inet</A> 129.144.44.140 <A href="http://XXX/sun/config.html#netmasks">netmask</A> ffffff00 broadcast 129.144.44.255<BR></BR>ether 8:0:20:8:el:fd<BR></BR></UP>
The flags section just given shows that the interface is configured "up," capable of broadcasting, and not using "trailer" <A href="http://XXX/pages/commands/link.html">link</A> level encapsulation. The mtu field tells you that this interface has a maximum transfer size of 1500 octets. Information on the second <A href="http://XXX/sun/commands/line.html">line</A> includes the IP address of the <A href="http://XXX/sun/config.html#hosts">host</A> you are using, the <A href="http://XXX/sun/config.html#netmasks">netmask</A> being currently used, and the IP broadcast address of the interface. The third line gives the machine address (Ethernet, in this case) of the <A href="http://XXX/sun/config.html#hosts">host</A>.
How to Get Information About All Interfaces on a Network
A useful <A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A> option is -a, which provides information on all interfaces on your network.
*Become superuser.
*On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command.
- <A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A> -a interface
This produces, for example:
le0: flags=49<UP> mtu 8232<BR></BR> <A href="http://XXX/sun/commands/inet.html">inet</A> 127.144.44.140 <A href="http://XXX/sun/config.html#netmasks">netmask</A> ff000000 <BR></BR>le0:flags=863<UP> mtu 1500<BR></BR> <A href="http://XXX/sun/commands/inet.html">inet</A> 129.144.44.140 <A href="http://XXX/sun/config.html#netmasks">netmask</A> ffffff00 broadcast 129.144.44.255<BR></BR>ether 8:0:20:8:el:fd<BR></BR><BR></BR></UP></UP>
Output that indicates an interface is not running might mean a problem with that interface. In this case, see the <A href="http://XXX/pages/commands/ifconfig.html">ifconfig</A>(1M) <A href="http://XXX/sun/commands/man.html">man</A> <A href="http://XXX/sun/commands/page.html">page</A>.
<A class name="netstat"></A>==netstat Command==
The <A href="http://XXX/sun/commands/netstat.html">netstat</A> command generates displays that show network status and protocol statistics. You can display the status of <A href="http://XXX/network/index.html#TCP">TCP</A> and <A href="http://XXX/network/index.html#UDP">UDP</A> endpoints in table format, routing table information, and interface information.
<A href="http://XXX/sun/commands/netstat.html">netstat</A> displays various types of network data depending on the command <A href="http://XXX/sun/commands/line.html">line</A> option selected. These displays are the most useful for system administration. The syntax for this form is:
<A href="http://XXX/sun/commands/netstat.html">netstat</A> [-m] [-n] [-s] [-i | -r] [-f address_family]
The most frequently used options for determining network status are: s, r, and i. See the <A href="http://XXX/sun/commands/netstat.html">netstat</A>(1M) <A href="http://XXX/sun/commands/man.html">man</A> <A href="http://XXX/sun/commands/page.html">page</A> for a description of the options.
How to Display Statistics by Protocol
The <A href="http://XXX/sun/commands/netstat.html">netstat</A> -s option displays per protocol statistics for the <A href="http://XXX/network/index.html#UDP">UDP</A>, <A href="http://XXX/network/index.html#TCP">TCP</A>, <A href="http://en.wikipedia.org/wiki/ICMP">ICMP</A>, and IP <A href="http://XXX/pages/commands/protocols.html">protocols</A>.
On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command.
% <A href="http://XXX/sun/commands/netstat.html">netstat</A> -s
The result resembles the display shown in the example below. (Parts of the output have been truncated.) The information can indicate areas where a protocol is having problems. For example, statistical information from <A href="http://en.wikipedia.org/wiki/ICMP">ICMP</A> can indicate where this protocol has found errors.
