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how to hide the TRACE HOPS in the traceroute command

sivakondalarao
Level 1
Level 1

while doing trace we are not able to see few hops in the middle ; ( ie hops inside the cloud ) ; we want to know what command used for this ?

15 Replies 15

paolo bevilacqua
Hall of Fame
Hall of Fame

That happens when the ICMP time-exceeded messages cannot reach the station doing traceroute. It can happen intentionally using ACL, or as a byproduct of firewall or other policy. So if you configure an ACL blocking ICMP, (all or certain message types), you will achieve that.

Hope this helps, please rate post if it does!

I like it!

mohammedmahmoud
Level 11
Level 11

Hi,

If this is an MPLS cloud, then this can be accomplished via disabling the TTL propagation:

http://www.cisco.com/en/US/tech/tk436/tk428/technologies_tech_note09186a008020a42a.shtml#no_mpls

HTH,

Mohammed Mahmoud.

THANKS FOR YOUR UPDATE THIS IS THE THING WHAT WE REQUIRED EXACTLY

hi siva

For the SP from the Customer perspective this will be benefitical coz you will be reducing the intermediate hops and say the customer can reach the destination with less hops in between but as far Operations/Maintanence team is concerned it will be really difficult for them during troubleshooting process...

regs

Hi,

Totally agree with Edwin, and thats why for SP its recommended to use this command in the form "no tag-switching ip propagate-ttl forwarded" in order only for the command to take effect when the trace is done from the customer router and to be of no effect if the trace is done on the provider router.

HTH,

Mohammed Mahmoud.

hi all; thanks for your inputs; now i want to know how to crack this because in our mpls cloud for troubleshooting we need to see the hops....

Hi Sivakondalarao,

In order for this command to only affect your customers and not your self while troubleshooting use this form of the command "no tag-switching ip propagate-ttl forwarded".

HTH,

Mohammed Mahmoud.

Hi Mohammed,

I read this nice article already, but I'm still looking for another question answer:

15 172.30.211.3 [AS 65002] 588 msec 552 msec 552 msec

Where does this [AS number] in the traceroute output come from?

And why it's sometimes incorrect?

Thanks,

Milan

Hi Milan,

The traceroute resolves the autonomous system in the BGP table (The AS that this specific ip originated from) and thus the local router must be running BGP and each hop must have an entry in the BGP table, and thus for example a BGP router that only receive a default route from its upstream peer would put the AS of this peer in all the hops, inconsistency in the output may be a result to the availability of the route in the BGP table or may be due to aggregation issues where AS information is lost.

HTH,

Mohammed Mahmoud.

Hi Mohammed,

that explains some inconsistencies I found in the traceroute output.

Is this explanation your personal experience or have you found it described somewhere on CCO, e.g.?

Thakns a lot,

Milan

Hi Milan,

Actually, this was my personal experience, but i think we can find some doc to prove my theory.

BR,

Mohammed Mahmoud.

is there any way to crack this or how to see the hops in the MPLS cloud also;

i heard that some way of cracking this is avilable!!!!!!!!

Hi Sivakondalarao,

Yes, this is what i've been trying to tell you, if we use the command in its default form "no tag-switching ip propagate-ttl", this would hide the hops both for you and your customers, but in order for this command to only affect your customers and not your MPLS cloud while troubleshooting use this form of the command "no tag-switching ip propagate-ttl forwarded".

I hope that i've been informative, please don't hesitate if you have further questions.

HTH,

Mohammed Mahmoud.

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