[smokeping-users] best test to use?

Chris Wilson chris+smokeping at aptivate.org
Fri Nov 5 09:09:47 CET 2010

Hi Adam,

On Fri, 5 Nov 2010, Adam Hardy wrote:

> I have a problem with some software running on a windows machine on the 
> LAN where the company who wrote the sofware say that there must be 
> something wrong with my internet connection, but can't help any further.
> I'd like to know what tests I can run to verify that my config and my 
> firewall are OK, especially regarding PMTU.
> I tried running without my firewall but it makes no difference so maybe 
> it's something else out there with my ISP before it hits the public net.

Simply running "without a firewall" is not enough to make it work. The 
firewall has to actively reverse NAT the ICMP Unreachable messages that it 
receives from the Internet for PMTU to work.

> What can I do with ping? This ping command gives suspicious results:
>  ping -s 1473 mktgw1.ibllc.com

You didn't tell us the results. You also didn't tell us what the actual 
problem is with the software.

I would forget about ping and run Wireshark or tcpdump on your firewall, 
capturing packets on both sides and comparing the differences. Look for a 
packet received on one side that's not forwarded correctly to the other, 
or look for the point where the conversation stops.

I would also consider trying a different Internet connection, e.g. a 3G 
dongle or a friend's DSL router/connection.

Cheers, Chris.
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