[Linux-cluster] LVS: Not as a gateway?

Mon Nov 6 03:29:40 UTC 2006

Hi Chris,

I'm still not getting this. Same problem, all weekend.

Nov  5 21:28:46 lb52 nanny[1227]: READ to 192.168.1.94:80 timed out
Nov  5 21:28:46 lb52 nanny[1226]: READ to 192.168.1.93:80 timed out
Nov  5 21:28:46 lb52 nanny[1225]: READ to 192.168.1.92:80 timed out
Nov  5 21:28:58 lb52 nanny[1227]: READ to 192.168.1.94:80 timed out
Nov  5 21:28:58 lb52 nanny[1226]: READ to 192.168.1.93:80 timed out
Nov  5 21:28:58 lb52 nanny[1225]: READ to 192.168.1.92:80 timed out

> accept packets with that address. However, they do not respond to ARP
> requests, therefore that IP can exist on all servers in this cluster and not
> cause communication problems. Ie., if you were to ping that address, only
> the director would respond. I have configured real servers before with just
> these three lines of code:

I understand the concept, it's just not working for me, so far. I'm missing 
something for sure.

> ifconfig lo:1 $VIP netmask 255.255.255.255 up

I have the VIP set up on my first NIC on a real server.
  eth0:1 	Ethernet (Virtual) 	192.168.1.150 	255.255.255.0 	Up

I have 192.168.1.150 installed on LVS0 as the VIP for the real servers and 
real servers configured.

> echo 1 > /proc/sys/net/ipv4/conf/all/hidden
> echo 1 > /proc/sys/net/ipv4/conf/lo/hidden

These files do not exist on RHEL4 so cannot do this.

> That's it. If a real server can accept packets addressed to the virtual IP
> and does not respond to ARP on that IP, it's done, all set up. If nanny
> requires more, then maybe there is more, but that's the guts of the LVS
> stuff on real servers.

Ok, so there's my problem, where I'm misunderstanding something here.
The LVS servers respond to my VIP of 192.168.1.150 and the real servers have 
that IP as a virtual IP but they don't respond. 

I think I'm not understanding something with the floating and virtual IP's. 
They are the same correct? Client connects to VIP on the LVS and LVS sends 
connection to one of the real servers which all know to use the same virtual 
IP?

Mike

> The LVS director (and it's partner if there are two directors) accept all
> packets that are sent to the floating IP, whether they get there by NAT
> through a firewall, or directly from a machine on the same network, or
> anywhere else. Say I want a web page from this cluster. I send an http
> request to your floating IP. The director gets it, chooses a real server,
> and then forwards the packet there. The real server serves the request and
> replies directly to the client, using the virtual IP as the source in the
> packet header, such that client never realizes that it dealt with more than
> one machine. From the client side, it sent an http request to your virtual
> IP (hypothetically) 10.10.10.9 which got accepted by the director and it got
> a packet back from 10.10.10.9 (which is bound to the loopback on the real
> server, so it can use that address as its source). And voila, a transparent
> load balanced cluster. I can't answer a redhat specific question because I
> don't know the answer, but maybe this will help you diagnose what is not
> working.
> 
> Chris
> 
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> Linux-cluster at redhat.com
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On Thu, 2 Nov 2006 16:52:56 -0500, Christopher Hawkins wrote:
>> -----Original Message-----
>> 
>> From: linux-cluster-bounces at redhat.com
>> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of
>> isplist at logicore.net
>> Sent: Thursday, November 02, 2006 3:51 PM
>> To: linux-cluster
>> Subject: RE: [Linux-cluster] LVS: Not as a gateway?
>> 
>> Maybe someone who's running DIRECT and all of the same
>> internap IP's. can send me their lvs.cfg? I'm stumped.
>> 
>> Yes, it's how I've got it set up. Only problem is, the web servers need to
> see the LVS as their gateways no?
> 
> No. I'm not familiar with the redhat way of doing this, but I know LVS. So
> if I trample on accepted redhat wisdom someone please correct me.... But
> straight, cross-platform LVS works like this: The real servers do not even
> need to know they are part of an LVS cluster. They can be setup like any
> typical server providing a service, like httpd or whatever, and then they
> get the virtual IP bound to their loopback interface so that they will
> accept packets with that address. However, they do not respond to ARP
> requests, therefore that IP can exist on all servers in this cluster and not
> cause communication problems. Ie., if you were to ping that address, only
> the director would respond. I have configured real servers before with just
> these three lines of code:
> ifconfig lo:1 $VIP netmask 255.255.255.255 up
> echo 1 > /proc/sys/net/ipv4/conf/all/hidden
> echo 1 > /proc/sys/net/ipv4/conf/lo/hidden
> 
> That's it. If a real server can accept packets addressed to the virtual IP
> and does not respond to ARP on that IP, it's done, all set up. If nanny
> requires more, then maybe there is more, but that's the guts of the LVS
> stuff on real servers.
> 
> The LVS director (and it's partner if there are two directors) accept all
> packets that are sent to the floating IP, whether they get there by NAT
> through a firewall, or directly from a machine on the same network, or
> anywhere else. Say I want a web page from this cluster. I send an http
> request to your floating IP. The director gets it, chooses a real server,
> and then forwards the packet there. The real server serves the request and
> replies directly to the client, using the virtual IP as the source in the
> packet header, such that client never realizes that it dealt with more than
> one machine. From the client side, it sent an http request to your virtual
> IP (hypothetically) 10.10.10.9 which got accepted by the director and it got
> a packet back from 10.10.10.9 (which is bound to the loopback on the real
> server, so it can use that address as its source). And voila, a transparent
> load balanced cluster. I can't answer a redhat specific question because I
> don't know the answer, but maybe this will help you diagnose what is not
> working.
> 
> Chris
> 
> --
> Linux-cluster mailing list
> Linux-cluster at redhat.com
> https://www.redhat.com/mailman/listinfo/linux-cluster