Points to Remember

• The ping command is a diagnostic tool to test connectivity of hosts in a TCP/IP network and isolate TCP/IP network problems.

• The user exec mode is used to perform a simple TCP/IP network connectivity test.

• Parameters of the ping command in the user exec mode are protocol, host name, and address.

• The privilege exec mode, also known as an extended ping, is used to perform a detailed check of TCP/IP network connectivity.

• Different parameters of the ping command in the privilege exec mode are protocol, target IP address, repeat count [5], datagram size [100], timeout in seconds [2], and extended commands [n].

• The trace command is a diagnostic tool to trace the path between two hosts to locate any connectivity problems.

• The parameters of the trace command are host name and host address.

• The trace command ends when the destination host replies on receipt of a packet, the maximum TTL value of 30 is exceeded, or a user interrupts the trace command by using the escape sequence.

• The show command is a diagnostic tool to determine the exact cause of a performance slowdown in a TCP/IP network.

• The show ip route command displays records in the IP routing table.

• The show ip ospf command displays detailed information regarding OSPF ports and interfaces.

• The show ip ospf interface command displays information regarding the interfaces on which OSPF is running .

• The show ip ospf neighbor command is used to display information regarding the neighboring routers connected with OSPF.

• The show ip access-list command is used to display information regarding specific or all current IP access lists in the 1 to 99 range.

• The show ip arp command displays information present in the router’s ARP cache.

• The show ip protocols command displays information regarding IP routing protocols that are executed on the router.

• The show ip traffic command displays information collected by the router regarding IP traffic.

• The debug ip rip command displays information regarding RIP routing transactions that are sent by a serial interface.

• The debug ip icmp command enables you to determine if the router is sending and receiving ICMP messages.

• The debug ip packet command displays all the IP debugging information and IP security options.

• The debug arp command checks the flow of data at the ARP.

• RIP takes a longer time to converge than IGRP.

• To counter unsecured exchange of routing information and routing loops, use the default-metric or redistribute protocol metric command.

• To check if a TCP/IP network is working properly, execute the loopback ping command.

• Use the Tracert tool to trace a TCP/IP packet crossing its way to the destination.