[CentOS] What on Centos is wiping out my eth0 IP address every 5 minutes?

Tue Jul 23 23:24:21 UTC 2013
Rock <Rocksockdoc at gmail.com>

On Tue, 23 Jul 2013 16:05:23 -0700, John R Pierce wrote:

> https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/ch-NetworkManager.html

That reference doesn't say much about what to set the gateway to:
 http://i41.tinypic.com/1z2n6uv.jpg

Reading section 8.3.9.4 "Configuring IPv4 Settings":
https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/sec-Configuring_Connection_Settings.html

All it says about the "Gateway" is:
  Gateway — The IP address of the gateway leading to the network, sub-net or host. 

In my situation, I'm connecting a CAT5 cable from the RJ45 eth0 port of the laptop
to a radio, which is a router, which is, by default, set up to *not* hand out 
DHCP addresses (Ubiquiti Nanobridge M2) and which is set up, by default, on IP 
address 192.168.1.20.

Given that information, do you have any idea what I should set the gateway to 
in the suggested forms? (they won't let me leave the gateway blank)