Traceroute: different results

Question

I was testing traceroute between two servers (single hop only) and I wonder why subsequent run shows different results?

(1)

# traceroute to 172.22.10.12 (172.22.10.12), 30 hops max, 60 byte packets
 1  172.22.10.12  0.167 ms  0.634 ms  0.152 ms

(2)

# traceroute to 172.22.10.12 (172.22.10.12), 30 hops max, 60 byte packets
     1  * * *
     2  * * *
     3  * * *
     4  * * *
     5  * * *
     6  * 172.22.10.12  0.120 ms  0.094 ms

EDIT: Wed Dec 18 18:09:23 GMT 2013

Why this question has negative votes? I would like to know why traceroute shows different results (the number of hops) each time.

EDIT: Wed Dec 18 19:05:44 GMT 2013

Both servers are connected to a single switch so there is no any 'routing' and path should be the same:

# ping -R -c 5 172.22.10.12
PING 172.22.10.12 (172.22.10.12) 56(124) bytes of data.
64 bytes from 172.22.10.12: icmp_seq=1 ttl=64 time=0.161 ms
RR:     172.22.10.10
    172.22.10.12
    172.22.10.12
    172.22.10.10

64 bytes from 172.22.10.12: icmp_seq=2 ttl=64 time=0.470 ms (same route)
64 bytes from 172.22.10.12: icmp_seq=3 ttl=64 time=0.113 ms (same route)
64 bytes from 172.22.10.12: icmp_seq=4 ttl=64 time=0.162 ms (same route)
64 bytes from 172.22.10.12: icmp_seq=5 ttl=64 time=0.160 ms (same route)

--- 172.22.10.12 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4001ms
rtt min/avg/max/mdev = 0.113/0.213/0.470/0.130 ms

You should post a second, different copy of the results you are getting. — Bert, Dec 18 '13 at 18:27
It's a single hop? There's no routing being done between the hosts, is that correct? — mfinni, Dec 18 '13 at 18:47
What is the IP of the source server you are running the traceroute/ping from? — Rex, Dec 18 '13 at 19:14

score 3 · Answer 1 · answered Dec 18 '13 at 21:05

The second traceroute, with the 5 sets of * * * , does not indicate a different path. You've told us that you know there isn't another path, these things are in the same L2 domain and even on the same switch. Tracert will never show an intermediate hop, and in fact it is not doing so in this case.

For whatever reason, your target host isn't replying to ICMP the first few tries on that second tracert. That is all that you're seeing. Maybe it's too busy to reply to ICMP? That's one reason that simple ping tests aren't good determiners of a service being up or down.

(I have no idea why you're using a L3 tool to show some behavior that has nothing to do with L3. )

score 2 · Answer 2 · answered Dec 18 '13 at 18:39

2

IP traffic does not necessarily follow the same path. So in the case of traceroute that is sending ICMP packets they don't always necessarily follow the same path too (ICMP runs on top of IP)

There's a whole wikipedia entry on traceroute

Hope this helps.

answered Dec 18 '13 at 18:39

Rico

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Both servers are connected to the same switch. – HTF Dec 18 '13 at 19:11
But your questions states "tested with different servers/locations" so which is it? – Rex Dec 18 '13 at 19:13
on your edit your are running ping and not traceroute. Where does the traceroute going as a first hop in the case where they are different ? – Rico Dec 18 '13 at 19:16
It's the same location and I used `PING` to indicate that it's the `same route` – HTF Dec 18 '13 at 19:25

Traceroute: different results

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