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Re: tcpdump for LVS

To: "LinuxVirtualServer.org users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: tcpdump for LVS
From: Horms <horms@xxxxxxxxxxxx>
Date: Wed, 28 Sep 2005 10:40:29 +0900
On Tue, Sep 27, 2005 at 11:49:29AM -0400, Jacob Coby wrote:
> Is there anything special I need to do to get tcpdump to work with LVS 
> in DR mode?  I've been trying to chase down this problem I've been 
> having with connections being opened, but never closed, and I want to 
> make sure I'm capturing the best data possible.
> 
> Right now, I'm doing tcpdump "port 80 and ether dst [director mac] and 
> src host [offending ip]".  If I don't include the director's mac 
> restriction, it logs the duplicate (resent) packets to the real server.
> 
> So far, I've found:
> 
> - Most connections are 5-packets long that send small amounts of data 
> (~600 bytes) (seems normal for a website)
> - Several RESET packets.
> - the idletime max from tcptrace seems very, very high: idletime max: 
>    328238.1 ms.  I've seen it over 2 million ms.
> 
> If someone would be willing to help, I have tcpdumps and tcptrace 
> outputs that include the problem connections along with normal 
> connection data.  I just don't know how to analyze it.

You shouldn't need to do anything special, though having
tcpdump log the mac address can help differentiate between
packets for the VIP received by the linux-director, and packets
for the VIP sent from the linux-director to real-servers.

-- 
Horms

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