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[lvs-users] Real Servers receive nothing

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char.hon at iptech

May 25, 2009, 11:04 PM

Post #1 of 6 (1003 views)
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[lvs-users] Real Servers receive nothing

Hello,

I am trying to configure LVS on CentOS 5.3.
I have followed the tuturial LVS-NAT on
http://www.ultramonkey.org/papers/lvs_tutorial/html/

I have typed on the load balancer :
ifconfig eth0:0 10.8.8.85 netmask 255.255.255.0
ipvsadm -A -t 10.8.8.85:80
ipvsadm -a -t 10.8.8.85:80 -r 10.8.10.2:80 -m
ipvsadm -a -t 10.8.8.85:80 -r 10.8.10.3:80 -m

the ip forwarding is correctlt activated.

The network mask for every ip is 255.255.255.0.

Virtual IP = 10.8.8.85

|-------|-------------------------
|eth0=10.8.9.1
|
------|----------
| loadbalancer |
| router |
| |
------|----------
|eth1=10.8.10.1
|
|-------|-|------------------|-------------------
|eth0=10.8.10.2 |eth0=10.8.10.3
|gateway=10.8.8.85 |gateway=10.8.8.85
|---------| |---------|
| rs1 | | rs2 |
|_________| |_________|

It does not work and I don't have any ideas how to debug that.

Thank you very much for your help.

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graeme at graemef

May 25, 2009, 11:59 PM

Post #2 of 6 (961 views)
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Re: [lvs-users] Real Servers receive nothing [In reply to]

On Tue, 2009-05-26 at 14:04 +0800, Guillaume Charhon wrote:
> It does not work and I don't have any ideas how to debug that.

The default gateway for the realservers should be 10.8.10.1.

If the netmask for everything is 255.255.255.0 (/24) then they'll have
no idea how to route back to 10.8.8.85.

Graeme

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char.hon at iptech

May 26, 2009, 1:48 AM

Post #3 of 6 (966 views)
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Re: [lvs-users] Real Servers receive nothing [In reply to]

Hello,

Ok, but the packets does not seems to go to the realservers. There is no log
entry in apache. So the gateway is not the main problem.

Thank you.

Graeme Fowler wrote:
>
> On Tue, 2009-05-26 at 14:04 +0800, Guillaume Charhon wrote:
>> It does not work and I don't have any ideas how to debug that.
>
> The default gateway for the realservers should be 10.8.10.1.
>
> If the netmask for everything is 255.255.255.0 (/24) then they'll have
> no idea how to route back to 10.8.8.85.
>
> Graeme
>
>
> _______________________________________________
> Please read the documentation before posting - it's available at:
> http://www.linuxvirtualserver.org/
>
> LinuxVirtualServer.org mailing list - lvs-users [at] LinuxVirtualServer
> Send requests to lvs-users-request [at] LinuxVirtualServer
> or go to http://lists.graemef.net/mailman/listinfo/lvs-users
>
>

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thomas at pedoussaut

May 26, 2009, 3:30 AM

Post #4 of 6 (961 views)
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Re: [lvs-users] Real Servers receive nothing [In reply to]

poiuytrez wrote:
> Hello,
>
> Ok, but the packets does not seems to go to the realservers. There is no log
> entry in apache. So the gateway is not the main problem.
>
>
IP 101 is your friend. I mean, SYN packets probably reach the RS, but
because the ACK arrive out of context on the client, the TCP connection
is never fully established, even less the HTTP connection, hence no
entries in your apache logs. You can probably confirm my theory in
running tcpdump on the RS, and you'll see the SYN packets arriving.

--
Thomas

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char.hon at iptech

May 26, 2009, 7:09 PM

Post #5 of 6 (948 views)
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Re: [lvs-users] Real Servers receive nothing [In reply to]

I have tried the tcp dump but it gives to much info, I don't really
understand it, but it does not seems to have any http request.
Here is a screen shoot at time of the request. The workstation that tries to
retrive the page is 10.8.8.111.
http://www.nabble.com/file/p23734830/screen.jpg

Thank you.

Thomas Pedoussaut-2 wrote:
>
> poiuytrez wrote:
>> Hello,
>>
>> Ok, but the packets does not seems to go to the realservers. There is no
>> log
>> entry in apache. So the gateway is not the main problem.
>>
>>
> IP 101 is your friend. I mean, SYN packets probably reach the RS, but
> because the ACK arrive out of context on the client, the TCP connection
> is never fully established, even less the HTTP connection, hence no
> entries in your apache logs. You can probably confirm my theory in
> running tcpdump on the RS, and you'll see the SYN packets arriving.
>
> --
> Thomas
>
> _______________________________________________
> Please read the documentation before posting - it's available at:
> http://www.linuxvirtualserver.org/
>
> LinuxVirtualServer.org mailing list - lvs-users [at] LinuxVirtualServer
> Send requests to lvs-users-request [at] LinuxVirtualServer
> or go to http://lists.graemef.net/mailman/listinfo/lvs-users
>
>

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_______________________________________________
Please read the documentation before posting - it's available at:
http://www.linuxvirtualserver.org/

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Send requests to lvs-users-request [at] LinuxVirtualServer
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char.hon at iptech

May 26, 2009, 7:38 PM

Post #6 of 6 (947 views)
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Re: [lvs-users] Real Servers receive nothing [In reply to]

I have inverstigated deeper with filtering only the port 80. Packets now go
to

The request is going to the real server, then go back to the load balancer
but never go back to the workstation. No output on eth0 to go out... (only
10.8.8.111 > 10.8.8.85)
Do I have to add a route or something like that ?

Thank you.

poiuytrez wrote:
>
> I have tried the tcp dump but it gives to much info, I don't really
> understand it, but it does not seems to have any http request.
> Here is a screen shoot at time of the request. The workstation that tries
> to retrive the page is 10.8.8.111.
> http://www.nabble.com/file/p23734830/screen.jpg
>
> Thank you.
>
>
>
>
> Thomas Pedoussaut-2 wrote:
>>
>> poiuytrez wrote:
>>> Hello,
>>>
>>> Ok, but the packets does not seems to go to the realservers. There is no
>>> log
>>> entry in apache. So the gateway is not the main problem.
>>>
>>>
>> IP 101 is your friend. I mean, SYN packets probably reach the RS, but
>> because the ACK arrive out of context on the client, the TCP connection
>> is never fully established, even less the HTTP connection, hence no
>> entries in your apache logs. You can probably confirm my theory in
>> running tcpdump on the RS, and you'll see the SYN packets arriving.
>>
>> --
>> Thomas
>>
>> _______________________________________________
>> Please read the documentation before posting - it's available at:
>> http://www.linuxvirtualserver.org/
>>
>> LinuxVirtualServer.org mailing list - lvs-users [at] LinuxVirtualServer
>> Send requests to lvs-users-request [at] LinuxVirtualServer
>> or go to http://lists.graemef.net/mailman/listinfo/lvs-users
>>
>>
>
>

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_______________________________________________
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