Command Line Utilities

 

Command Line Utilities: debugs, conditional debugs, traceroute, ping

ping

The ping tool uses the IP ICMP echo request and echo reply messages to test reachability to a remote system. In its simplest form, ping simply confirms that an IP packet is capable of getting to and getting back from a destination IP address

Ping is a command used to measure the latency between two devices on a network. The ping command is available on every operating system and is a measure of the latency we feel

traceroute

The traceroute utility sends out either ICMP echo request (Windows) or UDP (most implementations) messages with gradually increasing IP TTL values to probe the path by which a packet traverses the network .The tracert command is a Command Prompt command that’s used to show several details about the path that a packet takes from the computer or device you’re on to whatever destination you specify.

You might also sometimes see the tracert command referred to as the trace route command or traceroute command.

Traceroute is a useful tool for determining the response delays and routing loops present in a network pathway across packet switched nodes. It also helps to locate any points of failure encountered while en route to a certain destination

Conditional debugging is used to filter out the debug information so that the CPU consumption by debug is lowered significantly. It allows us to show debug information that matches a certain interface, MAC address etc.

R1#debug condition ?
  application  Application
  called       called number
  calling      calling
  card         card
  glbp         interface group
  interface    interface
  ip           IP address
  mac-address  MAC address
  match-list   apply the match-list
  standby      interface group
  username     username
  vcid         VC ID
  vlan         vlan
  voice-port   voice-port number
  xconnect     Xconnect conditional debugging on segment pair

This is quite a list with different items to choose from. I’ll use the interface as a condition:

R1#debug condition interface fastEthernet 0/0
Condition 1 set

Using this debug condition we will only see RIP debug information from the FastEthernet 0/0 interface:

R1#
RIP: sending v2 update to 224.0.0.9 via FastEthernet0/0 (192.168.12.1)
RIP: build update entries
	192.168.13.0/24 via 0.0.0.0, metric 1, tag 0

The debug ip rip command is an excellent command to use to examine the contents of the routing updates that are sent and received by a router. There may be times when a route is being received by a router but is not being added to the routing table.

 One reason for this could be that a static route is also configured for the same network being advertised. By default, a static route has a lower administrative distance than any dynamic routing protocol and will take precedence in being added to the routing table.