Information Technology Reference
In-Depth Information
Using the trace Commands
The
trace
user exec command discovers the routes that a router's packets follow when travelling to their
destinations. The
trace
privileged exec command permits the supported IP header options to be
specified, allowing the router to perform a more extensive range of test options.
The
trace
command works by using the error message generated by routers when a datagram exceeds
its time-to-live (TTL) value. First, probe datagrams are sent with a TTL value of 1. This causes the first
router to discard the probe datagrams and send back “time exceeded” error messages. The
trace
command then sends several probes and displays the round-trip time for each. After every third probe,
the TTL is increased by 1.
Each outgoing packet can result in one of two error messages. A “time exceeded
”
error message
indicates that an intermediate router has seen and discarded the probe. A “port unreachable” error
message indicates that the destination node has received the probe and discarded it because it could not
deliver the packet to an application. If the timer goes off before a response comes in,
trace
prints an
asterisk (
*
).
The
trace
command terminates when the destination responds, when the maximum TTL is exceeded, or
when the user interrupts the trace with the escape sequence.
As with
ping
, it is a good idea to use the
trace
command when the network is functioning properly to
see how the command works under normal conditions and so that you have something to compare against
when troubleshooting.
For detailed information on using the
trace
and extended
trace
commands, refer to the
Cisco IOS
Configuration Fundamentals Command Reference
.
Using Cisco Network Management Tools
Cisco offers the CiscoWorks 2000 family of management products that provide design, monitoring, and
troubleshooting tools to help you manage your internetwork.
The following internetwork management tools are useful for troubleshooting internetwork problems:
•
CiscoView provides dynamic monitoring and troubleshooting functions, including a graphical
display of Cisco devices, statistics, and comprehensive configuration information.
•
Internetwork Performance Monitor (IPM) empowers network engineers to proactively troubleshoot
network response times utilizing real-time and historical reports.
•
The TrafficDirector RMON application, a remote monitoring tool, enables you to gather data,
monitor activity on your network, and find potential problems.
•
The VlanDirector switch management application is a management tool that provides an accurate
picture of your VLANs.
CiscoView
CiscoView
graphical management features provide dynamic status, statistics, and comprehensive
configuration information for Cisco internetworking products (switches, routers, hubs, concentrators,
and access servers). CiscoView aids network management by displaying a physical view of Cisco
devices and color-coding device ports for at-a-glance port status, allowing users to quickly grasp
essential information. Features include the following:
