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CCNA 7.6.a: Ping and traceroute with extended option

Overview:

Extended ping and extended traceroute commands are used to perform more advanced checks of host reachability and network connectivity

 

Study Notes:

 

Standard Ping

  • The ping command is used to test and troubleshoot the accessibility of devices
  • The ping command first sends an echo request packet to an address, and then it waits for a reply.
  • The ping is successful only if the ECHO REQUEST gets to the destination, and the destination is able to get an ECHO REPLY back to the source of the ping within a predefined time interval.
  • Standard ping uses the IP address of the interface the packets use to exit the router
  • Standard ping works in user EXEC and  privileged EXEC mode
  • The standard ping command is:
Router#ping 192.168.1.2

 

Extended Ping

  • Extended ping provides the ability to change the source IP address to any interface that is up on the router
  • Extended ping therefore allows you to verify that routing is configured correctly on your router by using a source IP other than that of the exit interface
  • Extended ping works only in privileged EXEC mode
  • Enter the ping command without any other options to be prompted for the extended ping command fields
Router>enable
Router#ping
Protocol [ip]:
Target IP address: 192.168.1.2
Repeat count [5]: 10
Datagram size [100]: 1500
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: 172.16.1.1
Type of service [0]:
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 10, 1500-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (10/10), round-trip min/avg/max = 34/89/121 ms  

!--- Ping is successful.
Router#

 

  • You may also enter the extended switches and commands via a single string on the command line
  • The command entered via the prompts above would look like this on the command line
Router#ping 192.168.1.2 source 172.16.1.1 repeat 10 size 1500

 

Standard Traceroute

  • While ping is used to test connectivity to another device, traceroute is used to discover the path packets take to a remote destination
  • When traceroute doesn't make it to the destination you can see based on the output where the routing is failing
  • Traceroute records the source of each ICMP "time exceeded" message
  • The device that executes the traceroute sends out a series of UDP datagrams, each with incrementing TTL values
  • Traceroutes are sent to an invalid port address 33434
  • The first three datagrams in a traceroute are sent with a TTL of 1 so that they exceed the TTL at the first hop in the path to the destination network
  • The next three datagrams are sent with a TTL of 2 so that they exceed the TTL at the second hop in the path to the destination network
  • This process continues until the traceroutes reach the remote destination
  • Standard traceroute works in user EXEC and  privileged EXEC mode
  • The standard traceroute command is:
Router#traceroute 192.168.1.2

 

Extended Traceroute

  • Extended traceroute is used to see which path the packets take to get to the destination network
  • Routing loops can be more easily detected with the extended traceroute command
  • Extended traceroute is useful to see at which device packets are getting lost due to a missing route or packets are getting blocked due to an ACL
  • Use extended ping and extended traceroute commands together to determine what type of connectivity issue you have and determine on which device the issue exists
  • When the extended ping timer goes off before a response comes back, an asterisk (*) is printed on the CLI display
  • Extended traceroute works only in privileged EXEC mode
  • Enter the traceroute command without any other options to be prompted for the extended traceroute command fields
Router>enable
Router#traceroute
Protocol [ip]:
Target IP address: 192.168.1.2
Source address: 172.16.1.1
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:10
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 192.168.1.2

  1 172.18.2.2 16 msec 19 msec 19 msec
  2 172.20.20.2 28 msec 30 msec 32 msec
  3 192.168.1.2 32 msec 25 msec *   

!--- The traceroute is successful.


Router#

 

  • You may also enter the extended switches and commands via a single string on the command line
  • The command entered via the prompts above would look like this on the command line
Router#traceroute 192.168.1.2 source 172.16.1.1 ttl 1 10

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