Re: [lvs-users] ipvsadm and packets leaving a gre tunnel

To: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] ipvsadm and packets leaving a gre tunnel
From: "Marco Lorig" <MLORIG@xxxxxxx>
Date: Tue, 22 Jul 2008 16:49:41 +0200
On Tue, 22 Jul 2008, Joe wrote:

>Ratz's solution is on the director, and sets the MTU for the

I´ve to check this on our setup.

>not sure what you're doing here. Is it one connection with
>this route?

Both "directors" are connected via GRE. The first director starts routing to 
the second one through the tunnel as soon as the realservers behind it aren´t 
available anymore. So it "turns off" the ipvsadm and switches itself to a 
routing instance. The second director, which also serves clients and servers at 
its location by ipvsadm, starts another ipvsadm instance on the GRE interface 
and is receiving routed packets from the first director through GRE tunnel.


>I assume you have two directors in some standard failover
>setup and only one is directing when your LVS is up?

It isn´t a typical failover scenario. On each location are two machines 
The failover I´m talking about is switching between datacenters. 

If the realservers after director1 at location 1 aren´t available anymore, the 
director1 starts normal routing operation through tunnel to the other director2 
at location 2, which handles it´s own ipvsadm instances, clients and 
The director2 now serves client from location 1 with servers at location 2 
through GRE Tunnel.

>the copy has nothing to do with LVS? ie you can do the copy
>when there is nothing in the ipvsadm table in the 2nd
>(inactive) director, but as soon as you put entries into
>ipvsadm on the backup director, the gre tunnel breaks?

Making a connection from client n, location 1, to an address on director 1, the 
director1 routes the packets through the tunnel to location 2. Without running 
ipvsadm on director 2, location2, the connection establishes correctly and the 
a 600Kb file transfer works fine.

Starting ipvsadm on the gre interface of director2, location2, makes the file 
transfer hang due to mtu issues, I presume.

All instances on ipvsadm breaks the tunnel except if a client connects before 
to the realserver directly as is explained in the "update" email, I sent 

It´s strange but it think I´m getting closer.

Thanks for your help.


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