Just a reminder on how to set separate static routes for interfaces in RHEL/CentOS.

[root@zaphod ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
NETWORK=192.168.200.0
NETMASK=255.255.252.0
IPADDR=192.168.200.1
USERCTL=no
HWADDR="00:00:00:00:00:00"
NM_CONTROLLED="yes"
TYPE="Ethernet"
UUID="redacted_string"

[root@zaphod ~]# cat /etc/sysconfig/network-scripts/route-eth0

192.168.0.0/16 via 192.168.200.7

[root@zaphod ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth1

DEVICE=eth1
BOOTPROTO=none
ONBOOT=yes
NETWORK=10.1.200.0
NETMASK=255.255.252.0
IPADDR=10.1.200.200
USERCTL=no
HWADDR="00:00:00:00:00:00"
NM_CONTROLLED="yes"
TYPE="Ethernet"

[root@zaphod ~]# cat /etc/sysconfig/network-scripts/route-eth1

10.200.2.0/24 via 10.1.200.254
10.31.255.0/24 via 10.1.200.254

[root@zaphod ~]# route

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.31.255.0     10.1.200.254    255.255.255.0   UG    0      0        0 eth1
10.200.2.0      10.1.200.254    255.255.255.0   UG    0      0        0 eth1
10.1.200.0      *               255.255.252.0   U     0      0        0 eth1
192.168.200.0   *               255.255.252.0   U     0      0        0 eth0
link-local      *               255.255.0.0     U     1002   0        0 eth0
link-local      *               255.255.0.0     U     1003   0        0 eth1
192.168.0.0     192.168.200.7   255.255.0.0     UG    0      0        0 eth0
default         192.168.200.7   0.0.0.0         UG    0      0        0 eth0

https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/s1-networkscripts-static-routes.html