<A href="http://XXX/network/index.html#UDP">UDP</A><BR></BR> udpInDatagrams = 39228 udpOutDatagrams = 2455 <BR></BR> udpInErrors = 0<BR></BR> <A href="http://XXX/network/index.html#TCP">TCP</A><BR></BR><BR></BR> tcpRtoAlgorithm = 4 tcpMaxConn = -1<BR></BR> tcpRtoMax = 60000 tcpPassiveOpens = 2<BR></BR> tcpActiveOpens = 4 tcpEstabResets = 1<BR></BR> tcpAttemptFails = 3 tcpOutSegs = 315<BR></BR> .<BR></BR> .<BR></BR>IP<BR></BR> ipForwarding = 2 ipDefaultTTL = 255<BR></BR> ipInReceives = 4518 ipInHdrErrors = 0<BR></BR> .<BR></BR> . <BR></BR><A href="http://en.wikipedia.org/wiki/ICMP">ICMP</A><BR></BR> icmpInMsgs = 0 icmpInErrors = 0<BR></BR> icmpInCksumErrs = 0 icmpInUnknowns = 0<BR></BR> .<BR></BR> . <BR></BR> <A href="http://XXX/docu/multicast.html#IGMP">IGMP</A>:<BR></BR> 0 messages received<BR></BR>0 messages received with too few bytes<BR></BR>0 messages received with bad checksum<BR></BR>0 membership queries received<BR></BR>0 membership queries received with invalid field(s)<BR></BR>0 membership reports received<BR></BR>0 membership reports received with invalid field(s)<BR></BR>0 membership reports received for <A href="http://XXX/pages/commands/groups.html">groups</A> to which we belong<BR></BR>0 membership reports sent<BR></BR>
How to Display Network Interface Status
The i option of <A href="http://XXX/sun/commands/netstat.html">netstat</A> shows the state of the <A href="http://www.skywayradio.com/tech/network/network_interface.html">network interfaces</A> that are configured with the machine where you ran the command. On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command:
% <A href="http://XXX/sun/commands/netstat.html">netstat</A> -i
Here is a sample display produced by <A href="http://XXX/sun/commands/netstat.html">netstat</A> -i:
Name Mtu Net/Dest Address Ipkts Ierrs Opkts Oerrs Collis Queue<BR></BR>le0 1500 b5-spd-2f-cm tatra 14093893 8492 10174659 1119 2314178 0<BR></BR>lo0 8232 loopback localhost 92997622 5442 12451748 0 775125 0<BR></BR>
Using this display, you can <A href="http://XXX/sun/commands/find.html">find</A> out how many packets a machine thinks it has transmitted and received on each network. For example, the input packet count (Ipkts) displayed for a server can increase each time a client tries to <A href="http://XXX/pages/commands/boot.html">boot</A>, while the output packet count (Opkts) remains steady. This suggests that the server is seeing the <A href="http://XXX/pages/commands/boot.html">boot</A> request packets from the client, but does not realize it is supposed to respond to them. This might be caused by an incorrect address in the <A href="http://XXX/sun/commands/hosts.html">hosts</A>, ipnodes, or <A href="http://XXX/pages/commands/ethers.html">ethers</A> database.
On the other hand, if the input packet count is steady over time, it means that the machine does not see the packets at all. This suggests a different type of failure, possibly a hardware problem.
How to Display Routing Table Status
The -r option of <A href="http://XXX/sun/commands/netstat.html">netstat</A> displays the IP routing table. On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command.
% <A href="http://XXX/sun/commands/netstat.html">netstat</A> -r
Here is a sample display produced by <A href="http://XXX/sun/commands/netstat.html">netstat</A> -r run on machine tenere:
Routing tables<BR></BR>Destination Gateway Flags Refcnt Use Interface<BR></BR>temp8milptp elvis UGH 0 0 <BR></BR>irmcpeb1-ptp0 elvis UGH 0 0 <BR></BR>route93-ptp0 speed UGH 0 0 <BR></BR>mtvb9-ptp0 speed UGH 0 0 <BR></BR> .<BR></BR>mtnside speed UG 1 567 <BR></BR>ray-net speed UG 0 0 <BR></BR>mtnside-eng speed UG 0 36 <BR></BR>mtnside-eng speed UG 0 558 <BR></BR>mtnside-eng tenere U 33 190248 le0<BR></BR>
The first column shows the destination network, the second the <A href="http://XXX/sun/planning.html#routers">router</A> through which packets are forwarded. The U flag indicates that the <A href="http://XXX/sun/commands/route.html">route</A> is up; the G flag indicates that the route is to a <A href="http://XXX/pages/commands/gateway.html">gateway</A>. The H flag indicates that the destination is a fully qualified <A href="http://XXX/sun/config.html#hosts">host</A> address, rather than a network.
