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)