An example of using the Salt peer interface to query web server IP addresses and add them to an iptables config.

iptables

# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
{% for ipaddr in ipaddrs %}
-A INPUT -p tcp -s {{ ipaddr[0] }}  --sport 1024:65535 -d {{ dbserver }} --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT
-A OUTPUT -p tcp -s {{ dbserver }} --sport 3306 -d {{ ipaddr[0] }} --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT
{% endfor %}
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT

iptablesconfig.sls

/etc/sysconfig/iptables:
  file.managed:
    - source: salt://dbserver/iptables
    - user: root
    - group: root
    - mode: 600
    - template: jinja
    - dbserver: {{ salt['publish.publish']('dbserver', 'network.ip_addrs', 'eth1')['dbserver'].pop() }}
    - ipaddrs: {{ salt['publish.publish']('*web*', 'network.ip_addrs', 'eth1').values() }}

retr0h! Are you using saltstack these days?

OMG.. This example makes me want to cry..

THANK YOU.