Upstream Provider Woes? Point the Ping of Blame - page 4

Network Admin's Best Tool

Another good tool is plain old traceroute. Remote traceroutes are especially interesting. Find these at traceroute.org.

This is good for showing recalcitrant support techs that the problem really is theirs, and not something you are doing, because you can show traceroutes originating from different locations. I know, the old support-by-consensus is lame--"but ma'am, no one else is reporting a problem!" But we often must deal with it.

A side note on traceroute.org--a lot of the links are no longer valid, so it would be nice to politely inform them of any dead links you find.

Another thing traceroute is good for is to have your service provider run it from their end back to you. Sometimes the return path contains problems, so this is an important step. Especially if they are being fussy about admitting there is a problem.

Ole ping is still useful for network testing. Suppose that mtr shows that your ISP is dropping packets like they were toxic waste--ping the offending host and collect some nice statistics:

$ ping ortelco.net

PING ortelco.net (12.169.174.3): 56 data bytes
64 bytes from 12.169.174.3: icmp_seq=0 ttl=63 time=41.0 ms
64 bytes from 12.169.174.3: icmp_seq=3 ttl=63 time=1740.2 ms

64 bytes from 12.169.174.3: icmp_seq=4 ttl=63 time=2289.4 ms
64 bytes from 12.169.174.3: icmp_seq=5 ttl=63 time=1971.1 ms
....

--- ortelco.net ping statistics ---
100 packets transmitted, 34 packets received, 66% packet loss
round-trip min/avg/max = 41.0/1510.4/2289.4 ms

The interesting bits here are the dropped packets and the horrendous ping times. Anything under 100 milliseconds is good. At 150 milliseconds, you'll notice slower-loading Web pages, and possibly mail and Web timeouts. So anything in the thousands is obviously unworkable.

When you contact your service provider, don't try to attempt a diagnosis. Just show them the statistics you have collected. There are all kinds of things going on behind the scenes that ping, mtr, and traceroute cannot show you. All you want to do is show proof of a problem--it's up to them to diagnose and fix it.