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James Fidell wrote: > >> traceroute uses ping, it might be that the 6th hop host is not >> responding to ping, I have seen this and assumed this was the issue. > > Traceroute does not use ping. > > ping sends an ICMP echo request packet to the target system, which > responds with the echo reply assuming it isn't firewalled or disabled > some other way. > > traceroute sends packets with increasing TTLs creating a "map" of the > path between the source and target by finding the host that bounces > the packet with a TTL exceeded error. AFAIR, the packets it sends are > udp packets addressed to random high-numbered ports. By default UDP, "-I" allows ICMP to be used with traceroute. If that is insufficient hping3 will probably do almost anything people need, if you can decipher the options. Since with hping3 you can use the protocol associated with the service of interest, it should get passed most firewalls, but asymetric routing can cause interesting issues. We tend to naively assume that packets come back the way they went, but that is because most of us don't have the tools to reveal when this isn't the case, as James knows judging from his answer. The secret is to traceroute from both ends with the protocol and ports in use, although I've seen situations where that didn't tell the whole story, but routing engineers have to have some uses ;) Funniest story on asymmetric routing, was after firewalling someone's network from the Internet, their ISDN line to the states immediately stopped working. It was then they discovered that the return route from the states was via their Internet connection (whoops).
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