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To fully utilize the configurable options of a trace you need to understand what each option allows you to do, as explained in the following list.
- Target IP address:. This option enables you to enter a host name or an IP address; there is no default.
- Source address:. This option indicates the IP address on the source router. As a default, the router will randomly determine the best.
- Numeric display:. The default for this option is to have both symbolic (names) and numeric displays of IP addresses.
- Timeout in seconds:. This option determines the number of seconds to wait for a response to a probe packet. The default is 3 seconds.
- Probe count:. This option sets the number of probes to be sent at each TTL level; the default is 3.
- Minimum time to live :. This option sets the TTL value for the first probes; the default is 1, but it can be set to a higher value.
- Maximum time to live :. This option sets the largest TTL value that can be used; the default is 30.
- Port number:. This option sets the destination port used by the UDP probe messages, default is 33434.
- Loose, Strict, Record, Timestamp, Verbose:. These are the various IP header options. You can specify any combination. The trace command issues prompts for the required fields. trace places the requested options in each probe, but there is no guarantee that all routers (or end nodes) will process the options you selected.
- Loose. This option allows you to specify a list of nodes that must be traversed when going to the destination selected. Think of its operation like this: You can take any path to the destination but it must include this specific set of routers.
When you specify the routers for the loose option, be aware that the trace probe will follow the path as indicated in the sequence specified. If you specify a router on the other side of the network and then the one you are in, trace will send the probe out then come back your router and proceed along to the destination. This means you could make trace ping pong between two or more routers.
- Strict. This option allows you to specify a list of nodes to traverse when going to the destination. Think of its operation like this: his is the only path you can take to reach the destination. This strict path is based upon the node addresses you enter and their order. One final note, the nodes entered must also be sequentially adjacent (i.e. one hop apart from each other).
- Record. This option allows you to specify the number of hops to leave room for, but the IP header will not support more than nine hops.
- Timestamp. This option allows you to specify the number of timestamps to leave room for. You may specify up to nine timestamp slots. The time is recorded according to the remote routers clock. If you are concurrently using the record option, then no more than four hops will be recorded. (The IP option header space is shared by record route and timestamp.)
- Verbose. If you select any option, the verbose mode is automatically selected and trace prints the contents of the option field in any incoming packets. You can prevent verbose mode by selecting verbose again, toggling its current setting.
An interesting point of note is that the verbose option is Cisco-specific. The trace command will place the appropriate options in each packet; unfortunately, there is no guarantee that all routers will process the options.
Cisco Technical Support
When you have a problem that you cannot resolve, the resource of last resort is your Cisco Systems technical support representative. To analyze problem, your technical support representative will need certain information about the situation and the symptoms you are experiencing. To speed the problem isolation and resolution process, present the data discussed in the following sections when you contact your representative.
Gathering Network Information
Before gathering any specific data, compile a list of all symptoms that users have reported on the internetwork (such as connections dropping or slow host response).
The next step is to gather specific information. Typical information needed to troubleshoot internetworking problems falls into two general categories: information required for any situation and information specific to the topology, technology, protocol, or problem.
Information that is always required by technical support engineers includes the following:
- Configuration listing of all routers involved
- Complete specifications of all routers involved
- Version numbers of software (obtained with show version command) and firmware (obtained with the show controllers command) on all relevant routers
- Network topology map
- List of hosts and servers (host and server type, number on network, description of host operating systems implemented)
- List of network layer protocols, versions, and vendors
To assist you in gathering this required data, the show tech-support EXEC command has been added in Cisco IOS Release 11.1(4) and later. This command provides general information about the router that you can provide to your technical support representative when you are reporting a problem.
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