Technical data

Troubleshooting Techniques and Tools
1.2 Isolating Problems
• Does the problem affect a single user? Multiple users? Your LAN?
The following steps can help you isolate your problem and determine a solution.
1. Check connectivity. (Section 1.2.1)
2. Check network interface parameters. (Section 1.2.2)
3. Check the IP address to Ethernet address translation tables. (Section 1.2.3)
4. Examine network statistics. (Section 1.2.4)
5. Monitor network traffic. (Section 1.2.5)
6. Check name server operation. (Section 1.2.7)
7. Check the route to a remote host. (Section 1.2.8)
8. Check the routes known to a gateway. (Section 1.2.9)
9. Check whether the network services have been enabled. (Section 1.2.10)
10. Look for application errors or interoperability issues.
Table 1–1 summarizes the tools you use to obtain information about network
operations. The following sections describe each tool in detail.
Table 1–1 Diagnostic Tools
Diagnostic Tool Function
arp Controls and displays ARP tables.
dig Sends domain name query packets to name servers.
ifconfig Configures or displays network interface parameters, redefines
an address for a particular interface, or sets options such as
an alias list, broadcast address, or access filter. Use to detect
incorrect IP addresses, subnet masks, and broadcast addresses.
ndc
Allows the name server administrator to send messages to
a name server to start, stop, and restart BIND; to dump the
BIND database; to check the status of the BIND process; and
to change the tracing level.
netstat Displays network statistics of sockets, data link counters,
specified protocols or aliases, network interfaces, and a host’s
routing table.
nslookup Provides the ability to directly query a name server and
retrieve information. Use NSLOOKUP to determine whether
your local name server is running correctly or to retrieve
information from remote name servers.
ping Indicates a host is reachable, and displays statistics about
packet loss and delivery time.
route Allows the user to manipulate the network routing tables
manually.
sysconfig Displays and maintains the various network subsystem
attributes.
sysconfigdb Manages the subsystem configuration database.
tcpdump Provides dump analysis and packet tracing.
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1–2 Troubleshooting Techniques and Tools