Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Traceroute!!!!

 

 Hi,

 While tracing some destination, I have always observed that I am getting three times. Why so? I am giving one example below. I have tried to trace google.co.in and got mentioned output. Please reply.

 

C:\Users\nbgiripr>tracert google.co.in

Tracing route to google.co.in [173.194.112.87]
over a maximum of 30 hops:

  1     2 ms     3 ms    <1 ms  10.127.161.2
  2     1 ms     1 ms     1 ms  10.127.160.2
  3     6 ms     5 ms     7 ms  212.31.208.246

Regards

Ajit

3 REPLIES
New Member

I think when you are tracing

I think when you are tracing route to some ip address, it actually pings for 3 times to the next hop and gives the corresponding reply time for each ping. Like, by default, when you try to ping any ip address it gives you reply for 4 times in the same way tracert gives you 3 replys for each hop.

Super Bronze

DisclaimerThe Author of this

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

It's because the default is often 3 probes.  On many Cisco devices you can vary the number of probes.

Copied from this Cisco

Copied from this Cisco Article which explains both Ping and Traceroute:

http://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/ios-software-releases-121-mainline/12778-ping-traceroute.html

 

 

The Traceroute Command

The traceroute command is used to discover the routes that packets actually take when traveling to their destination. The device (for example, a router or a PC) sends out a sequence of User Datagram Protocol (UDP) datagrams to an invalid port address at the remote host.

Three datagrams are sent, each with a Time-To-Live (TTL) field value set to one. The TTL value of 1 causes the datagram to "timeout" as soon as it hits the first router in the path; this router then responds with an ICMP Time Exceeded Message (TEM) indicating that the datagram has expired.

Another three UDP messages are now sent, each with the TTL value set to 2, which causes the second router to return ICMP TEMs. This process continues until the packets actually reach the other destination. Since these datagrams are trying to access an invalid port at the destination host, ICMP Port Unreachable Messages are returned, indicating an unreachable port; this event signals the Traceroute program that it is finished.

 

 

74
Views
0
Helpful
3
Replies
CreatePlease login to create content