The Refcnt column shows the number of active uses per <A href="http://XXX/sun/commands/route.html">route</A>, and the Use column shows the number of packets sent per <A href="http://XXX/sun/commands/route.html">route</A>. Finally, the Interface column shows the <A href="http://www.skywayradio.com/tech/network/network_interface.html">network interface</A> that the <A href="http://XXX/sun/commands/route.html">route</A> uses.
<A class name="log"></A>==How to Log Network Problems==
*Become superuser.
*Create a <A href="http://XXX/sun/commands/log.html">log</A> file of routing daemon actions by typing the following command at a command <A href="http://XXX/sun/commands/line.html">line</A> prompt.
- /usr/sbin/in.routed /var/logfilename
Caution: On a busy network, this can generate almost continuous output.
<A class name="packet"></A>==Displaying Packet Contents==
You can use <A href="http://XXX/sun/commands/snoop.html">snoop</A> to capture network packets and display their contents. Packets can be displayed as soon as they are received, or saved to a file. When snoop writes to an intermediate file, packet loss under busy trace conditions is unlikely. snoop itself is then used to interpret the file. For information about using the snoop command, <A href="http://XXX/sun/commands/refer.html">refer</A> to the <A href="http://XXX/sun/commands/snoop.html">snoop</A>(1M) <A href="http://XXX/sun/commands/man.html">man</A> <A href="http://XXX/sun/commands/page.html">page</A>.
The <A href="http://XXX/sun/commands/snoop.html">snoop</A> command must be run by root (#) to capture packets to and from the default interface in <A href="http://www.skywayradio.com/tech/network/network_interface.html#promiscuous">promiscuous mode</A>. In summary form, only the data pertaining to the highest-level protocol is displayed. For example, an NFS packet only displays NFS information. The underlying RPC, <A href="http://XXX/network/index.html#UDP">UDP</A>, IP, and Ethernet frame information is suppressed but can be displayed if either of the verbose options is chosen.
The <A href="http://XXX/sun/commands/snoop.html">snoop</A> capture file format is described in RFC 1761. To access, use your favorite web browser with the URL: http://ds.internic.net/rfc/rfc1761.txt.
<A href="http://XXX/sun/commands/snoop.html">snoop</A> server client <A href="http://XXX/pages/commands/rpc.html">rpc</A> rstatd collects all RPC traffic between a client and server, and filters it for rstatd.
How to Check All Packets from Your System
*Become superuser.
*Type the following command at the command <A href="http://XXX/sun/commands/line.html">line</A> prompt to <A href="http://XXX/sun/commands/find.html">find</A> the interfaces attached to the system.
- <A href="http://XXX/sun/commands/netstat.html">netstat</A> -i
Snoop normally uses the first non-loopback device (le0).
*Type <A href="http://XXX/sun/commands/snoop.html">snoop</A>. Use Ctl-C to <A href="http://XXX/pages/commands/halt.html">halt</A> the process.
# <A href="http://XXX/sun/commands/snoop.html">snoop</A><BR></BR>Using device /dev/le (<A href="http://www.skywayradio.com/tech/network/network_interface.html#promiscuous">promiscuous mode</A>)<BR></BR> maupiti -> atlantic-82 NFS C GETATTR FH=0343<BR></BR> atlantic-82 -> maupiti NFS R GETATTR OK<BR></BR> maupiti -> atlantic-82 NFS C GETATTR FH=D360<BR></BR> atlantic-82 -> maupiti NFS R GETATTR OK<BR></BR> maupiti -> atlantic-82 NFS C GETATTR FH=1A18<BR></BR> atlantic-82 -> maupiti NFS R GETATTR OK<BR></BR> maupiti -> (broadcast) ARP C Who is 120.146.82.36, npmpk17a-82 ?<BR></BR><BR></BR>
* Interpret the results.
