|  | 7.3 | Troubleshooting Networks
| 7.3.3 | Software t ools

Along with the processes that are described above, there are software tools that are available for the network administrator to use to solve network connectivity problems. These tools can help in Local Area Network troubleshooting, but are especially helpful in a Wide Area Network troubleshooting situation. We will look at the commands that are available to a network administrator in most client software packages. These commands include the Ping, Tracert (Traceroute), Telnet, Netstat, ARP, and IPconfig (WinIPcfg). Ping Sends ICMP echo packets to verify connections to a remote host. The following output will display if the ping is successful. The output shows the number of packets responded to and the return time of the echo. Ping [-t] [-a] [-n count] [-l length] [-f] [-i ttl] [-r count] destination
-t | ping until interrupted
-a | resolves host name and ping address
-n | resolves host name and ping address
-l | length - send specified size echo packets
-f | DO NOT FRAGMENT command sent to gateways
-i | ttl sets the TTL field
-r | count records the route of the outgoing and returning packets
destination | specifies the remote host to ping, by domain name or by IP address
Tracert (Traceroute) This utility shows the route a packet took to reach its destination. The following output shows the trace command. Tracert [-d] [-h maximum_hops] [-j host-list] [-w timeout] target_name
-d | specifies IP addresses shouldn't be resolved to host names
-h | max_hops Maximum number of hops searched
-j | host-list specifies the loose source route
-w | timeout waits the number of milliseconds specified for each reply
Telnet This is a terminal emulation program that will allow you to run interactive commands on the telnet server. Until a connection is established, no data will pass and if the connection should break telnet will inform you. Good for testing login configuration parameters to a remote host. Telnet [destination (IP or DNS name)] Netstat Displays protocol statistics and current TCP/IP network connections. Netstat [-a] [-e] [-n] [-s] [-p proto] [-r] [interval]
-a | Displays all connections and listening ports. (Server-side connections are normally not shown).
-e | Displays Ethernet statistics. This may be combined with the -s option.
-n | Displays addresses and port numbers in numerical form.
-p proto | Shows connections for the protocol specified by proto; proto may be tcp or udp. If used with the -s option to display per-protocol statistics, proto may be tcp, udp, or ip.
-r | Displays the contents of the routing table.
-s | Displays per-protocol statistics. By default, statistics are shown for TCP, UDP and IP; the -p option may be used to specify a subset of the default.
interval | Redisplays selected statistics, pausing interval seconds between each display. Press CTRL+C to stop redisplaying statistics. If omitted, Netstat will print the current configuration information once.
ARP Used to gather hardware addresses of local hosts and the default gateway, you can view the ARP cache and check for invalid or duplicate entries arp -a [inet_addr] [-N [if_addr]] arp -d inet_addr [if_addr] arp -s inet_addr ether_addr [if_addr]
-a or -g | Displays the current contents of the arp cache
-d | Deletes the entry specified by inet_addr
-s | Adds a static entry to the cache
-N | Displays the arp entries for the specified physical address
inet_addr | IP address, in dotted decimal format
if_addr | IP address whose cache should be modified
ether_addr | The MAC address in hex separated by hyphens
IPconfig (Windows NT)/WinIPcfg (Windows 95-98) These Windows utilities display IP-addressing information for the local network adapter(s) or a specified NIC. IPconfig [/all | /renew [adapter] | /release [adapter]]
/all | all information about adapter(s)
/renew | renew DHCP lease information for all local adapters if none is named
/release | release DHCP lease information disabling TCP/IP on this adapter
These are the tools that will allow a network administrator to remotely monitor and control the network. It is important to implement the proper security when using SNMP and RMON so that the network is not violated.
| Lab Activity
This lab focuses "out-of-band" router management using the AUX port on the router and a modem.