7.6 Use Cisco IOS tools to troubleshoot and resolve problems
7.6.a Ping and traceroute with extended option
Extended pings and traceroutes can be performed to verify the internal routing table of the device. For example you can ping from and interarea interface by simply typing “ping” only and specifying a source address
Router#ping Protocol [ip]: Target IP address: 192.168.0.1 Repeat count : Datagram size : 999 Timeout in seconds : 1 Extended commands [n]: y Source address or interface: 10.0.0.1 Type of service : 3 Set DF bit in IP header? [no]: Validate reply data? [no]: Data pattern [0xABCD]: Loose, Strict, Record, Timestamp, Verbose[none]: Sweep range of sizes [n]: Type escape sequence to abort. Sending 5, 999-byte ICMP Echos to 192.168.0.1, timeout is 1 seconds: Packet sent with a source address of 10.0.0.1 ..... Success rate is 0 percent (0/5)
In this case the ping failed due to the receiver not knowing the route to R1’s loopback.
Typing “traceroute” with no options will allow the extended option:
Router#traceroute Protocol [ip]: Target IP address: 126.96.36.199 Source address: 192.168.0.200 Numeric display [n]: Timeout in seconds : Probe count : Minimum Time to Live : Maximum Time to Live : Port Number : Loose, Strict, Record, Timestamp, Verbose[none]: Type escape sequence to abort. Tracing the route to 188.8.131.52 1 * * * 2 * * * 3 * * *
7.6.b Terminal monitor
Unless you login via the console port, terminal logging is disabled by default. To enable console messages in a SSH session enter “terminal monitor” in EXEC mode.
7.6.c Log events
Logs can be triggered by ACLs by placing “log” at the end of the acl configuration command.
7.6.d Local SPAN
A switch can be configured with a monitoring session that will cause the switch to forward traffic to a specified port.
This allow the technician to use a capture packet tool such as Wireshark to troubleshoot network connectivity problems. GNS3 doens’t support SPAN so I guess I will have to skip over this lab.