In the example, client maupiti transmits to server atlantic-82 using NFS file handle 0343. atlantic-82 acknowledges with OK. The conversation continues until maupiti broadcasts an ARP request asking who is 120.146.82.36?
This example demonstrates the format of <A href="http://XXX/sun/commands/snoop.html">snoop</A>. The next step is to filter <A href="http://XXX/sun/commands/snoop.html">snoop</A> to capture packets to a file.
Interpret the capture file using details described in RFC 1761. To access, use your favorite web browser with the URL: http://ds.internic.net/rfc/rfc1761.txt
How to Capture <A href="http://XXX/sun/commands/snoop.html">snoop</A> Results to a File
*Become superuser.
On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command.
- <A href="http://XXX/sun/commands/snoop.html">snoop</A> -o <A href="http://www.skywayradio.com/tech/ebooks/unix/upt/Filenames.html">filename</A>
For example:
# <A href="http://XXX/sun/commands/snoop.html">snoop</A> -o /tmp/cap<BR></BR>Using device /dev/le (<A href="http://www.skywayradio.com/tech/network/network_interface.html#promiscuous">promiscuous mode</A>)<BR></BR>30 <A href="http://XXX/sun/commands/snoop.html">snoop</A>: 30 packets captured<BR></BR>
This has captured 30 packets in a file /tmp/cap. The file can be anywhere with enough disk space. The number of packets captured is displayed on the command <A href="http://XXX/sun/commands/line.html">line</A>, enabling you to press Ctl-C to abort at any time.
<A href="http://XXX/sun/commands/snoop.html">snoop</A> creates a noticeable networking load on the <A href="http://XXX/sun/config.html#hosts">host</A> machine, which can distort the results. To see reality at work, run <A href="http://XXX/sun/commands/snoop.html">snoop</A> from a third system, (see the next section).
On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command to inspect the file.
- <A href="http://XXX/sun/commands/snoop.html">snoop</A> -i <A href="http://www.skywayradio.com/tech/ebooks/unix/upt/Filenames.html">filename</A>
For example:
# <A href="http://XXX/sun/commands/snoop.html">snoop</A> -i /tmp/cap<BR></BR> 1 0.00000 frmpk17b-082 -> 224.0.0.2 IP D=224.0.0.2 S=129.146.82.1 LEN=32, ID=0<BR></BR>2 0.56104 scout -> (broadcast) ARP C Who is 129.146.82.63, grail ?<BR></BR>3 0.16742 atlantic-82 -> (broadcast) ARP C Who is 129.146.82.76, honeybea ?<BR></BR>4 0.77247 scout -> (broadcast) ARP C Who is 129.146.82.63, grail ?<BR></BR>5 0.80532 frmpk17b-082 -> (broadcast) ARP C Who is 129.146.82.92, holmes ?<BR></BR>6 0.13462 scout -> (broadcast) ARP C Who is 129.146.82.63, grail ?<BR></BR>7 0.94003 scout -> (broadcast) ARP C Who is 129.146.82.63, grail ?<BR></BR>8 0.93992 scout -> (broadcast) ARP C Who is 129.146.82.63, grail ?<BR></BR>9 0.60887 towel -> (broadcast) ARP C Who is 129.146.82.35, udmpk17b-82 ?<BR></BR>10 0.86691 nimpk17a-82 -> 129.146.82.255 RIP R (1 destinations)<BR></BR>
Refer to specific protocol documentation for detailed analysis and recommended parameters for ARP, IP, RIP and so forth. Searching the Web is a good place to <A href="http://XXX/sun/commands/look.html">look</A> at RFCs.
How to Check Packets Between Server and Client
Establish a <A href="http://XXX/sun/commands/snoop.html">snoop</A> system off a hub connected to either the client or server.
The third system (the <A href="http://XXX/sun/commands/snoop.html">snoop</A> system) sees all the intervening traffic, so the snoop trace reflects reality on the wire.
*Become superuser. *On the command <A href="http://XXX/sun/commands/line.html">line</A>, type <A href="http://XXX/sun/commands/snoop.html">snoop</A> with options and save to a file. *Inspect and interpret results.
