[CentOS] Two Instances of Apache; Primary IP / Secondary IP

Tue Jan 29 00:38:09 UTC 2008
Al Sparks <data345 at yahoo.com>

> do you mean making apache use a specific IP when it proxies the request?
> (you really lost me, so I may be misunderstanding). why do need that at
> all? whatever IP is used should not matter since the backend will reply
> over the socket that was opened by the proxy (be it a production proxy
> or the test proxy).
> 

Both IP addresses are actually assigned to the same physical interface
(eth1 and eth1:1).  The proxy instance is accepting connections from
clients using the eth1:1 secondary interface, but the same PHYSICAL
interface as eth1.  When it turns around and connects to the back-end
service, it seems to be using eth1 even though it's listening on
eth1:1.  Since it's not listening to eth1, the packets are going to
the bit-bucket.  At least that's my theory.

> otherwise, the IP is selected by the kernel depending on the
> destination. so if you use something like
> ProxyPass / http://10.1.2.3:8080/
> in one proxy and
> ProxyPass / http://10.4.5.6:8080/
> 
> each will use the "selected" IP.
> 
>> Is there something I can do with routing tables that can help?
>>
> That would require "advanced" routing. standard routing is based on
> destination and the source IP is selected by the kernel after the route
> has been computed (this allows setting the right IP should you have
> multiple network interfaces...).
> 
> but you should not need this.

In the end, I may just have to either use a separate server or a
second physical interface, probably in another VLAN, to make this
work.  And my idea seemed like such a good one.
    === Al