[CentOS] Making FORWARD_IPV4=YES permanent / DHCP multiple routers

First,

I'd like to configure my system to forward ip, to act as a gateway for my network. I've always used a script during startup to do this:

echo 1 > /proc/sys/net/ipv4/ip_forward iptables -t nat -A POSTROUTING -o ${UPLINK} -j SNAT --to ${IP_NAT}

This works fine, however I want this permanent so I don't have to run the script on startup. I have the firewall setup with SNAT fine, but when I write the file /etc/sysconfig/network with the line 'FORWARD_IPV4=YES' it still doesn't enable the ip forwarding after boot?

cat /proc/sys/net/ipv4/ip_forward 0

So how do I do this?

Second, In DHCP, you can specify multiple DNS servers:

option domain-name-servers 10.0.0.1, 10.0.0.2, 10.0.0.3;

can you also do this with routers?

option routers 10.0.0.1 10.0.0.2;

so that if one is down, the network PC's can fail over to another?