Look at RFC 1761 for details of the <A href="http://XXX/sun/commands/snoop.html">snoop</A> capture file. To access, use your favorite web browser with the URL: http://ds.internic.net/rfc/rfc1761.txt
Use <A href="http://XXX/sun/commands/snoop.html">snoop</A> frequently and consistently to get a feel for normal system behavior. For assistance in analyzing packets, <A href="http://XXX/sun/commands/look.html">look</A> for recent white papers and RFCs, and seek the advice of an expert in a particular area, such as NFS or YP. For details on using snoop and its options, <A href="http://XXX/sun/commands/refer.html">refer</A> to the <A href="http://XXX/sun/commands/snoop.html">snoop</A>(1M) <A href="http://XXX/sun/commands/man.html">man</A> <A href="http://XXX/sun/commands/page.html">page</A>.
<A class name="routing"></A>==Displaying Routing Information==
Use the <A href="http://XXX/sun/commands/traceroute.html">traceroute</A> utility to trace the <A href="http://XXX/sun/commands/route.html">route</A> an IP packet follows to some internet <A href="http://XXX/sun/config.html#hosts">host</A>. The traceroute utility utilizes the IP protocol time(to live) ttl field and attempts to elicit an <A href="http://en.wikipedia.org/wiki/ICMP">ICMP</A> TIME_EXCEEDED response from each <A href="http://XXX/pages/commands/gateway.html">gateway</A> along the path, and the response PORT_UNREACHABLE (or <A href="http://www.skywayradio.com/tech/ebooks/networking/tshoot/ch03_03.htm">ECHO_REPLY</A>) from the destination host. The traceroute utility starts sending probes with a ttl of one and increases by one until it gets to the intended <A href="http://XXX/sun/config.html#hosts">host</A> or has passed through a maximum number of intermediate <A href="http://XXX/sun/commands/hosts.html">hosts</A>.
The <A href="http://XXX/sun/commands/traceroute.html">traceroute</A> utility is especially useful for determining routing misconfiguration and routing path failures. If a particular <A href="http://XXX/sun/config.html#hosts">host</A> is unreachable, you can use the traceroute utility to see what path the packet follows to the intended host and where possible failures might occur.
The <A href="http://XXX/sun/commands/traceroute.html">traceroute</A> utility also displays the round trip time for each <A href="http://XXX/pages/commands/gateway.html">gateway</A> along the path to the target <A href="http://XXX/sun/config.html#hosts">host</A>. This information can be useful for analyzing where traffic is slow between the two <A href="http://XXX/sun/commands/hosts.html">hosts</A>.
How to Run the Traceroute Utility
On the command <A href="http://XXX/sun/commands/line.html">line</A>, type the following command.
% <A href="http://XXX/sun/commands/traceroute.html">traceroute</A> destination-hostname
Example -- traceroute Utility
The following sample of the <A href="http://XXX/sun/commands/traceroute.html">traceroute</A> command shows the 7-hop path a packet follows from the <A href="http://XXX/sun/config.html#hosts">host</A> istanbul to the host sanfrancisco along with the times for a packet to traverse each hop.
istanbul% <A href="http://XXX/sun/commands/traceroute.html">traceroute</A> sanfrancisco <A href="http://XXX/sun/commands/traceroute.html">traceroute</A>: Warning: Multiple interfaces found; using 172.31.86.247 @ le0 <A href="http://XXX/sun/commands/traceroute.html">traceroute</A> to sanfrancisco (172.29.64.39), 30 hops max, 40 byte packets<BR></BR> 1 frbldg7c-86 (172.31.86.1) 1.516 ms 1.283 ms 1.362 ms 2 bldg1a-001 (172.31.1.211) 2.277 ms 1.773 ms 2.186 ms 3 bldg4-bldg1 (172.30.4.42) 1.978 ms 1.986 ms 13.996 ms 4 bldg6-bldg4 (172.30.4.49) 2.655 ms 3.042 ms 2.344 ms 5 ferbldg11a-001 (172.29.1.236) 2.636 ms 3.432 ms 3.830 ms 6 frbldg12b-153 (172.29.153.72) 3.452 ms 3.146 ms 2.962 ms 7 sanfrancisco (172.29.64.39) 3.430 ms 3.312 ms 3.451 ms
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