Take a look at /etc/rc.d/rc.local. The file states, "Please note that you must run 'chmod +x /etc/rc.d/rc.local' to ensure that this script will be executed during boot." So...

chmod +x /etc/rc.d/rc.local 

Then place your commands above the last line, touch /var/lock/subsys/local.

/etc/iproute2/rt_tables /etc/sysconfig/network /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth1 /etc/sysconfig/network-scripts/route-eth0 /etc/sysconfig/network-scripts/route-eth1 /etc/sysconfig/network-scripts/rule-eth0 /etc/sysconfig/network-scripts/rule-eth1 

# # reserved values # 255 local 254 main 253 default 0 unspec # # local # 128 mynet 

NETWORKING=yes HOSTNAME=hostname.sld.tld GATEWAY=10.10.10.1 

THE EL 7.x /etc/sysconfig/network-scripts/ifcfg-eth0 file, without "HWADDR" and "UUID". This configures a static IP address for eth0 without using NetworkManager.

DEVICE=eth0 TYPE=Ethernet ONBOOT=yes NM_CONTROLLED=no BOOTPROTOCOL=none IPADDR=10.10.10.140 NETMASK=255.255.255.0 NETWORK=10.10.10.0 BROADCAST=10.10.10.255 

THE EL 7.x /etc/sysconfig/network-scripts/ifcfg-eth1 file, without "HWADDR" and "UUID". This configures a static IP address for eth1 without using NetworkManager.

192.168.100.0/24 dev eth1 table mynet default via 192.168.100.1 dev eth1 table mynet 

from 192.168.100.0/24 lookup mynet 

dnf install network-scripts 

Take a look at /etc/rc.d/rc.local. The file states

Please note that you must run chmod +x /etc/rc.d/rc.local to ensure that this script will be executed during boot.

So:

chmod +x /etc/rc.d/rc.local 

Then place your commands above the last line

touch /var/lock/subsys/local 

/etc/iproute2/rt_tables /etc/sysconfig/network /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth1 /etc/sysconfig/network-scripts/route-eth0 /etc/sysconfig/network-scripts/route-eth1 /etc/sysconfig/network-scripts/rule-eth0 /etc/sysconfig/network-scripts/rule-eth1 

# # reserved values # 255 local 254 main 253 default 0 unspec # # local # 128 mynet 

NETWORKING=yes HOSTNAME=hostname.sld.tld GATEWAY=10.10.10.1 

THE EL 7.x /etc/sysconfig/network-scripts/ifcfg-eth0 file, without HWADDR and "UUID". This configures a static IP address for eth0 without using NetworkManager.

DEVICE=eth0 TYPE=Ethernet ONBOOT=yes NM_CONTROLLED=no BOOTPROTOCOL=none IPADDR=10.10.10.140 NETMASK=255.255.255.0 NETWORK=10.10.10.0 BROADCAST=10.10.10.255 

THE EL 7.x /etc/sysconfig/network-scripts/ifcfg-eth1 file, without HWADDR and UUID. This configures a static IP address for eth1 without using NetworkManager.

192.168.100.0/24 dev eth1 table mynet default via 192.168.100.1 dev eth1 table mynet 

from 192.168.100.0/24 lookup mynet 

dnf install network-scripts 

Update for RHEL8

This method described above works with RHEL 6 & RHEL 7 as well as the derivatives, but for RHEL 8 and derivatives, one must first install network-scripts to use the method described above.

dnf install network-scripts 

The installation produces a warning that network-scripts will be removed in one of the next major releases of RHEL and that NetworkManager provides ifup/ifdown scripts as well.