Examples of Unsuccessful ping and traceroute Commands

Purpose

When the ping or traceroute commands are unsuccessful, it is useful to understand the output.

Action

To ping and traceroute between R5 and R6, enter the following JUNOS CLI operational mode commands:

user@host> ping interface-address count requests

user@host> traceroute interface-address

Sample Output 1

user@R6> ping 10.1.15.2 count 3

PING 10.1.15.2 (10.1.15.2): 56 data bytes

36 bytes from 10.1.26.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 3648   0 0000  01  01 465c 10.1.26.2  10.1.15.2 

36 bytes from 10.1.26.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 364b   0 0000  01  01 4659 10.1.26.2  10.1.15.2 

36 bytes from 10.1.26.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 364f   0 0000  01  01 4655 10.1.26.2  10.1.15.2 

^C

--- 10.1.15.2 ping statistics ---

3 packets transmitted, 0 packets received, 100% packet loss

user@R6> ping 10.0.0.5 count 3

PING 10.0.0.5 (10.0.0.5): 56 data bytes

ping: sendto: No route to host

ping: sendto: No route to host

ping: sendto: No route to host

^C

--- 10.0.0.5 ping statistics ---

3 packets transmitted, 0 packets received, 100% packet loss

user@R6> ping 10.1.15.2         

PING 10.1.15.2 (10.1.15.2): 56 data bytes

^C

--- 10.1.15.2 ping statistics ---

4 packets transmitted, 0 packets received, 100% packet loss

Sample Output 2

user@R6> traceroute 10.1.15.2 

traceroute to 10.1.15.2 (10.1.15.2), 30 hops max, 40 byte packets

 1  10.1.26.1 (10.1.26.1)  0.626 ms  0.526 ms  0.494 ms

 2  10.1.26.2 (10.1.26.2)  0.521 ms  0.529 ms  0.509 ms

 3  10.1.26.1 (10.1.26.1)  0.516 ms  0.536 ms  0.523 ms

 4  10.1.26.2 (10.1.26.2)  0.528 ms  0.547 ms  0.524 ms

 5  10.1.26.1 (10.1.26.1)  0.532 ms  0.549 ms  0.535 ms

 6  10.1.26.2 (10.1.26.2)  0.547 ms  0.566 ms  0.543 ms

 7  10.1.26.1 (10.1.26.1)  0.551 ms  0.569 ms  0.538 ms

 8  10.1.26.2 (10.1.26.2)  0.557 ms  0.580 ms  0.567 ms

 9  10.1.26.1 (10.1.26.1)  0.570 ms  0.598 ms  0.570 ms

user@R6> traceroute 10.1.15.2 

traceroute to 10.1.15.2 (10.1.15.2), 30 hops max, 40 byte packets

 1  10.1.36.1 (10.1.36.1)  0.651 ms  7.834 ms  0.506 ms

 2  10.1.23.1 (10.1.23.1)  0.536 ms  0.538 ms  0.504 ms

 3  * * *

 4  * * *

 5  *^C

What It Means

Sample output 1 shows three instances of the ping command not succeeding. In the first instance, the packets exceed the time-to-live value, which is decremented to 1, indicating that packets are being rejected possibly because of a loop. In the second instance, the local router does not know the route to the host. In the third instance, there is no route to the IP address, which might be due to packets being lost on a remote router.

Sample output 2 shows two instances of the traceroute command not succeeding. In the first instance, there is a loop between shared interfaces on R6 and R2, as indicated by the 10.1.26.1 and 10.1.26.2 appearing repeatedly. In the second instance, the path goes through R3 (10.1.36.1) to R2 (10.1.23.1) when it times out, as indicated by the asterisk (*). The timeout might be due to the absence of a route to the remote interface.