Treceroute issue

[ITexpert]

Hello Guys,

My ping is working but trace-route works partially , please see attached picture.

Any suggestions will be helpful.

[michael.burke]

Traceroute uses UDP packets so sometimes even though ping is allowed traceroute may still be blocked.
This post is pretty good for some background.
https://learningnetwork.cisco.com/thread/87662

[balaji.bandi]

PING  command uses the services of the Internet Control Message Protocol (ICMP), the latter being encapsulated in the IP header. Therefore, the ping utility operates basically on layer 3 (the Network layer) of the OSI model. It does not use the services of the Transport layer, and the reason for that is that traffic reliability issues are not the case here. Ping performs a simple host lookup.

TRACEROUTE is another very helpful utility that operates similarly to ping and also uses the services of the ICMP protocol. Traceroute, as the name implies, is used to trace the path between the sender and the destination host.

In your case a couple of request timed out messages come from routers that are configured not to respond to ICMP echo request messages.

There is good old cisco document for reference, if you like to understand more :

https://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/ios-software-releases-121-mainline/12778-ping-traceroute.html

[Richard Burts]

BB seems to be quoting something that says that traceroute makes use of ICMP protocol. Depending on how you look at it this is not true. Some devices (for example Windows PCs) do use ICMP for the traceroute probe packets. But other devices (Cisco routers and switches for example) do not use ICMP for probes but use UDP.

The original post asks about some results of traceroute where the first several sets of probe packets did not receive any response and then a couple of probe packets did receive responses. It is possible that the devices at the first several hops were denying the probe packets or it is possible that these devices are configured to not respond with TTL expired. 

Does the original poster still have questions about this?

HTH

Rick

[Vishnu Vardhan S]

Hi !!

From the tracerout output I understood that we are using MPLS in the network, normally we have to enable a know in MPLS configuration to see the device IP, in our case I think that is missing because of which you are seeing * in traceroutes.