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OSPF debug Commands
The debug privileged EXEC commands can provide a wealth of information about the traffic and events being seen (or not seen) to include but not limited to, interface traffic, error messages generated by nodes on the network, protocol-specific diagnostic packets, and other useful troubleshooting data.
Exercise extreme care when using debug commands. Many of these commands are processor-intensive and can cause serious network problems (such as degraded performance or loss of connectivity) if they are enabled on an already heavily loaded router. When you finish using a debug command, remember to disable it with its specific no debug command (or use the no debug all command to turn off all debugging).
When to Use debug Commands
Only use debug commands to isolate problems, not to monitor normal network operation. Because the high overhead of debug commands can disrupt router operation, you should use debug commands only when you are looking for specific types of traffic or problems and have narrowed your problems to a likely subset of causes.
There are a quite a few debug commands available to you. The following is an example of only the IP-based debug commands that you might use.
OSPF_Router# debug ip ? bgp BGP information cache IP cache operations cgmp CGMP protocol activity dvmrp DVMRP protocol activity egp EGP information eigrp IP-EIGRP information error IP error debugging http HTTP connections icmp ICMP transactions igmp IGMP protocol activity igrp IGRP information mcache IP multicast cache operations mobile Mobility protocols mpacket IP multicast packet debugging mrouting IP multicast routing table activity ospf OSPF information packet General IP debugging and IPSO security transactions peer IP peer address activity pim PIM protocol activity policy Policy routing rip RIP protocol transactions routing Routing table events sd Session Directory (SD) security IP security options tcp TCP information udp UDP based transactions
The format of the output varies with each different debug command:
- Some debug commands generate a single line of output per packet, and others generate multiple lines of output per packet.
- Some debug commands generate large amounts of output, and others generate only occasional output.
- Some debug commands generate lines of text, and others generate information in field format.
How to Use debug Commands
Adhering to the following procedure minimizes the load created by using debug commands because the console port no longer has to generate character-by-character processor interrupts.
To minimize the negative impact on your router of using debug commands, follow this procedure:
- 1. Use the no logging console global configuration command on your router. This command disables all logging to the console terminal.
- 2. Telnet to a router port and enter the enable EXEC mode.
- 3. Use the terminal monitor command to copy debug command output and system error messages to your current terminal display. This permits you to view debug command output remotely, without being connected through the console port.
- 4. Open another Telnet session with the router and type the command undebug all in this second session but do not hit return. Then you start the debug session in the first session. When you are ready to stop the debug session go back to the second session and just press return to send the command. Eventually the routers CPU will process the command and shut off debug.
If you intend to keep the output of the debug command, spool the output to a file. The procedure for setting up such a debug output file is described in Ciscos Debug Command Reference publication. There are also certain programs that offer the capability to log everything displayed in your current Telnet session. The Windows Telnet application is a good example of a program with this capability.
Complete OSPF debug Commands
This book refers to specific debug commands that are useful when troubleshooting OSPF-specific related problems. Complete details regarding the function and output of debug commands are provided in Ciscos Debug Command Reference publication.
debug is a useful command that has many different options available for its use. It also provides you with a lot of information on what is going on within a router. However, it also can hurt the routing processes and normal operation of the router, so use it wisely.
The following is a list of the different types of debug commands:
- debug ip ospf ?. Provides help for debug ip ospf commands
- debug ip ospf adj. Deals with OSPF adjacency events
- debug ip ospf events. Deals with OSPF events
- debug ip ospf flood. Deals with OSPF flooding
- debug ip ospf lsa-generation. Deals with OSPF lsa generation
- debug ip ospf packet. Deals with OSPF packets
- debug ip ospf retransmission. Deals with OSPF retransmission events
- debug ip ospf spf. Deals with OSPF spf
- debug ip ospf tree. Deals with OSPF database tree
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