I am toying with trace route, my application send a ICMP echo request with a ttl of 0 every time i receive a time exceeded message i increment the ttl by one and resent the package, but what happens is I have 2 routers on my network i can trace the route through these router but third hop always ends up being one of the open dns servers same ip every time no matter where i traceroute to. AFAIK this is the correct traceroute implementation, can anyone tell me what i am doing wrong?
+1
A:
It's possible that both routers connect to the same peer, and you'd get the described behaviour.
Without more info, it's not really possible to answer your question.
Frank Shearar
2010-03-31 12:13:15
"routers connect to the same peer" can you explain what you meant by that?
Hamza Yerlikaya
2010-03-31 13:20:03
I mean that there's nothing particularly strange about your two routers routing to the same machine.
Frank Shearar
2010-03-31 13:53:46
A:
While it's hard to say without any additional information, the best bet would be to install some packet sniffer — probably wireshark / www.wireshark.org — and compare the icmp packets — what goes on the wire with your traceroute, and what does the system /usr/bin/traceroute (or \windows\system32\tracert) send.
Einar Lielmanis
2010-03-31 12:22:22
A:
If you have a NAT router on the path it can screw up your nicely adjusted TTL's
joveha
2010-03-31 14:58:26
i have two routers on the path one is mine which i use inside the room the other belongs to the building i'm living in which very much like to mess with my connection, but regular traceroute works fine in this situation.
Hamza Yerlikaya
2010-03-31 15:08:32
I see. This "open dns server", is that also a router "in the building" or somewhere close? Have you tried using the regular traceroute command (with ICMP and UDP) to see if the result differ? Without more information I would conclude that the third router, which also acts as DNS, is blocking your packets - possibly because it's also NAT'ing.
joveha
2010-03-31 16:04:14
Are you saying that if you use the traceroute command it works, but your app that is mimicking traceroute doesn't? Seeing code might help us help you.
dbasnett
2010-04-05 21:46:40