Re: about iperf
One thought -- this sounds like a classic MTU black hole. The
negotiations are done with small packets, but when the first big packet
goes out, it is dropped and the connection hangs. Maybe a VLAN or
something wasn't set up properly. Is the MTU the same for all servers?
You could test this by having a ssh connection from c to b (or b to c),
and then try to cat or otherwise print a large file to the terminal. If
it's an MTU black hole (and TCP for ssh negotiates the same MSS as with
iperf I suppose), that connection will also hang.
It could also be some security/firewall thing, too. You could also try
a tcpdump on either side, and see what is going on.
--Matt
On 8/14/2006 11:37 PM, Bob wrote:
> Hi, all,
>
> I am currently testing a link. I have 3 servers located in three points separately. The 3 servers are all running linux OS.
>
> The topology looks like this:
>
>
>
> Point1 Point2 Point3
>
> A-------------------------------------------------------ï
>
> ---------------------------------------------C
>
> B__â
>
> I can traceroute between A-B, B-C, A-C successfully. And I can run iperf between A-B, A-C.
>
> But when I ran iperf between B-C, no matter I configure B as server or client, iperf will halt after connection is built. I donât know what the reason is. It seems that network connections between the three points are ok. Could this problem be caused by security configuration?
>
> Have you ever met such problem? Please give me some suggestions.
>
> Thanks.
>
> Bob