Re: Understanding traceroute results ...

sanjay.nadarajah · ‎05-11-2010

Hi,

I have a very unique traceroute results which does not make too much sense to me.

Here are the traceroute results :-

1) On the switch that connects the site to the MPLS cloude :-

Traceroute #1 From switch S

Switch> (enable) traceroute 10.49.50.181

traceroute to 10.49.50.181 (10.49.50.181), 30 hops max, 40 byte packets

1 10.49.71.1 (10.49.71.1) 8 ms 9 ms 6 ms

2 10.49.140.81 (10.49.140.81) 9 ms 30 ms 11 ms

3 10.49.140.58 (10.49.140.58) 9 ms 7 ms 7 ms

4 10.49.53.1 (10.49.53.1) 15 ms 8 ms 10 ms

5 10.49.50.181 (10.49.50.181) 7 ms 8 ms 15 ms

2) Traceroute #2 : A PC on Site A's Network

tracert 10.49.50.181

Tracing route to [10.49.50.181]

over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 10.49.71.1

2 5 ms 2 ms <1 ms 10.49.140.81

3 2 ms 2 ms 2 ms 10.49.140.58

4 2 ms 2 ms 2 ms 10.49.53.1

5 2 ms 2 ms 2 ms 10.49.50.181

The setup is :

*** DC --> MPLS Cloud --> Switch S --> PC ***

What I don't understand is the RTT on the PC is only 2ms to reach the DC but on the switch, a 4006 switch, the RTT time is much higher. The pc

is on a port on the 4006 switch.

Can anyone explain this to me ?

Cheers,

-sn-

Ganesh Hariharan · ‎05-11-2010

Hi,

I have a very unique traceroute results which does not make too much sense to me.

Here are the traceroute results :-

1) On the switch that connects the site to the MPLS cloude :-

Traceroute #1 From switch S

Switch> (enable) traceroute 10.49.50.181

traceroute to 10.49.50.181 (10.49.50.181), 30 hops max, 40 byte packets

1 10.49.71.1 (10.49.71.1) 8 ms 9 ms 6 ms

2 10.49.140.81 (10.49.140.81) 9 ms 30 ms 11 ms

3 10.49.140.58 (10.49.140.58) 9 ms 7 ms 7 ms

4 10.49.53.1 (10.49.53.1) 15 ms 8 ms 10 ms

5 10.49.50.181 (10.49.50.181) 7 ms 8 ms 15 ms

2) Traceroute #2 : A PC on Site A's Network

tracert 10.49.50.181

Tracing route to [10.49.50.181]

over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 10.49.71.1

2 5 ms 2 ms <1 ms 10.49.140.81

3 2 ms 2 ms 2 ms 10.49.140.58

4 2 ms 2 ms 2 ms 10.49.53.1

5 2 ms 2 ms 2 ms 10.49.50.181

The setup is :

*** DC --> MPLS Cloud --> Switch S --> PC ***

What I don't understand is the RTT on the PC is only 2ms to reach the DC but on the switch, a 4006 switch, the RTT time is much higher. The pc

is on a port on the 4006 switch.

Can anyone explain this to me ?

Cheers,

Hi,

Genrally the RTT defination says in trace route packet is each millisecond (ms) time in the table is the round-trip time that it took (to send the ICMP packet and to get the ICMP reply packet). The faster (smaller) the times the better. ms times of 0 mean that the reply was faster than the computers timer of 10 milliseconds, so the time is actually somewhere between 0 and 10 milliseconds.

RTT's reported are the round trip times from the source host to that router hop. It's not a cumulative sum of the previous times. Each hop is going to add some time to the path, so you'd expect each hop to take a little bit more time to get to than the last.

Hope that Help !!

Ganesh.H