[Linux-cluster] Ip Settings

Stewart Walters stewart at epits.com.au
Fri Jan 23 02:40:44 UTC 2009

burton at simondsfamily.com wrote:
> I would like some advice on setting up a High  Availability solution using RHCS with Apache.
> I would like my clustered nodes to communicate on vlan, and the client connections to come through another vlan.   Presently, I have 2 interfaces on each of 2 nodes.  1 interface on each vlan.  I also have a vip address for the clients to connect to for the apache server.
> node a:
> xxx.xxx.100.1  eth0 (used for client connections)
> xxx.xxx.200.1  eth1 (used for interconnect, cluster communication)
> node b
> xxx.xxx.100.2  eth0 (used for client connections)
> xxx.xxx.200.2  eth1 (used for interconnect, cluster communication)
> xxx.xxx.100.100 address for clients to connect to apache.
> My question is how do I configure the apache service (and / or the resources)  to use client interfaces using the vip address?
> If i need to provide more information, please ask.  This is my first go at setting up a cluster.
> Thank you,
> B
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> Linux-cluster at redhat.com
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One way to do this is similar to a way that I have done on previous 
customer.  We had several different NICs each with a VLANed IP and we 
used differing DNS names attached to each NIC to allow the traffic to be 
routed via particular NICs.

So you might want the following in DNS:

nodea.example.com = xxx.xxx.100.1
nodea-cluster.example.com = xxx.xxx.200.1
nodeb.example.com = xxx.xxx.100.2
nodeb-cluster.example.com = xxx.xxx.200.2

In the previous installation, we had to also put in place some advanced 
IP routing policies through the iproute2 package.  The trick is to send 
any traffic received on the eth1 that back out via eth1 - not via the 
default route (which would be eth0).

Linux Journal has an article on how to do this titled "Overcoming 
Asymmetric Routing on Multi-Homed Servers" found at 

Then you just define in your cluster.conf that the two nodes are 
nodea-cluster.example.com and nodeb-cluster.example.com instead of 
nodea.example.com etc. etc.

We ran in to our fair share of network traffic problems with this sort 
of configuration due to the complexity of the network we were working 
with but once we had tuned it, it worked quite well.

If you can, I'd recommend you make yourself friendly with top-gun 
network engineer to help you assist you with networking issues should 
they arise. They can be invaluable when troubleshooting something that 
doesn't work :-)



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