dual stack binding

[abatie]

I have nginx binding to a variety of addresses for ssl and target selection
reasons.  Now I'm trying to add ipv6 support.  Since I'm using specific
listen addresses, I wouldn't expect to have a binding conflict, however I
am, and I'm hoping someone can point me in the right direction:

    server {
	listen 207.55.17.79:25;
...
    server {
	listen [2607:f678::17:79]:25;
...

<mailproxy-lb-01.peak.org> [150] # service nginx restart
Stopping nginx:                                            [FAILED]
Starting nginx: nginx: [emerg] bind() to [2607:f678::17:79]:25 failed (99:
Cannot assign requested address)
                                                           [FAILED]

The local mail server is only listening on localhost:

tcp        0      0 ::1:25                      :::*                       
LISTEN      

Commenting out the smtp server config just moves the conflict to the next
port in question...

nginx/1.7.6
CentOS release 6.9 (Final)

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,280234,280234#msg-280234