Linux: Add routing from different class network A (192.168.1.x) to network B (192.168.10.x) with ip route command

adding routing from one network to other linux with ip route

I had a Linux router which does NAT for a local network located behind a CISCO router receiving internet via its WAN interface routing traffic  to Linux with IP 192.168.1.235. The Linux router has few network interfaces and routes traffic for networks; 192.168.1.0/24 and 192.168.10.0/24. Another Linux with IP 192.168.1.8 had to talk to 192.168.10.0/24 (because it was necessary to be able access  ISCO's router web interface accessible via a local network interface with IP (192.168.10.1). Access to 192.168.10.1 wasn't possible from 192.168.1.8 because routing on NAT-ting Linux (192.168.1.235) to 192.168.10.0/24 network was missing. To make 192.168.1.8 Linux communicate with 192.168.10.1,  had to add following routing rules with ip command on both the Linux with IP 192.168.1.235 and Linux host behind NAT (192.168.1.8).

1. On Server (192.168.1.235) run in root shell and add to /etc/rc.local

# /sbin/ip r add 192.168.10.0/24 via 192.168.1.235
And then copy paste same line before exit 0 in /etc/rc.local

Its good idea always to check routing, after adding anything new, here is mine:
 

# ip r show

192.168.5.0/24 dev eth0  proto kernel  scope link  src 192.168.5.1
192.168.4.0/24 dev eth0  proto kernel  scope link  src 192.168.4.1
192.168.3.0/24 dev eth0  proto kernel  scope link  src 192.168.3.1
192.168.2.0/24 dev eth0  proto kernel  scope link  src 192.168.2.1
192.168.1.0/24 dev eth0  proto kernel  scope link  src 192.168.1.235
192.168.0.0/24 dev eth0  proto kernel  scope link  src 192.168.0.1
192.168.10.0/24 dev eth1  proto kernel  scope link  src 192.168.10.2
default via 192.168.10.1 dev eth1 
 

2. And also on Second Linux host (192.168.1.8) 

# /sbin/ip r add 192.168.10.0/24 via 192.168.1.235
To make routing permanent again paste in /etc/rc.local before exit 0

After above rules, I can normally ping and access hosts on class C network 192.168.10.1-255  from 192.168.1.8.

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