Problem with postfix when setting up a loopback interface for load balancing

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Problem with postfix when setting up a loopback interface for load balancing

Adam Mason
I have some mail servers running postfix on FreeBSD that I am trying to configure to work with a load balancer.  I need to configure the lo0 loopback interface to use the IP address the load balancer will be handling for this group of mail servers.  Also I need to turn off ARP on the interface to keep the servers being load balanced from telling the switch to associate the balanced IP address with their own MAC addresses.

Currently I'm running the following command, and it seems to work well for another set of postfix servers that use different postfix configurations:

ifconfig lo0 1.2.3.4 netmask 255.255.0.0 -arp up

(1.2.3.4 being whatever the IP address the load balancer is managing for the group of servers)

The first group of servers I tried this on seemed to work fine, but when I tried this on another server I started getting a large number of error messages like the following:

Sep 29 10:45:38 {hostname} postfix/smtpd[39862]: warning: problem talking to server 127.0.0.1:10023: Permission denied

It looks like postfix is attempting to communicate with postgrey running on port 10023, but is unable to connect for some reason.  The servers that I have successfully setup to use load balancing aren't using postgrey, which is probably why I haven't run into this connection issue yet with them.

I'm still fairly new to postfix, unix, and networking, so any help / direction would be greatly appreciated.

- A.M.
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Re: Problem with postfix when setting up a loopback interface for load balancing

Wietse Venema
Adam Mason:
> Sep 29 10:45:38 {hostname} postfix/smtpd[39862]: warning: problem talking to
> server 127.0.0.1:10023: Permission denied

If you configure lo0 to be something other than 127.0.0.1,
then what interface listens on the 127.0.0.1 address?

        Wietse