Adding a Load Balancer in the DMZ

If the DMZ load balancer meets the prerequisite requirement and the firewalls are configured properly, enable the load balancer to support APNS by adding entries in the SAP Mobile Platform Server's host file.

Prerequisites

The DMZ load balancer must:

Be able to handle SSL connections and pass the client certificate through to the APNS server upon challenge.
Have firewall rules that allow connection to the APNS server farm. Because APNS uses a load-balancing scheme that results in different IP addresses at different times for the same host name, Apple recommends that you specify the entire 17.0.0.0/8 address block in your firewall rules. See https://developer.apple.com/library/ios/technotes/tn2265/_index.html#//apple_ref/doc/uid/DTS40010376-CH1-TNTAG41.

The steps below have been tested with the two load balancers listed below and should work for other load balancers. For more information on setting up the two load balancers tested, see:

Citrix Netscaler – http://support.citrix.com/proddocs/topic/netscaler-ssl-92/ns-ssl-bridging-tsk.html
F5 Big IP – http://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-11-1-0/15.html

Task

Log in with administrative privileges to the SAP Mobile Platform Server host machine.
Go to the directory where the hosts file is located:
- Windows – C:\Windows\System32\drivers\etc\
- Linux – /etc/
Back up the hosts file.
Use a text editor to open the hosts file.
Add these two lines to the end of the file, mapping IP addresses to the APNS:
```
XXX.XXX.XXX.XXX gateway.sandbox.push.apple.com
YYY.YYY.YYY.YYY feedback.sandbox.push.apple.com
```
where:
- XXX.XXX.XXX.XXX is the gateway push IP address of the load balancer virtual server (LBVS).
- YYY.YYY.YYY.YYY is the feedback push IP address of the LBVS.
Note: Inclusion of ".sandbox" in the domain names is for testing purposes. In a production installation, omit ".sandbox" from each domain name:
```
... gateway.push.apple.com
... feedback.push.apple.com
```
Save and close the file.

Now when SAP Mobile Platform Server sends a notification to a device via APNS, the underlying network layers resolve the host address using the hosts file, which references the load balancer.