Re: Something sick with traceroute6
On Wed, Apr 05, 2000 at 07:54:13PM +1000, Craig Small wrote:
> G'day,
> Something wierd with traceroute6
> scooter$ ping6 ftp.ipv6.nl
> PING ftp.ipv6.nl(ipv6.nl) 56 data bytes
> 64 bytes from ipv6.nl: icmp_seq=0 time=777.7 ms
> 64 bytes from ipv6.nl: icmp_seq=1 time=798.6 ms
>
> scooter$ traceroute6 ftp.ipv6.nl
> (lots of stars)
>
> What's going on here?
Traceroute works by sending udp packets to high numbered ports with an
incrementing ttl, and uses the icmp time-exceeded messages to determine hops,
and port-unreachable messages to determine when it has reached the destination.
It also sends icmp echo-requests (pings) to give you the usual ping results
for each hop.
As you can probably imagine, firewalling can play nasty games with
traceroutes, such as blocking your packets, not repsonding to pings, or even
not decrementing the ttl when forwarding high-numbered udp packets.
If I have any facts wrong here, corrections are welcomed, but that should give
you enough background to figure out where the problem is.
--
-- Michael Samuel <michael@sal.mik.hyperlink.net.au>
If A equals success, then the formula is A = X + Y + Z. X is work. Y
is play. Z is keep your mouth shut.
-- Albert Einstein
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