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Tracert going via 2 Tunnels

Answered Question
Feb 21st, 2014
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Hi Everyone,


I was tracing a IP from my PC.


Here is setup                 172.31.250.19

                                        |

Site A  -----PC---SW1--SW2----Tunnel 1  to ------------Site2---SW1------Tunnel 2   -------------Site 3-----Router1-----Router2-------------IP 172.21.100.20

                               |

                            172.31.22.254


Where My PC is at Site 1

I am tracing IP of Router 1



Tracert shows it is 3 hops away


Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

U:\>tracert 172.20.100.21

Tracing route to 172.21.100.20 over a maximum of 30 hops

  1     5 ms    14 ms     6 ms  172.31.22.254--------------------------------IP of SW1 at site 1
  2    <1 ms    <1 ms    <1 ms  172.31.250.19----------------IP of Sw2 at site 1

3    67 ms    67 ms    68 ms  172.21.100.20-------------------------IP of SW1 at sie 2

Trace complete.

U:\>


i know that if traffic goes via single tunnel it does not show hops in between.


So does that mean that even if we have 3 or more tunnels in between source and destination IP tracert will show it as only 1 hop away?

as we have seen here that from SW2 at site 1 it is only 1 hop away?


Regards


Mahesh


Message was edited by: mahesh parmar

Correct Answer by Reza Sharifi about 3 years 6 months ago

Hi Mahesh,



So you have a tunnel-1 (router) to tunnel-2 (router) to tunnel-3 (router)?

Are the end points for each tunnel a router?

Can you add IPs to your diagram?

It maybe you enter tunnel-1 and then right into the second tunnel and out

can you clarify?


Reza

Correct Answer by Richard Burts about 3 years 6 months ago

Mahesh


What about this line from your original post

3    67 ms    67 ms    68 ms  172.21.100.20-------------------------IP of SW1 at sie 2


HTH


Rick


[edit] I think it would help if you would give us the diagram of this again and put IP addresses in the diagram for each of the device interfaces.

Also I realize that I have been assuming that the switches that you mention were operating as layer 3 routing devices. If the switch connected to R2 is actually a layer 2 switch then what you are seeing might be the correct behavior. So some more information about how things are configured would be helpful.

Correct Answer by Richard Burts about 3 years 6 months ago

Reza


In the original post Mahesh gives us this

172.21.100.20-------------------------IP of SW1 at sie 2


Mahesh


I do not understand your response. This time you are doing tracert 172.21.100.20, which is not quite the same as the tracert in your original post. And to 172.21.100.20 I believe that 3 hops is indeed the correct behavior.


HTH


Rick

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Richard Burts Sat, 02/22/2014 - 05:25
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Mahesh


I would say that this is not normal. If there are multiple tunnels then there should be a hop for each of the tunnels. I am a bit confused about your traceroute. I see that you entered this command

tracert 172.20.100.21

but then your PC says this

Tracing route to 172.21.100.20

and sure enough when it get to 172.21.100.20 the trace says complete.

So I believe that the issue is not about tunnels but is about what happened in your PC.


HTH


Rick

mahesh18 Sat, 02/22/2014 - 07:06
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Hi Rick,


These tunnels 1 and 2 are running over the ISP WAN links.


Here is new tracert from my pc


Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

U:\>tracert 172.21.100.20

Tracing route to 172.21.100.20 over a maximum of 30 hops

  1     5 ms    14 ms     6 ms  172.31.22.254
  2    <1 ms    <1 ms    <1 ms  172.31.250.19
  3    67 ms    67 ms    68 ms  172.21.100.20

Trace complete.


Now the tracert shows going to right IP.

Still it only shows 3 hops



Regards


Mahesh

Reza Sharifi Sat, 02/22/2014 - 07:39
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Hi Mahesh,


In your diagram, what device has IP 172.21.100.20


Thanks,

Reza

Correct Answer
Richard Burts Sat, 02/22/2014 - 08:11
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Reza


In the original post Mahesh gives us this

172.21.100.20-------------------------IP of SW1 at sie 2


Mahesh


I do not understand your response. This time you are doing tracert 172.21.100.20, which is not quite the same as the tracert in your original post. And to 172.21.100.20 I believe that 3 hops is indeed the correct behavior.


HTH


Rick

mahesh18 Sat, 02/22/2014 - 08:53
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Hi Rick,



Let me fix my  mistake.


Sorry for confusing you.


Here is correct info.


Seems yesterday i worked long hours.


U:\>tracert 172.21.100.20

Tracing route to 172.21.100.20 over a maximum of 30 hops

  1     5 ms    14 ms     6 ms  172.31.22.254----------IP of SW1 at site 1
  2    <1 ms    <1 ms    <1 ms  172.31.250.19---------IP of SW2 at site 1
  3    67 ms    67 ms    68 ms  172.21.100.20--------------------------IP of Router 2 Site 3


Seems this is correct behaviour of traceroute now right?


Regards


Mahesh

mahesh18 Sat, 02/22/2014 - 11:44
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MAny thanks Rick for providing your inputs into this.


Best Regards

Mahesh

mahesh18 Sat, 02/22/2014 - 08:49
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Hi Reza,


172.21.100.20 is IP of R2


Regards


Mahesh

Correct Answer
Richard Burts Sat, 02/22/2014 - 08:55
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Mahesh


What about this line from your original post

3    67 ms    67 ms    68 ms  172.21.100.20-------------------------IP of SW1 at sie 2


HTH


Rick


[edit] I think it would help if you would give us the diagram of this again and put IP addresses in the diagram for each of the device interfaces.

Also I realize that I have been assuming that the switches that you mention were operating as layer 3 routing devices. If the switch connected to R2 is actually a layer 2 switch then what you are seeing might be the correct behavior. So some more information about how things are configured would be helpful.

mahesh18 Sat, 02/22/2014 - 09:00
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Seems that was mistake Rick.

I should have typed there Site 3 ----Router2.


That was typo


Regards


Mahesh

Correct Answer
Reza Sharifi Sat, 02/22/2014 - 10:16
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  • Super Bronze, 10000 points or more
  • Cisco Designated VIP,

    2017 LAN

Hi Mahesh,



So you have a tunnel-1 (router) to tunnel-2 (router) to tunnel-3 (router)?

Are the end points for each tunnel a router?

Can you add IPs to your diagram?

It maybe you enter tunnel-1 and then right into the second tunnel and out

can you clarify?


Reza

mahesh18 Sat, 02/22/2014 - 11:36
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Hi REza,


End points of tunnels are routers

Yes i enter tunnel 1 then right into tunnel 2 that correct.


I put the ips to diagram in original post.


Regards


MAhesh

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